THE ECOLOGY OF A TEMPORARY AND A PERMANENT

POND I N TASPlANIA..

M . Y A S I N ,

ZOOLOGY IV,

. 1967.

Plate 1. Gmnton Lagoon,.'March 1967, vier~ed from the south. '?l?e lagoon which is largely i n a d i y ' s t a t e is in the foregroMd, followed by the River Dement, and the h i l l s i n the

Plate 2. Granton Lagoon, September 1967. The lagoon i s conpletely under water.

Acknowledments .

The study of pond ecology was both interesting

and exciting. Thanks are due to the numerous people,

who contributed to the success of this project, among

whom are: Dr.I.S.Iiilson, my Supervisor, who also read

the manuscript and was a pleasure to work under;

Dr.J.L.Hickman for his general advice and interest in

my work; Dr.W.M.Curtis for her help in the identifica-

tion of the flora; Mr.R.Wheeldon, the laboratory

manager;and Mrs.M.Carter for typing this thesis.

I am indebted to the owners of the ponds who

allowed me to study them: Mr.D.Weeks and Mr.N.Bester,

who owned the Granton Lagoon; The Animals and Birds'

protection Board which also protects the Granton Lagoon

as a private sanctuary; Mr.K.Calvert who owns the

Calvert's Lagoon.

I am grateful to the Australian Colombo Plan

authorities who have sponsored me during this study.

Contents.

I. Summary.

11. An ~colo~ical Study of Granton Lagoon

( ~ e m ~ o r a r ~ pond).

Introduction.

Methods and Results.

Physiochemical Studies.

Biological Observations.

Over summering of organisms.

Discussion.

111. Laboratory Studies.

Cyclomorphosis of Daphnia carinata. 83

The Osmotic Tolerance Range of D, carinata. 83

The Resistance of Ephippia to Desiccation. 84

Some Factors affecting Hatching of Ephippia.88

IV. A Brief Ecological Study of Calvert's Lagoon

(permanent pond).

Introduction. 9 2

Physiochemical Studies. 93

Biological Studies - qualitative. 97

Comparison with Granton Lagoon. 100

V. A Comparison of the Growth Rate of an 103

amphipod, Austrochiltonia australis in the

two ponds.

VI. A Comparison of the Growth Rate of a calanoid, 107

Boeckella triarticulata in the two ponds.

VII. General Discussion.

VIII. References.

General References.

References used for identification of

organisms.

IX. Appendix. 1

Diagram of three dominant Diatoms of

Granton Lagoon.

Raw Data for Granton Lagoon.

Raw Data for Aves of a part of River

Derwent.

I Summary

Two ponds, a temporary and a permanent, were in-

vestigated over a period of 7 months, the study of the

temporary pond being the more detailed. Of the five

physiochemical factors studied, it is improbable that

any one factor caused all the observed biological changes,

yet it seems that the incidence, abundance and succession

of organisms followed temperature and depth of water more

closely than any other factors. Laboratory studies were

conducted to determine oversummcring forms in dry soil.

Ephippia, an oversummering form of Daphnia carinata, was

quite resistant to desiccation. Factors affecting the

hatching of ephippia were also examined. Daphnia itself

was tolerant to a wide range of osmotic pressure. These

observations showed the capacity of an organism well

adapted to the rigors of the environment.

The permanent pond was studied only qualitatively

Its flora and fauna, especially the former, were less

diverse than that of the temporary pond. This was

pr&bably due to high interspecific competition in the per-

manent pond where the organisms appeared to be persistent

unlike the seasonal incidence, abundance and succession of

organisms in the temporary pond which would reduce inter-

specific competition.

The growth rate of a calanoid and a arnphipod were

greater in the temporary pond than in the permanent pond.

This could have been due to differences in trophic

conditions, predation and genetic differences.

I1 An Ecolo~ical Study of Granton La~oon,

A Brackish-water Temporary Pond.

Introduction

Publications of limnological work have been mainly

concerned with large bodies of water; there are only a

few publications concerning ecological studies of

temporary ponds. Overseas workers who have investigated

the latter include Murray ( l 9 l l ) , Peterson (1926) ,

Mozley (1932) , Ward (1940) , Kenk (1949) , Byars (1960) ,

Stout (1964) , Barclay (1966) and Hartland-Rowe (1966).

As yet there has been no published survey of a temporary

pond in Australia.

The main objective of this work was an ecological

study of Granton Lagoon which is a brackish-water

temporary pond. The aims were to investigate the season-

al fluctuations in the numbers and kinds of organisms

inhabiting thc pond, It was intended to record what

species inhabitated the pond and for how long, what range

of physiochemical conditions they met and how they surviv-

ed when the pond dried out in summer.

Reasons for classifyin? Granton Lagoon as "A Brackish-

water Temporary Pond!'

Bayly (1967) stated that the adjective 'brackish'

has had a long multilingual usuage and in a general if not

specific way is widely understood. At a symposium in

Venice in 1958, it was recommended that the use of the

term 'braclcish' should be dropped and 'mixohaline' used

to refer to diluted sea water. From a biological point

of view, it was claimed that it was desirable to distin-

guish waters in which the salinity is approximately the

same as in the sea from those in which it is not. The

Venice System (~e$d, 1961) defines mixohaline as water

with salinity range of 0.5% to 3.0%, inclusive.

Bayly, Hedg~eth and Toffler ( B ~ Y ~ Y , 1967) agreed

that it was undesirable to extend a classification based - on sea-water to inland waters. Toffler ( ~ a ~ l ~ , 1967)

pointed out that the subdivisions of the Venice System

had little meaning for inland waters since the boundaries

between the various organisms are hardly discernable in

a number-of-species-salinity diagram. Nevertheless,

Bayly noted that the term brackish persisted in literature

and claimed that its use will continue and may not be

wholly undesirable. Incidentally, according to the

Venice System, the water of Granton Lagoon qualified as

mixohaline as it had a slainity range of 0.61% to 3.40%

for the period of investigation i.e. from April, 1967 to

October, 1967 inclusive.

Over 90$ of tKe pond becomes completely dry in

summer. Whether it dries out completely or not is con-

troversial. Of the four farmers interviewed, three said

that in severe drought years, which seem to occur every

three or four years, the pond becomes completely dry.

One farmer maintained that it never dries out completely;

there is always a little water at the south-east corner of

the pond where there is a stand of Phragmites close to the

road. The latter admitted that the water present in the

past summers was insignificant.

Although the drought this year has been severe, a

small body of water was present at the south-eastern end

of the pond when I first visited it in March, 1967. Never-

theless, it is quite conceivable that the pond could dry

out completely in summer. Since the controversy concerns

only a very small part of the pond, it may be concluded

that Granton Lagoon is largely a temporary pond with a

very small part of the pond under water permanently. If

the controversy is ignored, the pond is then a complete

temporary pond.

The term pond is universally used, and the common

conception of a pond is generally understood as a small

body of confined waters. Odum (1961) defined a pond as

a small body of water in which the littoral zone is

rclatively large and the limnetic and profundal regions

are small or absent. Welch (1935) defined a pond as a

small, shallow body of standing water in which relatively

quiet water and extensive plant occupancy are common

characteristics. All the characteristics of a pond as

defined by Odum and Welch are present in the Granton

Lagoon.

Thus the Granton Lagoon may justifiably be called

'a brackish-water temporary pond.'

A Brief History of Granton Lagoon.

The pond is situated on a cattle farm at Granton,

about 14 miles north-west of Hobart. It is situated on

the immediate left side of the road leaving from Hobart

to New Norfolk. Prior to the construction of the road,

it was part of the adjacent River Derwent, and formed a

swamp. The road was constructed in the years 1818 and c

1819 (~istorical Records of Australia, 1921). The road

cut off the swamp from the river to form an artificial

pond and since then its only connexion with the river-is

a stormway which passes below the road.

With the construction of the road, a drain was

created bctween the road and the pond. The drain is

separated from the pond by a raised hedgc all along the

length of the pond except at two points, quite apart,

where the hedge has disappeared. casual observation of

the drain revealed numerous human disposals such as

bottles., cans, tyres, food materials etc.

The pond and the adjacent part of the River Derwent

are frequented by waterfowl. On 4 March, 1920, the

Rivers Derwent and Jordan and all flats, marshes and swamps

immediately adjacent to the rivers were officially

declared a sanctuary especially for Black Swan. Although

other waterfowl were not declared protected then, but

they seem to have and still are enjoying the protection

of a sanctuary. (~asmanian Govt. Gazette, 1920).

Shooters then turned their attention to ducks on

the lagoon. Mr. Gould, a former owner of the farm,

resented the shooters and took the matter to the

authorities, The Animals and Birdsi Protection Board.

Both parties decided to turn the lagoon into a sanctuary.

Consequently, it was proclaimed a sanctuary on the 24th

May, 1938. To complete the story concerning the River

Derwent, the 1920 proclamation was reviewed in February,

1941 and the sanctuary was slightly restricted and

defined to extend from Dogshear Point in Glenorchy to

New Norfolk. (~asmanian Govt. Gazette, 1941).

At the north-west end of the pordis a ridge

0ccupied.b~ a few eucalypts, Eucalyptus viminalis, and

some other shrubs. Black ducks breed mainly on trees

and the ridge used to be a breeding ground for the ducks

when there was a large stand of the gum trees. The

trees were felled by man and as the stand thinned out,

the ducks abandoned the ridge as a breeding ground and

have not returned to br-eed here since 195-.

Mr. Gould who lived on the farm from 1919 to 1961

c l a ims t h a t s n a i l s and e e l s were p r e s e n t a t one t ime ,

b u t d isappeared a few y e a r s before he l e f t .

General D e s c r i ~ t i o n of t h e Granton Lagoon.

The pond i s a depressed b a s i n a long the edge of an

o u t e r paddock. I t i s small i n a r e a , about 0.04 square

k i lome te r s (about 10.20 a c r e s ) . I t s o u t l i n e i s b e s t

app rec i a t ed by s tudying t h e map on page 9 ( ~ i g . 1 ) . The

maximum l e n g t h , from e a s t t o west , i s about 319.70 meters

and i t s maximum width from n o r t h t o sou th i s approximately

159.90 meters.

The bottom of t h e pond i s o f s o f t o rgan ic s o i l below

which i s mudstone. A t dep ths va ry ing from about 5 t o

30 cm. below t h e s u r f a c e organic s o i l and mudstone i s a

hard c l a y pan which may se rve t o r e t a i n water . The farm-

l and around r i s e s sha rp ly from t h e pond t o form g e n t l e

s lop ing h i l l s . There a r e two d i s p o s a l grounds l o c a t e d

a long t h e edge of t h e pond. One a t t h e extreme e a s t e r n

end i s used f o r dumping sari-dust and garbage and t h e o t h e r

a t t h e sou thern border f o r d e p o s i t i n g farm animal waste .

The pond a c t s as a dra inage b a s i n i n t o which water

s eeps , undoubtedly b r ing ing Inany n u t r i e n t s from t h e

surrounding land . The pond l i e s i n a r eg ion w i t h an

annual r a i n f a l l of approximately 30 t o 22 inches . During

t h e months when t h e pond was under wate r , t he most f requent

wind encountered was nor th-wester ly and o c c a s i o n a l l y ,

..Fig. 1 - h p of W o n Iagoon, showhg the distribution of surraundfng Vegetation.

& ' A t r i ~ h x hastata J Jw mQ?%%bAM B Ek!m@~. M Mimulus r- B s Buraaria epinosa P R m m i t e s ccemaunls

C Cotuh e. s SS- uef lola D D ~ U ~ distlehophylla T E B u o a ~ u E J ~ ~ I . &fru@;: maritimus

Scale: 1 cm. = 2 5 . 2 meters

westerly or southerly. The pond seems to be well

protectcd from the winds by the surrounding hills. The

deepest part of the pond under water was estimated to be

about 60 cm.

Vegetation.

The pond when filled with water, is characterised

by a dense vegetation of rooted hydrophyte almost over

the entire basin. The hydrophyte, Ruppia maritima, could

have greatly contributed to the general stillness of the

water.

The border of the pond is occupied by numerous

species of plants. A list of the names of the plants

identified is given on pages 1 1 and 12. Some ten or more

minor Angiosperms were not identified.

A map showing the distribution of the primary veget*

tion of the pond is shown on page 9 ( F . 1 ) . A ridge

at the north-west corner is occupied by a small stand of

Eucalyptus viminalis and a few other shrubs including

Bursaria spinosa and Acacia diffusa. Immediately east

of the ridge, is a large stand of a reed Phragmites

communis, a sedge Scirpus maritimus, with scattered clumps

of a rush Jiincus maritimus. Along the eastern border of

the pond are found dense clumps of Juncus maritimus,

*. interspersed with Scirpus maritimus, a grass Distich~lis

. distichlophylla, a camphor Salicornia quinqueflora and

A list of Plants found in Granton Lagoon.

Angiospermae

Monocot- Fam. Ruppiaceae *Ru~pia maritima (L.)

yledoneae: Juncaginaceae *Triglochin striata (~uiz.

8: Pav.)

Graminae *Distichlis . distlchophylla

(Labill.) Fassett.

Eestuca ?arundinacea

(~hreb. )

Vulpia me~alura'(~utt.)

Rydb . Lolium . ?perene (L. )

"Bromus mollis (L.)

*Bronlus diandrus (~0th. )

Agrotis aemula (R.B~.)

Polypogon monspeliensis

(Lj~esf.

*Phragmites communis (~rin)

Cyperaceae *Scirpus maritimus (L.)

Gahnia filum (Labill. ) . F.Muel1.

Juncaceae *Juncus maritimus (Lam.)

:Dicoty-

ledoneae :

Cruciferae Lenidium pseudotasmanium

h hell .)

Pittosporaceae Bursaria spinosa (~av.)

Linaceae Linum marginale (A. ~unn.)

Leguminosae Acacia diffusa (~er.)

Rosaceae - Rosa rubipinosa (L.)

Myrtaceae Eucalyptus viminalis

(Labill. )

Compositae Leptorhynchos 2.

(~essin~.)

Cirsium vulgare (~avi)

Ten. Epacridaceae Astroloma hum:ifusum

(~av.) R.Br.

Pri~nulaceae Samolus re~ens (J.R. &

G. Forst.) Per.

Scrophulariaceae

*Mimulus repens (R.B~.)

Plantaginaceae Plantago a. (L.) Chenopodiaceae *Atri~lex hastata (L.)

*Salicornia quinqueflora

( ~ u n ~ e ex.Ung. Sternb.)

Polygonaceae Rumex obtusifol.ius (L.)

Santalaceae Exocarpos cupressif ermis

(Labill.)

There are some ten or more minor Angiosperms which have

not been identified. Plants with an asterisk form the

primary vegetation.

Mimulus repens and Atri~lex hastata. At the extreme

north-eastern corner is a pure stand of Bhramltes

communis. The rest of thc border is occupied by mixtures

of Sal icorniatquinquef lora , Mimulus repens, Cotula a., Atriplex hastata and Distichlis distichlo~hylla.

Scattered over the pond are some twenty-four small

to very small islands colonized by the primary plants

(except ~hragmites) and some secondary plants.

In thc extreme winter months of June and July,

Salicopnia and ,Atriplex took on a red hue unlike their

normal green colour, due to increascd production of a red

pigment, anthocyanin in response to low temperature.

In spring, ~ghich started in late September and may

continue into November and December, flowering commenced

in most plants. Nearly all the grasses had set seeds by

the middle of November.

The Seasons.

According to the Hobart Weather Bureau, the general

pattern of a year are as follows:-

Summer - December to February,

Autumn - March to May,

Winter - June to August,

Spring - September to November.

The seasonal pattern is not a rigid one in Tasmania for

it varies from year to year. Furthermore, only two

d i s t i n c t seasons , namely summer and w i n t e r , a r e

exper ienced i n Tasmania. For 1967, howcver, t h e seasona l

p a t t e r n based on a i r t empera tures observed a t Granton

Lagoon and New Norfolk, may be taken a s fo l lows: -

Summer - January t o March

Autumn - Apr i l

Winter - May t o September

Spr ing - October t o .... The temperature changes a t t h e two p l accs a r e shown on

a . graph on page 15 ( ~ i ~ . 2) and i t shows t h a t t hey a r e

c o r r e l a t e d . New Norfolk i s a town about 12 mi l e s west

of Granton Lagoon and i s t h e n e a r e s t p l a c e which maintained

complete d a i l y temperature r eco rd ings up t o d a t e .

Methods and R e s u l t s .

The pond was v i s i t e d every two weeks between March

and J u l y , i n c l u s i v e . During t h i s pe r iod , two a d d i t i o n a l

v i s i t s were made on March 2 6 , and J u l y 3 , fo l lowing heavy

r a i n f a l l . From August t o October, i n c l u s i v e , t h e v i s i t -

i n g i n t e r v a l was extended t o every t h r e e weeks. During

t h e s e v i s i t s , t h e fo l lowing procedures were undertaken.

1 ) On a r r i v a l a t t h e pond a t about 11.00 am, E a s t e r n

Standard Time, t h e cond i t i on of t h e sky and t h e

wind were noted.

2) The spec i e s and numbers of b i r d s i n and around t h e

pond were noted.

3 ) Readings of dep th of the pond, a i r and water

' -61 & 'r ~ i r Temp. of Granton Iagoon and New Norfolk, 1967.

-_A_--

- Granton Iagoon, temp. on Sampling Days. New Norfolk, Av. Monthly Temp.

temperatures, and oxygen tension of water were

taken.

4) Water samples were taken for both population

estimations and chemical studies, from eight regions

of the pond. The map on page 18 ( ~ i ~ . 3) shows

the arbitrary divisions of thc pond into the eight

regions which include the drain beside the road.

5) The species and numbers of birds were noted again

and the visit concluded.

Physiochemical Studies.

a) Weather

The list below gives the dates of sampling with a

brief comment on the - condition of the sky and wind - weather noted at 11.00 am Eastern Standard.

Time.

Date sky Wind

7-4-67 Sunny, Patches of cloud Southerly, strong.

20-4-67 Slightly overcast N . W . , strong.

26-4-67 Sunny, Patches of cloud N .V., moderate.

3-5-67 Sunny, clear sky N.W., moderate.

18-5-67 Overcast - 5-6-67 Sunny, clear sky N.W., moderate.

26-6-67 Sunny, Pathhes of cloud N.W., light.

3-7-67 Sunny, clear sky S, light.

24-7-67 Overcast N.W., l i g h t .

14-8-67 Sunny, l a r g e pa tches N.W. , moderate.

of cloud

5-9-67 Sunny, c l e a r sky -

26-9-67 Sunny, pa t ches of cloud N.N. , moderate.

16-10-67 Sunny, c l e a r sky N.W., moderate.

b ) Depth of t h e Pond

To o b t a i n dep th read ing , a wooden meter p o s t ,

graduated t o t h e n e a r e s t 2 cin. w a s sunk i n t o t h e

ground a t t h e sou th e a s t end where t he pond w a s

dry . The graph on page 19 ( ~ i ~ . 4) shows t h e

changes i n t h e d e p t h of t he pond. On t h e same

graph i s p l o t t e d t h e average monthly r a i n f a l l f o r

t h e township of New Norfolk. From these g raphs ,

i t could be seen t h a t t h e depth v a r i e d d i r e c t l y

w i t h t h e r a i n f a l l . The maximum'depth recorded was

34 cm. on September 5 and 26. C e r t a i n p a r t s of t h e

pond, e s p e c i a l l y t h e no r th -eas t end, approached a

dep th of 60 cm. d u r i n g September.

R a i n f a l l was t h e main f a c t o r c o n t r o l l i n g t h e

dep th . Other minor f a c t o r s such a s t h e l e v e l of

t h e water t a b l e , evapora t ion and outflow i n t o t h e

r i v c r could a f f e c t t h e depth. There was l i t t l e o r

no in f low from t h e r i v e r because no v a l i d c o r r e l a t i o n

could be drawn between t h e t i d e s of t h e liver and t h e

Fig. , 3 - - Division of Gmnton Lagoon into 8 arbitrary Regions for the purpose of Sampling. Nap a lso shom progressive extension of Water.

D = Drain Extent of Water on the following Dates: I

7.L.67 . - . .. . . . -. - . .. . . . . I

.26.4.67 .>.. :..:i _..* %. .. 18.5.67 '

.."?! ..., ,,*:.-,::,.. -.< - - \.. , I 26.6.67 whole pond under water.

I

Fig. 4 - Graphs of Depth and Rainfal l against Time, 1967.

- _ L - - L - * - L _ - Depth i n GM. Av. Monthly Rainfall f o r NeG Norfolk.

Fig. 5 -Graph of Monthly Max. High Tide f o r Hobart, 1967.

. .g r . ,I--7T.--- -----7-

, .

I

6

Tide

-

in - ~7 4 FT.

4 , .

I

. , - -! . ,

i - i

A M J . J A S 0

Month

depth of t h e pond. A graph of t h e monthly maxim-

un h i g h high- t i d e recorded a t Hobart by t h e

Hobart Marine Board i s given on page 19 (Fig. 5 ) .

The t i d e s reach Granton an hour l a t e r than Hobart.

It may seem from t h e graph, t h a t t h e r i s e i n t i d e

from 6 f t , i n M a y t o 6.7 f t . i n J u l y may have

caused t h e i n c r e a s e i n dep th of t h e pond through

inf low. But when t h e t i d e drops t o 6 f t . i n

August, t h e depth of t h e pond i n c r e a s e s s l i g h t l y

i n d i c a t i n g t h a t i t s dep th i s independcnt of t h e t ides .

Furthermore, a s we s h a l l s ee l a t e r , t h e c h l o r i n i t y

of t h e two waters d i f f e r e d markedly.

e ) Temperature.

A Protechmeter (Model SM120) was used t o measure

temperatures and r ead ings were always taken a t

11.30 am. Eas t e rn Standard Time. P r i o r t o May 1 8 t h

sampling, t h e tempera tures were recorded a t a f i x c d

spo t l o c a t e d i n r eg ion 6 ( t h e water was conf ined t o

t h i s r e g i o n ) . On May 1 8 t h , n e a r l y t h e whole pond

was found t o be under water and a new p o s i t i o n i n

r eg ion 2 which was c l o s e r t o t h e c e n t r e of t h e pond

was chosen t o measure temperatures . A t bo th

l o c a t i o n s , a i r temperature w a s recorded i n t h e shade

and 6 cm. above t h e water su r f ace . Water temperat-

u r e s were recorded a t two d i f f e r e n t l e v e l s - 2 cm.

below the water surface and 2 cm. above the bottom

surf ace.

The results are graphed on page 22 (~ig. 6).

There is a very close correlation between the air

and water temperatures throughout the period of

investigation, except on August 14th, where there

is a significant difference. It was a day when

c1,oud shadows moved across the pond every few

minutes and were probably the cause of the observed

difference.

In most cases, the water temperatures at the

bottom were slightly lower than near the water

surf ace. Although these differences are non-

significant, but it is quite conceivable that

microthermoclines could appear in restricted parts

of the pond on calm days. Such was the case on

July 24th, a overcast day with light north westerly

and preceded by a cold morning, a distinct micro-

thermocline was observed in the region 2 D, a drain.

A graph showing the microthermocline is shown on

page 23 (Fig. 7). $he thermocline can be seen to

1) decline steadily from 0 to the 5 cm. depth,

2) drop moderately sharp from 5 to 25 cm. depth,

3) increase moderately sharp from 25 to 40 cm. depth, and

4) increase slightly, 1 cm. below the soil surface.

6 - Graphs of Temperature, O c against Time, Granton Iagoon, 1967.

A i r Temp.- &m. above the water surface.

Waterlemp.- 2cm. below the water surface.

. . '

'water Temp.- 2cm. above the bottom subface. , ..-.--T.- --T-

10 -

-

Fig. 7 -Temperature and Oxygen Tensionagainst Depth, Granton lagoon, July, 24,1967.

Depth in 20 CH.

4 Uater Surface

I

4 S o i l Surface

This is an interesting type of microthermocline.

Above 25 cm. depth, it forms a typical thermocline,

and below thc 25 cm. depth, the tempcrature in-

creases. This phenomenon may be attributed to the

presenoe of dense vegetation and with littlc or no

effect from the wind, the waters remained unmixed

with thc surface layer following the rising air

tempcrature. Apart from the physical reason, the

increase in tempcrature below the 25 cm. depth may

due' to biological activity. Metabolic activities

by aggregated organisms below this level and

decomposition processes may have contributed to the

rise in tempcrature. The higher temperature 1 cm.

below the soil surface than that just above the soil

suggest higher biological activity in the soil too.

Maximum and minimum recorded values were as

follows: - Air temperature Maximum: 23.0'~ on April 7

Minimum : 4.9'~ on ~ u l y 3

Water temperature

2 cm. below water surface,

Maximum : 21 . ~ O C on April 7

Minimum : 4.5'~ on ~ u l y 3

2 cm. above soil surface,

Maximum : 15.9'~ on October 10

Minimum : 5.1°c on July 3

d) Light Penetration.

A Secchi disk (welch, 1948) of diameter 4 cm.,

was used to determine the limit of visibility.

Although the water was visibly turbid, light

was able to penetrate to the bottom in all parts

of the pond tested throughout the period of

investigation.

The colour of the water was generally light

gree.n. The pond was fully exposed to the sun

throughout the year.

e) Dissolved Oxygen.

The Protechmeter which was used for temperature

recording, also measured dissolved oxygen tension

in the water. The meter was used to record

oxygen tension until the last measurement in July,

after which it was used only to measure temperature.

The subsequent method employed to estimate oxygen

tension was the Winkler method. In this method,

reagents were added out in the field and the

sample taken back to the laboratory for titration.'

Oxygen concentration were taken at the same spots

as for the temperature and the measurements were

made immediately after recording the temperature.

Oxygen tensions were also recorded at two water

levels namely 2 cm. below thc water surface and 2 c m

above the soil surface. The resulting graph toolc

the form shown on page 27 (Fig. 8). The observed

values were recorded in parts per millian. These

values can be transformed into percentage saturation

to give a better indication of what has been

happening in a sample of water. For transformation

a table giving solubility of oxygen in known saline

waters at a given temperature (American Public Heal&

Association, 1960) was used and the resulting data

is plotted on the same graph on page 27 (Fig. 8).

Values, recorded in the early stages of sampling,

were generally low. After the sixth sampling, the

values were high. This ivas undoubtedly due to

photosynthetic activity of the dense hydrophyte

causing supersaturation aided by the prevailing low

temperatures. The maxim um value recorded was % 132% on August 14th. There are two significant

drops of the oxygen tension, on May lath, and July

24th. These drops could have been caused by the

high water temperature on these days, and it may

also have been significant that the skies were over-

cast on both days.

No difference was observed between the oxygen

tension near the water surface and that near the

soil- surface in a11 sampling days except July 24th.

A M J J A S . 0

Month

On that day, the oxygen tension near the water

surface was 73% while it was 51% near the soil

surface. It was on the same day the micro-

thermocline was recorded. At the same location

where the microthermocline was recorded, the oxygen

tension at the various levels w#e noted too. The

resulting data are plotted on the same graph as the

microthermocline on page 23 (F'ig. 7). Thc graph

shows that the oxygen tension falls from 9.60 ppm

at a 5 cm. depth to 9.50 ppm at 25 cm. depth, a

relatively small fall. Below 25 cm., there is a

sharp fall. to 8.20 ppm at a depth of 40 cm.

Together with the microthermocline, the oxygen

decline forms an interesting observation. The

higher oxygen tension above 25 cm. may be attributed

to photosynthetic activity. The lower oxygen

tension below 25 cm. may be due to the higher

temperature. Furthermore, below this level, there

could have been a high aggregation of animals and

their resulting high metabolism together with de-

composition processes may have depleted the oxygen.

f) Hydrogen Ion Concentration and Chlorinity.

Hydrogen Ion Concentration (PI-I)

A sample of water was taken from each region of

the pond to determine the pH and chlorinity. These

values were determined in the laboratory. Al-

though the measurements were done on the same day

of sampling and immediately on returning to the

laboratory the pH would have ~hanged~undoubtedly~

due to biological activity during transit.

pH was measured with a pH meter (~etrohm Model

~350A). The values of the samples obtained are

averaged on each occasion and the resulting data

are graphically represented on page 30 ( ~ i ~ . 9).

The water was always alkaline. The graph shows a

steady rise from pH 7.36 in April to 9.08 in July.

This rise could be due to the increased release of ? C

carbon dioxide by plants and algae which photo-

synthesize. The pH then dropped to 7.70 in August,

probably caused by decrease in photosynthe bsls, r / 4 . brought about by low temperature. The pH rises

again to about 9.00 in October with increasing

temperature.

pH varied from one part of the pond to another

on all occasions e.g.

Region 1 2 2D 3 4 5 6 6D

July, 24 8.41 8.65 7.60 8.50 8.69 8.30 7.70 7.45

October, 16 8.65 9.25 8.99 9.20 9.14 8.85 8.89 861

This variation could be due to a difference in the

degree of biological activity from one part of the

Fig . 9 - Graph of av. against ~ & e , f6r Granton Iagoon, 1967.

I I I I I 1 1 1

F i g . 10 - Gmph of pH againat Time, recorded &$t Region 6 of Granton Iagoon, 1969.

9

I I , ,

-0p -

6

fl L ~ ! - A H I J Month J A S 0

pond to another.

The changes in pH recorded at a particular

position such as at Region 6 is graphed on page 30

( ~ i ~ . 10) and shows that it correlates well with

the average pH trend except for the value on June

5th. The slightly different, but correlated

trends in pH for'different parts of the pond in-

dicate differences in the magnitude of biological

activity.

Chlorinity

~hhe chlorinity of water samples were determined

by titration. l'he average chlorinity on each

occasion is graphed on page 32 ( ~ i ~ . 11). ' The

graph shows a sharp increase in chlorinity on

April 26th reaching a maximum of 3.47 gm/lit. This

happened following a whole day of rainfall, 15 points

recorded at New.Norfolk, which could have washed 0

nutrients rich in chloride ions into the pond..

The rainfall increased the area of the pond under

water (see map on page 18 (Fig.3) ) and consequently

dissolved the salts of the newly submerged area.

Following a heavy rainfall on July 1st and 2nd, 93

points recorded at New Norfolk, the chlorinity

decreased slightly. from 1.90 to 1.72 gm/lit.,

probably due to dilution.

FQ. 11 - Graph of Av. Chlor in i ty against Time, f o r Granton lagoon, 1967.

0 I I I

Arrow ind ica tes heavy Rainfall.

Fig. 12 - Crllaph of Chlor in i ty a g a i n s t T h o , recorded a t Region 6 of Gmnton Lagoon, 1967.

A S A M J J 0 Month . .

Like the pH, the chlorinity varied from one

region to another region of the pond, e.g.

Region 1 2 2D 3 4 5 6 60

July, 24 1.79 1.76 1.78 1.71 1.75 1.65 1.57 1.49

October, 16 2.27 2.10 1.62 1.56 1.50 1.25 1.23 067

The chlorinity changes between regions were

slightly different and a graph on page 32 (~i~.l2)

shows the chlorinity fluctuations at Region 6.

This graph correlates closely with that for the

average chlorinity.

The chlorinity of the River Derwent immediately

adjacent to the Granton Lagoon was determined on

two occasions for comparison:-

River Derwent Granton Lagoon

September, 5 2.52 p/lit. 1.59 gm/lit.

October, 16 5.00 " 1.65 "

The results indicate that the chlorinity of the

two regions differ markedly and suggests that there

is little or no influx of water from the river into

the pond. An outflow from the pond into the river

is more likely, which is the very purpose of the

stormway.

Chemical Analysis.

The following tabulation shows the results of the

only chemical analysis performed on a sample of water

from Granton Lagoon collected on November 11th.

~ a + 1950 ppm

K + 36 " 2+ Ca 28 " 2+

Si 3 "

CL- 2360 "

Total dissolved organic solutes 1 100 ppm

I I I! inorganic " 4000 "

. II solutes 5100 "

Na, K and Ca were determined by flame photometer, Si and

C1;. by chemical methods and dissolved solutes by evapora-

tion-muffling method.

A chemical analysis in the early part of the year

would have served to reveal any changes in the water

composition, but this was not done. Nevertheless, the

high abundance of Euglena and chlamydornona; which are /J

characteristic of water, rich in organic contents

(~utchinson, 1967) in the early period of the year suggests

a higher organic content than the present one.

Bio log ica l Observat ions and Seasonal Abundance.

Two methods of sampling were employed t o s tudy t h e

popu la t ion dynamics of t h e va r ious s p e c i e s i n t h e pond.

F i r s t l y , a sweep n e t t echnique was used t o sample p e l a g i c

organisms. The n e t was made of nylon c l o t h , w i t h a

mesh dimension of 5 7 6 h by 6 6 2 k , and a t t a c h e d t o a l i g h t

s t e e l frame. The mouth of t h e n e t was 10.5 cm. by 14.5

cm. and t h e maximum dep th of t h e n e t was 12.0 cm. Second-

l y , t h e method used t o sample ben th i c organisms was t o

s i n k a c y l i n d e r , open a t bo th ends, u p r i g h t about 2 cm.

deep i n t o t h e mud and then a d i s c was in t roduced benea th

t h e c y l i n d e r which then gave a sample of mud.

A water and a mud sample w a s c o l l e c t e d from each

reg ion . Sub-sampling a t each r eg ion w a s a t random and

s i x t o twelve sub-samples were taken and combined i n t o

one. For p e l a g i c organisms, s t r a t i f i e d samples were

c o l l e c t e d .

The samples were brought back t o t h e l a b o r a t o r y f o r

q u a l i t a t i v e and q u a n t i t a t i v e s t u d i e s . I n t h e l a b o r a t o r y

t h e co lou r of t h e water was noted. The water w a s t hen

examined microscopica l ly and t h e abundance of a l g a e and

pro tozoa expressed i n r e l a t i v e terms of none, few,

moderate, abundant and Bery abundant. Only t h e dominant

a l g a e and protozoans were considered. The r o t i f e r s were

s tud ied under a s t e r eo~n ic roscope which was a l s o used f o r

other small organisms when necessary. The abundance of

macroscopic algae and hydrophytes were noted in the field.

A list of all the organisms encountered is given on pages

41-47. The main species are marked by an asterisk.

Algae.

/ The qualitative results of algae js cxpressed

graphically on page 37 (~i~.l3). The graph shows that

the algae could be classified into two groups - those which persistcd for the duration of investigation and

those which were seasonal. Oscillatoria, Euglena and

Diatom Sp. 1 were present all the time and the rcst were

seasonal. The persistent ones were dominant in late

autumn. The seasonal species had quite distinct

dominant periods and this is best shown by a table:-

Early winter (~une) - Chlamydomonadaceae

Mid winter (~uly) - Diatom Sp. 2

Late winter (sePternber)- Spirogyra

Early spring (~ctober) - Enteromorpha

Organisms can be designated as oligothermal,

polythermal or eurythermal, according to whether they

appear to be cold requiring, warmth requiring, or able

to tolerate a wide range of temperature (~uttner, 1 9 5 3 ) .

This is just another form of classification and is quite

similar and correlated to our classification with respect

to seasons.

Plg . 13 - Temporal dis t r ibu t ion and r e l a t i ve abundance of Algae, Gxanton Lagoon, 1967.

2 - j Nitel la 9. -

0 I

Spirogy-ra - sp.

0

- 2 - _ Diatom, Sp. 2 - - 0 4 - -

2 = = . = = = . = '

Euglena ?vi r id i s

LAI~-.L~ s d Month

Colour of Waterr c = colourless, lg = l i g h t green, g =green. Ordinate: 0 = none, 1 = few, 2 = modemte, ,3 = abundant, 4 = very sbunctsnt.

Returning to the graph, it indicates that there

was a succession of algae. Different species would

undoubtedly have different temperature, light, nutrients

and other requirements, and it could be that a particu-

lar species predominates at a particular season because

the prevailing conditions are favourable. Predation

or selective grazing by higher organisms and parasitism

may have important effects on succession. The two

preceding statements are important ones and should be

recalled to mind in future observation of succession

and dominance.

There are four other points to note. Firstly, the

water was generally green or light green in colour, but

in late winter (~e~tenber), with Spiro~~ra and Ruppia at

their dominance, the water was colourless. Secondly,

following its peak abundance, S ~ i r n w commenced spore

production in Spring. Thirdly, Famphonema a diatom, was

found epiphytic on Oedogonium. Lastly, a fungus,

Saprolegniaceae was twice observed growing on dead organ-

isms. ( ~ i ~ . 32 on page 122.shows 3 dominant species of

diatoms at Granton Lagoon.)

Protozoans, Rotifers and Nemata.

Like the algae, these animals were studied qualit-

atively. The temporal distribution and relative

abundance of the main ciliates, rotifers and nematodes

are graphed on page 39 ( ~ i ~ . 14 ) . The graph indicates

Fig. 14 - Temporal dis t r ibu t ion and r e l a t ive abundance of Ciliates, Rotifem, and Nemta, Granton Lagoon, 1967.

Branchionus Q. 2 ( ~ o t i f e r , Sp. 1)

0

Nennr ta (Nemtod)

Rotifer, Sp. 4

-

h m e c i u m =. 00

I L -

A M J J A S 0 Month

W i n a t e : 0 none, 1 = few, 2 = mocierate, 3 = abundant+ 4 = very a b W n t .

4

2

0 . 4

2

o

- - - - I - - - -

Rotifer, Sp. 3

1 Rotifer, Sp. 2

i I

that there was succession and dominance and this can be

best expressed by tabulation:-

Autumn ( ~ ~ r i l ) - Paramecium, Branchionus (sp. 1) and Nematode,

Early winter ( ~ a ~ ) - Rotifer Sp. 2 and 3, (~une) - Stylonychia and Rotifer Sp. 4,

Mid winter (~uly) - Rotifer Sp. 1.

All the above species were relatively short-lived

except for Rotifer Sp.1 which was present from April

to August, inclusive. The rest were present only for

two to three months and were gone by early July (mid-

winter).

Minute protozoans and bacteria were omnipresent

for the duration of investigation.

1 Platyhemintes, Annelids, Crustaceans and Insects.

Unlike the early organisms, these animals were

studied quantitatively. When an animal was present in

a water sample in low abundance, the whole sarr~ple was

screened. Iihen it was numerous, sub-samples were taken:for

enumeration. The number of sub-samples taken varied

from two to four and was governed by the relative abund-

ance of the particular animal. Since no preservative

reagents were added to the samples when collected, the

naup!lii and young stages of organisms especially those of .

crustacea were ignored in the counting for a portion or

A list of organisms encountered at Granton Lagoon.

Bacteria

Micrococcus and Spirillum forms

Fungi

Class: Phycomycetes Family: Saprolegniaceae 1 sp.

Cyanophyta

Family: Oscillatoriaceae

*Oscillatoria Vaucher

Family: Nostocaceae

Anabaena Bory

Chlorophyta

Class: Chlorophyceae Family: Desmidiacea 3 SPP.

Family: Chlamydornanadaccae 1 sp.

Family: Zygnemataceae

"Spirogyra Link

: Ulvceae

"Enteromorpha Link

Monostroma Thuret

: Oedogoniaceae

Oedoffonium Link

: Characeae

*Nitella Agardh

Chrysophyta

Class: Bacillariophyceae *g spp. of Diatoms - Diatom sp. 1 , 2 and 3

Gamphonema Hust.

Protozoa

Class: Rhizopoda Family: Chaosidae

Chaos Linnaeus (=~rnoeba

Cilioplhora Family: Paramecidae ~hrenber~)

Paramecium Hill

Oxytrichidae

Stylonychia Ehrenberg

Vorticellidae

Vorticella Linnaeus

Four other species of ciliates including one species

with endosymbiotic zoochlorella.were present.

Rotifera

Class: MonogonOntta *Branchionus - Pallas ( ~ o t i ~ e r

Sp.1)

*Rotifer Sp. 2, 3 and 4 e

Nemitirtea (~ematodes)

. . *Nematode :

Turbellaria

Class: Tricladida Family: Macrostomidae

Sp. 1 and *Sp. 2

Annelida

Class: Oligochaeta Family: Tubificidae

"1 sp.

C1: Crustacea Or: Cladocena Fam: Daphnidae

*Daphnia carinata

King, 18.53.

Fam: Macrothricidae

*hfacrothrix burstalis

Smith, 1909.

Fam: Chydoridae

Or: Ostracoda

*Alonel.la nasuta

Smith, 1909.

*Sp. 1 (?candonini)

*Sp. 2 (?cyclocyprini)

and possibly two mon).

Copepoda Fam: Cyclopoida

+Cyclops (0.F~fuller)

Fam: Centropagidae

*Boeclcella triart icukda

(~homson)

Amphipoda Fam: 11y'alellidae

australis Sayce,l901.

C1: Insecta Or: Collembola Fam: Myoniidae Salmon,

.1:945.

* I sp.

Odonata Fam: Cestidae

Hemiptera Fam: Notonectidae *1 sp.

Fam: Corixidae * I sp.

and another spec i e s of Hemiptera.

Coleoptera Fam: Dys t i sc idae

/ Lame: ~ y - p h ~ d r . u s ,/ I-

Hydaticus

Hydrobius

Fam: Hydrophil idae

Larvae: Berosus aus t la l i s

Adul ts : *Rhantus s. sp . 1

sp . 2

T r i chop te ra

Fam: Limnophilidae

1 sp.

O r : D ip t e ra Fam: Tipu l idae 1 sp.

l a r v a e . Fam: Cul ic idae

*Aedes camptorhyncus

Thomson, 1868.

Fam: Chironomidae

*Chironomons Pfeigen

* 7 Tanypus sp.

sp. 3 .

Fam: Ephydridae * 1 sp.

Fam: S t r a t i omyi idae 1 sp.

Fam: Hydrachnidae

Hydrar.achna . Hermann 1934.

A list of Vertebrates found at Granton Lagoon. The

vernacular names are given after the scientific names.

The main species are asterisked.

Fish

C1: Osteichthyes 1-,;

Fam: Pseudaphritidae Pseuda~hihitj-dae bursinus k'

( ~ F i e r 'and Valenciennes. 1830)

Copgolli, Tupong, Sandy or

Freshwater Flathead.

Frog

C1: Amphibia

Fam: Hylidae H I 3 ewingi (~umeril and ~ibron)

Ewing's Tree Frog

: Leptod- Lirnnodynastes dorsalis ( ~ r a ~ )

ac tylidae Bullfrog

Limnodynastes peroni (~urmenil and

~ibron)

Strkped Marsh Frog

Snake

C1: Reptilia

Fam: Colubridae Notechis scutatus (peters)

Tiger Snake

Birds

C1: Aves

Fam: Charadriidae "Lobibyx novae-hollandiae (steph.)

Spur-winged Plover

Fam: Laridae *Larus novae-hollandiae (~teph.)

Silver Gull

Fam: Gallinulidae "Tribonyx mortierii (DU Bus.)

Native Hen

"Porphyrio melanotus (Tensm.)

Bald Coot

Fam: Areidae Notophoyx novae-hollandiae (~ath.)

White-faced Heron or Blue Crane

Fam: Anatidae w'rhynchotis antha ham)

Blue-winged Shoveler

*- castanea (~yton)

Chestnut Teal

*- suDercilijsa (~melin) ,-.

Black Duck

/ "Cygnus atratus a ant ham) /

Black Swan /C

Fam: Falconidae Circus approximans (~eale)

Swamp Hawk

Fam: Hirundinidae "Hylochelidon ni~ricans (vieill)

Tree-Martin

Fam: Corvidae Corvus mellon/i (~athews) L

/-f Raven or Crow

Fam: Fringillidae Passer domesticus do inn.)

House Sparrow

Fam: Sturnidae *Sturnus vulnaris (L.)

Starling

Farn: Musicapidae +Epthianura a l b i f r o n s ( ~ a r d . and

Chat ~ e 1 . b ~ )

Rabbi t

C 1 : Mammalia

1 I . Farn: Tepon~dae Oryctolagus cuniculus inn.) / /

Rabbi t . .

the whole of it could have been generated while awaiting

screening.

Graphs showing the distribution and abundance of

the Platyhelminthes, Annelid crustaceans and the insects

are shown on pages 49, 50 and 51 ( ~ i ~ s . 15, 1.6 and 1 7 )

respectively.

Platyhelminthes and Annelids.

Two species of Platyhelminthes (flatworms) were

encountered. The minor one, Macrostornidae Sp. 1 was

present in small numbers in the early part of the year.

Macrostidae Sp. 2 was absent in autumn and early winter,

but was present for the rest of the period.

A Tubificid species, belonging to the Annelids was

a ~ersistent species and a benthic one associated with

the chironornids.

Crustaceans.

The crustaceans may be divided into persistent and

non-persistent groups. Except for Macrothrix, Alonella

and Ostracod Sp. lwhich appear to be polythermal, the

rest were persistent species. Although the graph shows

that the Macrothrix was low in spring and decreasing, b t J a visit in November and early December indicated it was

on the increase. It is an animal adapted to live at

higher temperatures than the related species, Daphnia.

In a laboratory experiment, separate cultures of both were

15 -Temporal d i s t r i b u t i o n and abundance of a Annelid and a Phtphelminthes, Granton lagoon, 1967.

, I 1

A M J J A S 0 Month

Fig. 16 - Temporal distribution and abundanue of Crustaca, Cmnton lagoon, 1967.

4 I I , I I I I I

Austrochiltonia austral is 2 i i : 001 2 Cyclops 2.

"

Boeckella ttiarticulata

Ostracod, Sp. 2 (Cyclocyprini)

='GO

100. - -

2 - - Ostracod, Sp. 1 (Candonini) -

0 " ---- -

2 - i

Daphnia carinata

-

2 - hcrothrix burstali_s

- - A 1 1 1

'Alonella -ta

J 121 A

Plonth

Fig. 17 - Temporal distribution and aburdance of Insecta, Granton Iagoon, 1967.

Aedes . 2 -

- =XI0 No.

. i Collembilid

0

2 Rhantus sp. -

i

0 --

L A I - 4 J . Month

4 . Density l e s s than 1 per 10 cc. A Density greater than preceding reading.

kept at 15'~ and 25'~. While Macrothrix thrived at both

temperatures, Daphnia thrived at 1 5 O ~ and could survive at

25'~ if the water was aerated. This indicated that the

0 oxygen tension at 25 C was insufficient for Daphnia. Al-

0 though Macrothrix survived at 15 C in the laboratory, b b

it was never observed in the pond during winter and this

could be due to factors such as light, food, competition

for food and space between thc two species etc. in addition

to the temperature and its resulting effect on oxygen in

water.

Insects.

The insects could be divided into 3 forms, namely,

Persistent species - Chironomus, Chironomid anypus pus a.) / . . and Collepb~lld,

Pure 'Winter species - Aedes, Ephydridae and Rhantus Non Winter species - Notonecticid and Corixid. A visit in November and December indicated that the

Notonecticid and Corix.ia. were on the increase. Aedes,

a mosquito larva, was a problem in sampling. As soon as

the water was disturbed, these larvae generally suspending

from the lower surface of the water, swgm to the bottom of

the pond. This usually resulted in a lower estimation

of the population, but the error involved is believed to

be constant.

In nearly all sampling, the species diversity and

abundance varied from one region of the pond to another.

This can be exemplified by studying a part of the results

of sampling on ~ u l L 24th. shown below:-

Region 1 3 6D

Macrostomidae Sp.2 8.34 - - Tubicif id -

Dauhnia 2.53

Ostracod Sp. 2 - Cyclops

Boeclcella

Austrochiltonia

~orixid

Chironomus

Aedes

Ephydridae

Hydrarachna - - t

The figures represent density i.e. n~unber per 100 cc.

1nterrAation between the physiochemical factors and the

incidence and abundance of organisms considered so far.

Apart from temperature and depth of water, it is not

casy to find correlations between the remaining factors

and the incidence and abundance of organisms. The

inc idence of t he organisms were c l a s s i f i e d according t o

seasons which i n t u r n were based on temperature. Tempera-

t u r e could be an impor tan t f a c t o r , bu t need n o t a l w a y s

be so. Close ly a l l i e d wi th temperature a r e d u r a t i o n of

i l l u m i n a t i o n and r a i n f a l l ; t h e l a t t e r governing t h e

dep th of water . P r o p e r t i e s a s soc i a t ed w i t h wate r were

t h e d i s s o l v e d oxygen t e n s i o n , pH and c h l o r i n i t y . It

seems t h a t no one f a c t o r caused a l l t he observed changes,

y e t i t appears t h a t inc idence and abundance followed t h e

temperature and depth of water more c l o s e l y than any o t h e r

f a c t o r s . Pe te rson (1926) and Barclay (1966) a r e of

s i m i l a r op in ion and have suggested t h a t oxygen and pH

followed r a t h e r than caused t h e changes.

P i s c e s .

I n t h e mud samples from reg ion 6 D , c o l l e c t e d 6n

April . 26 th , and May 18 th , t h r e e f i s h e s were p r e s e n t .

These were a l l a e s t i v a t i n g . They were a l l of t h e same

s p e c i e s P s e u d a p h r i t i s b u r s i n u s and were l e s s than 11.0 cm.

Following t h e s e c a p t u r e s , a wi re gauze n e t was b a i t e d a n d '

p laced i n t h i s r eg ion on sampling days , bu t none was

caught. A mo t i l e f i s h was ohserved on October 16 th .

Amphibians.

Frogs were never observed, bu t t h e i r c a l l s were

heard on September 2 6 t h . , and t h e r e a f t e r . Three s p e c i e s

were i d e n t i f i e d by Dr.J.L.Hickman, hased on a tape-

recording of their calls. The three species were Hy&a

ewinffi, Li~nnodynastes dorsalis and L, peroni. . . Their

presence at the pond at this time suggest breeding and

feeding activities. Littlejohn (1963) has recorded

thatg. ewingi bred from April to December while the

other two species bred from September to December.

Reptilia.

A snake was twice observed in October and November

among the sedges and reeds near the ridge. It was a

Tiger Snake, Notechis scutatus, about three feet long.

It is known to feed on frogs, young of Native Hens and

eggs of waterfowl, etc.

Mammalia. ( \ Occasionally, a rabbit or two were sighted on the

fringes of the pond.

m. As was stated earlier, the birds, including the

waterfowl werc counted at 1 1 a.m. and about 4 p.m. on

every visit to the pond. Ifhen the birds were present in

large numbers and moving about, they were counted thrice

and the average taken. The counts made in the morning

are graphed on page 56 (~ig. 18). The counts made in

the evening were ignored because my presence could have

been disturbing to the birds as a whole: The waterfowl

were quite wary and on nearly all occasions flew to the

Fig . 18 -Temporal distribution and abundance of Aves, Granton' Iagoon, 1967.

w- ' I I---

Log ,o No.

I

Swan

! Chestnut 1' - Teal 4

.

Chat i 0

t 4 i Silver

Or- t 2LL -. hll -7 1 1

I Starling 1

/ i

II.__L___(..~ A A M J J A S 0

Month

r i v e r - s i d e when approached.

Only t h e main s p e c i e s a r e shown on t h e graph which

i n c l u d e s P love r s , G u l l s , S t a r l i n g s , Chats , Tea l , Black

Ducks, Black Swans and Tree-Martins. The graph i n d i c a t e s

t h a t P lovers and G u l l s were g e n e r a l l y a permanent f e a t u r e

of t h e pond while S t a r l i n g s and Chats were a t l e a s t absent

i n mid-winter. The waterfowl , namely Tea l and Black

Ducks increased i n numbers ::.as t h e e x t e n t and dep th of t he

water i n t h e pond inc reased . A pai r o f Blnak Swans

a r r i v e d i n mid-winter and t h e Tree-Maptins a r r i v e d i n

l a t e w in t e r .

Apart from t h e s e b i r d s , t h e r e were khe Nat ive Hens

and Bald Coots which ue re permanent r e s i d e n t s of t h e pond.

Vhite-faced Herons, Blue-winged Shove le rs , Swamp Hawks,

Ravens and House Sparrows were occas iona l v i s i t o r s t o

t h e pond.

The pond was used a s a f eed ing , r e s t i n g , c l ean ing

and breed ing ground by the b i r d s . Gu l l s have been

observed t o s tand i n Mn shal low water and t r e a d mud which

was then followed qu ick ly by s t r i k i n g t h e water with t h e i r

b e a k s . . Treading probably r e l e a s e d ben th i c organisms

e s p e c i a l l y t h e chironomid l a r v a e which u e r e t hen picked

up. The Ducks and Teal were seen w i t h t h e i r t a i l s s t i c k -

i n g ou t of t h e water wh i l e t h e r e s t of t h e i r body w a s

submerged, probably s i f t i n g mud f o r food. They were a l so

found f eed ing on t h e marginal vege t t i t ion o f A t r i p l e x

(Sa l tbush ) and g r a s s e s . The Swans too were observed with

t h e i r heads under wa te r , and l i k e t h e Ducks and Tea l

probably s i f t i n g mud. They were ac tua l - ly seen f e e d i n g

I on t h e a l g a , Entermorpha. The Tree-Martins a r r i v e d a t a I

t ime when a cons ide rab le number of i n s e c t s were p r e s e n t

i n t h e a i r . They made d i v i n g f l i g h t s over t h e pond,

probably i n p u r s u i t of t h e s e i n s e c t s . The Nat ive Hens

and Bald Coots febd bo th on land and i n shal low water.

Breeding a c t i v i t i e s commenced with t he a r r i v a l of

t h e Swan p a i r , i n l a t e J u l y . A n e s t w a s cons t ruc ted by

t h e p a i r on an i s l a n d near t h c middle of t h e pond. The

n e s t was made of g r a s s e s and sedges and about one metre

i n diameter . Seven eggs were l a i d and on September 5 t h ,

t h e two Srims had a company of seven cygnets . The Swans

and t h e cygne ts l e f t t he pond and were found on the r i v e r

on October 16th .

Three p a i r s of Tea l had n c s t s cons t ruc ted among t h c

sedges near t h e r i dge . The n e s t m a t e r i a l s were of sedgcs

and g r a s s e s . Each had a c l u t c h s i z c of twelve eggs on

J u l y 5 th . They were hatched by October l o t h , and each

of t h e p a i r had twelve young. They were absen t d u r i n g a

v i s i t i n l a t e October.

I n t h e course of eampling on October 16 th , at reg ion

6 , a p a i r of Black Duclcs a t t r a c t e d m y a t t e n t i o n by t h e i r

unusual calls and flipping over the water. Their be-

haviour suggested a nest in the vicinity and a thorough

search led to the discovery of a very well hidden nest

with ten eggs. It is obvious now that they were trying

to distract me away from their nest. The closer I got

to the nest, the more pronounced were their calls and

flipping. When their distracting behaviour was of no

avail, they flew into the sky and circled above me. The

visit in late October showed all the eggs were hatched.

r\ Three pairs of Plover were beliered to be breeding '\

along the southern edge of the pond. Their eggs were

never observed, obviously well' camouflaged and only one

pair was finally observed with four young. It seems that

Plovers become aggressive during the breeding season. If

a breeding pair felt that intrusion was imminent, they

took off from their nest to #another spot and proceeded

to make distracting calls. If this was ignored, the calls

increased in intensity. If this too failed, the birds

dived at the intruder menancingly.

At the height of the breeding activities in the

pond, a Swamp Harrier was observed to make occasional

visits from the river. As soon as the hawk was sighted,

the Plovers raised their alarm calls and either a pair or

a $lock would take to the air and attack the hawk which

was actually driven back to the river on all occasions.

Meanwhile t h e Teal and t h e i r young h u r r i e d t o t h e edges

of t h e pond t o seek r e fuge i n t h e marginal vege t a t i on .

The P lovers even a t t acked a f l y i n g White-faced

Heron. Although f l o c k s of Ducks, Tea l and G u l l s came and

l e f t t h e pond, they were never a t t a c k e d by the P lovers .

Th i s sugges t s t h a t agg res s ive behaviour i n P lovers w a s

s t imu la t ed by s i g n s t i m u l i c h a r a c t e r i s e d by s i z e , o u t l i n e

and numbers . There were about f i v e Bald Coots and fou r Nat ive

Hens l i v i n g i n among t h e sedges and r e e d s of t h e pond. A

Bald Coot was found runover on t h e road , e a r l y i n t h e year.

A p a i r of Bald Coots commenced breed ing i n l a t e October,

whi le a p a i r o f Nat ive Hens w i t h seven young was observed

a t the same time. These b i r d s a r e q u i t e wary of Man.

Unlike o t h e r b i r d s which seem t o in te rmingle a t l e a s t i n

t h e non-breeding season, t h e Nat ive Hens and Bald Coots

seemed t o be incompatible. They were always found f a r

a p a r t and t h r i c e t he Hen was observed t o chase t h e Coot.

Two n i g h t obse rva t ions were made, one .moon-lit and

one moonless n i g h t , between 8 p.m. and 12 midnight. Not

more . than s i x b i r d s were observed on t h e pond on bo th

occas ions .

Aves of a p a r t of River Derwent.. . .

Ducks, Tea l , G u l l s and P love r s were seen t o l eave

t h e pond towards t h e r i v e r and v i c e ve r sa . These

observations prompted an estimation on the same day as

the sampling days of bird species and abundance on a

part of the river adjacent to the pond. The river part

chosen to study extended from the Brick Kiln near Granton

to just beyond thebridge, leading to Bridgewater. The

estimations began on May 18th, and were made from three

points along the river, namely, ( 1 ) from the bridge,

(2 ) riear the railway station in Granton and (3) from the

brick kiln. The estimations were made at about 5 p.m.

Eastern Standard Time and the weather was also noted.

Weather

Date sky Wind

18-5-67 Overcast - 5-6-67 Sunny, clear sky N.W. moderate

26-6-67 Sunny, patches of cloud N.W. light

3-7-67 Sunny, clear sky S, light

24-7-67 Sunny, patches of cloud N . N . light

14-8-67 Slightly overcast N. W. moderate

5-9-67 Sunny, clear sky N.N. light

26-9-67 Slightly overcast W. strong

16-1 0-67 Sunny, patches of cloud N.W. light

In addition to the Gulls, Teal, Ducks, Swans and

I-Iawks found at Granton Lagoon the following were also

present: -

Fam: Podicipedae "Podiceps poliocephalus (~ard. and

Hoary-headed Grebe selby)

Fam: Phalacrocoracidae *Phalacrocorax carbo i inn.)

Black Cormorant

+Phalacrocox fuscescens (vieill.)

White-breasted Cormorant or

Black-faced I

Fam: Fulicidae *Fulica atra (L.)

Coot

The results of the study is shown graphically on page 63

(Fig. 19). In the case of the Gull, Teal and Ducks,

the population of Grantbn Lagoon is also shown on the

same graph for comparison. Although the abundance of

Gulls tend to show a positive correlation between the

river and the pond, at times they are totally absent on

the river. The Teal and the Ducks showed marked fluctua-

tions in numbers on the river, but a more or less stable

population persisted in the pond. This suggests that

the Teal and Ducks were using the river as temporary

haunts used for feeding and resting. This could be due '

to the exposed nature of the river, where water could be-

come choppy at times.

The Swans which were high in numbers and ~ersistently

showed a gradual decline in numbers. The Coots which

were always found in association with the Swans were

Fig. 19 - Taporal distribution and aburdance of Aves, on a part of River Dement, adjacent t o Cranton Iagoon, 1967.

I I I 1 I I White-breasted -

Cormorant -

Hoary-headed -

Grebe

No. 0 I---.

Chestnut Teal I i I

Si lver C u l l

0

3 r I I

A S 0 / i-f , J -L.-?-J L--l.--- 1 I Month

- River Derwent, t----. Granton Iagoon.

abundant andpcrsistent Iduntil the second last observation.

The Grebe and the White-breasted Cormorant which were few

in numbers were persistent but their numbers fluctuated.

The Teal, Ducks, Swans, Coots and Grebes were always

afloat, either resting, cleaning or feeding. The

Cormorants were always found standing on stumps and rocks

I of the river.

Oversummering of organisms.

The main problem which has to be overcome by the p v ~ n

inhabitants of a temporary is the period without water. f i

Most of the individuals of the habitat have some means

which they employ to survive the drought period and later

re-establish themselves.

The most obvious group to consider are those which

have adult stages that are not exclusively aquatic and

ca; leave the pond when conditions become unfavourable.

The birds and the waterfowl move to more suitable enviro-

ment such as the nearby rivers. These animals seem to

have a life cycle timed so that their aquatic young are

present during the period when the pond contains water.

The young birds grow and leave before the pond dries out.

Within a month of their hatching at Granton Lagoon, the

young of the Swans, Teal and Plovers had disappeared be-

fore there was any sign of the pond drying. While the

Swans and their young moved to the river, the rest, or at

least a portion of the young, are assumed to have grown

sufficiently to fly off.

A group closely linked to the above are some

dipterans. The mosquito larvae was a purely winter

species and probably survives the drought as adults.

Another group comprises of those which generally

spend the dry period as dormant stages in the mud. Earlier

we noted that the fish aestivated in soft mud under water.

Although the fish were aestivating, they may still need

to respire at a reduced rate to survive. A method

adapted from Cole (1932) was devised to measure the dis-

solved oxygen tension of water in mud. The apparatus

used is shown on page 66 (I?ig. 20). It comprised a

sintered glass filter attached to a air-tight cylinder.

The filter was detached and after adding paraffin oil was

retusned to its place. The three clamps, A, B and C were

kept open until the oil commenced dripping out; then

clamps A and C were closed to prevent further escape of

oil. The whole apparatus was then introduced into the

water and the filter was pushed about 2 to3cm. into the

mud. The apparatus was then clamped to a support.

Clamp A was opened, which allowed water in the mud to

diffuse through the filter simultaneously pushing the

paraffin up. The paraffin prevented diffusion of oxygen

from the air into the water in the cylinder. After about

ig.20-Apparatus for extracting Water in Mud t o deternine Dissolved Oxygen i n the water.

Fig.2l3.Fenmle Daphnia carinata with a Ephtppim.

Alimentary Tract

Ephippium

two hours standing, the water level in the cylinder norm-

ally reached the level of water on the outside. Clamp A

was closed and the apparatus was removed. The water was

gently run out into a bottle through outlet C by closing

clamp B and opening clamps A and C. The oxygen tension

in the water sample was determined by Winkler method.

The experiments were conducted at region 6D where the

fishes were found and the results are as follows:-

July 24th 0.40 ppm

September 5th 2.60 ppm

October 16th 4.70 ppm

Although by July 24th, the pond was nearly at its maximum

depth and changed very little thereafter, the oxygen - tension increased with time; increasing from a low. 0.40

to 4.70 ppm in October. Benthic organisms, including

those aestivating, probably could tolerate such a low

oxygen tension as 0.40 ppm or possibly a lower level still.

To determine what organisms were present in dormant

stages in dry mud, water was added to dry mud samples . - collected in March. The samples were enclosed in plastic

boxes with lids, and were kept at constant temperatures

.with aeration. They were examined at intervals and the

results of a particular sample kept at 2 5 O ~ is shown

graphically on page q6 (~ig. 21) . The organisms observed in the water comprised ciliates,

Rotifers, Nematodes, Planarians (~habdocoel), Naupli:i,

Ostracods (~andonini), Daphnia, Macrothrix, Cyclops and

Boeckella.

After a day of submergence, the water was abundant

with ciliates, Paramecium being dominant, and a large

numbcr of nauplii. Their abundance persisted until the

sixth day, after which they dcclined rapidly and disappeared.

The rest of the organisms did not appear until the

fourth day, except for the Planarians which wydobserved

on 62nd day. The Rotifer was relatively low in density

and disappeared on the 50th day and absent thereafter.

The Nematodes were few and were only met occassionally.

The Planarians appeared quite late and were in low numbers.

The Ostracods however, were persistent, but were sparse

for the most part except initially when they were abund-

ant. The few Daphnia which emerged had a very short

duration of less than twenty days. The Flacrothrix were

in high densities until the 34th day after which they de-

clined very rapidly, but vere persistent. The Copepods

exhibited marked fluctuations in numbers with .time.

Cyclopswere persistent, but Boeckella were absent for a

short period from the 18th to 3lst day. Cyclops were

generally more abundant than the Boeckella.

These organisms had some form of dormant stages in

the mud. Apart from the Cladocerans i.e. Daphnia (see

Fig. 21 on page 66) and Macrothrix which have ephippia 5 as an oversummering stage, the dormant structures or

stages of others were not established. Barclay (1 966)

found that Ostracods formed resistant eggs and Copepods

Could remain in mud as encysted late copepeolid. She

also found that adult Ostracods could seek damp places,

cl-ose their vall%es tightly and pass into torpidity. That

protozoans form cysts to tide over adverse periods is

well known.

In collecting ephippia from dry soil by the method

of flo.atation in the laboratory, twice an Amphipod i lo'

emerged from the soil and swam. This suggested that the

animal could survive as an adult in a soil cocoon i.e. a

cavity in the mud with sufficient humidity to maintain

life.

Spirogyra following its peak abundance, commenced

zygospore production in early spring. In Daphnia, which

persisted in Winter and Spring, production of ephippia

started from late winter and continued into spring. A

graph confined to the period in question and the total

population of Da~hnia and that of ephippial Daphnia during

this period is shown on page 71 (Fig. 22).

In the laboratory, a culture of Da~hnia kept at 15%

or room temperature, when left 'to dry, produced ephippia.

Loss of water and resulting increase in osmotic pressure

/7 Fig. 21 - Changes in Densities of Organisms eeneratd when

1 D~J S o i l frcan Granton Iagoon vas submerged i n water -

and kept a t 2 5 ' ~ for 90 days.

Pianaria i Rotif er

- L .-O-.+/---

---I 1.

0 . 20 40 a 60 80 . .

Days Density l e s s than 1 per Lit.

A Density greater than preceding reading.

22. - Changes i n Density of Daphnia carFnsta, Cranton Iagoon, August t o October, 1967.

20 No. Per 103cc.

I Ephippial Population I i

Fig. 23 - Ephippial Production i n a Cul- of Da hnia carineta -3 raised from a s ingle Daphnia and kept a t 1 5 .

Males and Ephippial Females 400 appeared here.

3043 Total

200

100

0

0 -

I I I

A S 0 Month

could have t r i g g e r e d eph ipp ia l formation. An experiment

was devised t o i n v e s t i g a t e t h e probable cause of eph ipp ia l

product ion. A c u l t u r e was r a i s e d from a s i n g l e Daphnia

kep t i n pond w a t e r , which was d i l u t e d a t r e g u l a r i n t e r -

v a l s i n an a t tempt t o reduce d i s so lved s o l u t e s . The

Daphnia reproduced, bu t when t h e osmotic l e v e l f e l l below

0.05% NaC1, t he popula t ion d ied . (See Tolerance Range of

Daphnia t o Osmotic P re s su re , page 85 ) .

I n another experiment, a c u l t u r e was r a i s e d from

t h r e e Daphnia i n pond water wi th p recau t ion t h a t t h e

wate r l e v e l , - h e n c e t h e osniotic p r e s s u r e remained cons t an t .

The c u l t u r e was observed a t r e g u l a r i n t e r v a l s and t h e

counts a r e graphed on page 71 (p ig . 2 3 ) . A t t h e i r peak

abundance, males and eph ipp ia l females were observed i n the

popula t ion . Th i s suggested t h a t e p h i p p i a l p roduc t ion

was a t l e a s t n o t d i r e c t l y r e l a t e d t o d e s i c c a t i o n and i t s

r e s u l t i n g i n c r e a s e i n osmotic p re s su re . Probably,

Daphnia a f t e r producing a number of gene ra t ions by p a r t h e w

ogenes i s automatically goes i n t o sexua l reproduc t ion t o . -

form ephippia . Th i s hypo thes i s i s f u r t h e r r e i n f o r c e d by

f i e l d obse rva t ion of eph ipp ia l Danhnia even though t h e r e

was no s i g n of d r y i n g i n t h e pond. Barclay (1966)

observed t h a t bo th i n temporary and permanent ponds, t h e

eph ipp ia l eggs were produced a u t o l t ~ a t i c a l l y i n summer

months, appa ran t ly r e g a r d l e s s of t h e d u r a t i o n of t h e

a q u a t i c h a b i t a t .

Discussion

Odum (1961) maintained that thermal stratification

was of minor importance in ponds. Georgc (1961) too

concluded from his studies of shallow waters (1 .m. ) that

stratification was not important. Studies maintaining

similar views usually fail to document a lack of stratif-

ication (~riksen, 1966). Even if the generalization is

true, the idea appears not to be well based.

Slight differences in temperature between the sur-

face water and the bottom of the pond wad observed at

Granton Lagoon and on a particular day a microthermocline

0 was rccorded. A temperature difference of 1.5 C was

noted between the surface water and 25 cm. depth. For a

35 cm. depth, Barclay (1966) has recorded 8.5'~ and

Erikscn (1966) has recorded 15.0~~. Eriksen suggcsted

that stratification is a cor~rmon event in many shallow

isolatcd waters of turbid nature and existing in areas

where fair differences in day-night temperatures occur.

He maintained that turbidiky is mainly responsible for

the extreme nature of stratification. Suspended materials

in the water intercept light to produce heat (~nderson,

1958) and if the particles arc concentrated near the

surface, stratification could result following sunrise.

Restriction of light penetration limits photosynthesis.

When this occurrence is superimposed upon a thermally

stratified shallow pond, severe oxygen stratification

may result (~riksen, 1966), and an observation to this

effect was noticed on July 24th. (See page 23 (pig.7)).

Observations of thermal stratification in deep

lakes and their effect on spatial distribution of the

pelagic organisms is well established (~utchinson, 1957).

Although there is a significant amount of documentation

of thermal stratification in shallow waters, their effect

on spatial distribution of organisms remains to be studied.

In studying pH and chlorinity, the notable features

were their variation from one region to another region

of the pond. Similar interregional variations were also

noted in the species diversity and abundance. These

observations suggest thc diverse nature or heterogeneity

of the pond.

Thc use of Protechmeter for measuring dissolved

oxygen tension was discontinued when it Tias found un- * reliable. Onc should bc aware of the limitations of

instruments and thc need to test them periodically for -

correction or reconditioning or replacing the instrument

or cven adopting a new method.

The methods of sampling were quite satisfactory,

although they had their pros and cons. The sweep net / method enabled any desired part of the pond to be sampled

and allowed stratified sampling. Furthermore, it was

an economical method. It had its disadvantages too. It

is quite impossible to capture by the sweep method all,

or a definite proportion of the organisdin a given

volume. The capture depends largely upon the reaction

of the organisms especially the motile ones to various

stimuli. These stimuli will vary in predominance or

complexity at different times. Many physical factors

are involved which may influence the rate of response or

behaviour and consequently affect the size of the popula-

tion sampled.

Temperature is a very important factor since it

affects metabolic rate and hence the speed of escape re-

action. Mosquito larvae near the water surface were

observed to swim to the bottom as soon as the water was

disturbed and the rate of the reaction would undoubtedly

be affected by temperature. Under these variable condi-

tions, a'uniform method used by the observer such as the

speed of the sweep, would not give a representative

sample of the population.

Changes in light intensities such as caused by the

falling of observers shadow could affect escape reaction.

The solution could be a long handle attached to the net,

but there is a limit to the length, and the shadow of the

net is not eliminated.

A tow net is not practical because of the shallowness

and the presence of dense hydrophytes and filamentous

algae which would clog the net. A more satisfactoy

method would be the use of a cylinder and a pump. The

cylinder which is opened at both ends is thrown into the

pond to fall upright. It is then pushed into the ground

and a pump is used to extract the entrapped sample. This

method could prove laborious. : . The mud sampling technique was found satisfactory

and a very economical one too.

A study of population dynamics entails the estima-

tion of the densities of the populations. Ideally, an

absolute count of the organisms would be desirable. Is -.

absolute count possible and is it necessary? With some

species such as the birds of the pond absolute count is

possible, but it is quite impossible with many species

such as the aquatic communities of Granton Lagoon be-

cause of their species diversity and abundance. It is

not necessary for my purpose because I am concerned with . . . -

the fluctuations in numbers and this can be determined

from samples drawn from the populations. It is suffic-

ient to know in what ratio one population exceeds another,

without knowing what the actual size of the population is.

Estimation of population size in this manner gives relative

densities rather than absolute densities.

Are the samples taken, representative of the

popUions? This question is not easily answered for it

depends on the size of the populations, the duration of

investigation and the experience of thc observer. But

one could approach a satisfactory estimation of densities

by drawing large samples from different parts of the

habitat in which the populations exist. The size and

the number of subsampling and the subsequent counting are

all governed by the time available. In an attempt to

obtain reliable estimates, the pond was divided into 8

regions and sub-samples from 6 to 12 were taken from each

region in a semi-random manner. The final results

showed that the densities varied from region to region

throughout the period of investigation. This we saw was

correlated to the interregional variations and trends in

pH and chlorinity. It is a possibility that the inter-

regional variations in densities could be an art.ef.act

but it is very much doubted.

Sampling was at semi-random instead of being random.

Mosquito larvae were usually confined to the margins of

the pond where shade was provided by the vegetation.

/ Collemb lids were initially found in clumps around faeces

and under windy conditions were found dispersed. Dauhnia

were nearly always found in aggregations indicating that

they were gregarious. These observations suggested a

semi-random sampling in order to obtain representative

samples of the populations. The necessity to select some

places was demonstrated on one occasion when sub-sampling

at region 6D. On completion of sub-sampling at this

region, there were only a few Daphnia in the sample drawn.

But later it was found that there was a extremely large

aggregation of Daphnia at one end of the region which

suggested that thc sample drawn earlier was not truly

representative.

Since my primary interest was in the animals of the

pond, only these were studied quantitatively. The algae,

protozoans, rotifers and nematodes were only studied

qualitatively. The latter, if studied quantitatively

could itself q%b~ a project comparable to the former. ~.

It is difficult to tell what the effect of rain was

on the population dynamics. Sampling results following

rainfal.1~ on two occasions i.e., April 26th and July 3rd

indicate that there were little or no changes in the

population densities. The sampling technique could have

failed to detect the changes, if there were any.

Organisms could have takenshelter following the rain-

falls. The main effect observed of the first rainfall

was to increase the chlorinity significantly, while the

second rainfall led to slight dilution.

The prominent features of the population studies were

dominance and succeskon. As was stated earlier, G Ls

different species would undoubtedly .have different

physical, chemical and biological requirements and it could

be that a particular species predominates at a particular

season because the prevailing conditions are favourable.

In this study, I concluded that of the factors studied,

temperature and depth of water were more important than

any others as controlling factors. Predation or select-

ive grazing by higher organismsand parasitism may have

important influence on succession. The latter ,statement

is quite similar to the concept of food web. Although

organisms, birds in particular, were observed feeding, no

further observation was made regarding predator-prey or

consumer-food relationship apart from observing the Swan

feeding on Enteromorpha. The nature of the food web

undoubtedly would hqve a large effect on dominance and

succession.

Continued observation often reveals factors which

are of major importance, for example, the influence of

light in temperate lands in determining the time of the

start of the spring increase of plankton, even though this

may not be a universal feature (~und, 1965). The

1 organisms I studied seem to be geard to seasons, but one LC

2

year's observation is always open to the possibility that

the events observedwere abnormal. Prolonged observation

would make it possible to separate the usual from the

unusual. In turn, the unusual happening when recognized

as such, could supply valuable clues to factors determin-

ing the usual situation.

Since the pond was progressively covered with water,

different parts of the pond had slightly different dates

of beginnings and ends in their succession and dominance.

This was quite noticable for the higher algae in the

field. Entcron~orpha which began in region 6, slowly .

spread to the rest of the pond. Spiromra on the other

hand started from regions 1 and 2 and spread to the rest

of the pond. Nitella which began along the southern

border '4 spread'& to the rest of the pond. This 2 2 suggests centres of growth from which the algae radiate,

but this may not necessarily be so, for earlier establish-

ment in certain parts of the pond could be due to suitable

local conditions.

The investigation was confined to the study of

pelagic and benthic organisms of the'open water. Organisms

dwelling among the marginal vegetation and in their roots

were not investigated. These microhabitats may have

slightly different species diversity and abundance.

Special techniques are needed to study these micro-

habitats.

In the list of species given on pap41-48'tkr: absence of

7 7 molluscs and echinoderms is notable. While all knorvn '

echinoderms are marine (~illee, 1967), members of the

mollusc are lcnown to occur in ponds. According to

M r . Gould, a former owner of the farm, a mollusc was

present, but disappeared before he left in 1961. This

could have been due to the increase in severity of the

summer droughts leading to the mollusc becoming extinct

in this locality. It could also be due to a shortage of

calcium needed for shell construction. The latter

reason will be discussed further in the section on tempor-

ary and permanent ponds. g,O.c m o / l u r r are P a c t cqalk,/973.

The breeding performances of the ruaterfowl were

highly successful. They all had high cl.utch sizes comp-

ared to the average figures reported by Frith (1966) for

Canberra.

Granton Lagoon Canberrn

Teal 12 8.9

Black Duclcs 10 9.1

Black Swans 7 5.5

Furthermore, no mortality in the eggs or young rias observed.

Granton Lagoon is a sanctuary, especially created

for riaterfowl. In the introduction, it was mentioned tht

the trees and stumps which serve as nesting sites for the

birds were reir~oved by man. This year on April 20th, a

stand of reeds along the northern border of the pond rvas

burn t down. Nat ive Hens and Bald Coots a r e known t o

dwel l among the r eeds . Although a t t h e moment, t h e r e i s

no s e r i o u s danger t o t h e b i r d s i n t h e sanc tuary , a sanctu-

a r y wi thout proper management may f a i l a s a s anc tua ry .

O n my f i r s t v i s i t t o t h e pond, a Blaclc Duck xias

found a l i v e w i t h a deep gash i n t h e stomach. T h i s could

have been caused by t h e overhead e l e c t r i c wi res o r fence

wi re s a s t h e b i r d came t o land . A Bald Coot was a l s o

found runover on t h e road. A l l t h e s e obse rva t ions

suggest t h a t when c r c a t i n g s a n c t u a r i e s , t h e choice o f

land should be made a f t e r c a r e f u l l y cons ide r ing t h e prob-

lem of i n t e r f e r e n c e of human a s we l l a s h i s technology.

I11 Laboratory S tud ie s

Th i s s e c t i o n comprises r e p o r t s on some s t u d i e s

c a r r i e d ou t on Daphnia c a r i n a t a . The s t u d i e s i n v e s t i g a t d i

1 ) Cyclomorphosis of Daphnia

2) f i e Osmotic t o l e r a n c e rangc of Daphnia

3) T i c r e s i s t a n c e of eph ipp ia t o d e s i c c a t i o n and

4) Some f a c t o r s a f f e c t i n g ha t ch ing of cphippia .

Cyclomorphosis of Daphnia

Cyclomorphosis - i s def ined a s t h e seasona l changes

of form i n a organism (welch, 1935, Hutchinson, 1967).

T h i s phenomenon i s q u i t e common i n planlrtonic organisms

v~h ich inc ludes Daphnia. I n some s p e c i e s , t h e summer and

win te r forms of t h e sane s p e c i e s could be markedly

d i f f e r e n t t o t he e x t e n t t h a t they could be mistaken f o r

d i f f e r e n t spec i e s .

However, no s i g n i f i c a n t changes i n t he morphology

of Daohnia of Granton Lagoon r</ d e t e c t e d du r ing t h e

p e r i o d of i n v e s t i g a t i o n .

The Osmotic Tole rance - Range of Daohnia

T h i r t y Daphnia were p l aced in each of n i n e p e t r i

d i s h e s con ta in ing va r ious s a l i n e s o l u t i o n s . The Daphnia

wcre observed at i n t e r v a l s and the time noted f o r 50%

and 100% m o r t a l i t y . #hen a Daohnia appeared t o be dead

i t was withdrawn and placed i n some pond water . I f i t

recovered wi th in a minute, i t was r e tu rned t o i t s o r i g i n a l

container, otherwise it was recorded as dead. Filtered

pond water (FP) and deionized water were used as controls.

The experiment was duplicated and the combined results

shown below. The figures for mortality are in hours.

A graph of the results is shown on page 85 (~i~.24).

It can beseen that the tolerance limit at 50% mortality

lies between 1% and 5% of salinity. This observation

correlates well with field studies where the Daphnia

existed in a medium with a range varying from 1.30% to

5.73% of salinity, the average being 2.69%. Such a

relatively wide tolerance indicates the adaptibility of

the organism to an environment in which fluctuations of

salinity could be wide and common.

- Salinity

%

Resistance of Ephippia to Desiccation.

Fifty ephippia were enclosed in a perforated tube

together with a piece of cobalt thiocyanate paper to

measure relative humidity. The tube was introduced into

a larger container with a desiccating agent such as sodium

hydroxide or calcium chloride and then sealed off with wax

1

23.00 7.08

23.00

50% mortality

1 O& mortality

5

23.00

68.00'68.00

-

'68.00

7

2.33

3.92

8

0.78

2.87

10

0.50

1.00

15

0.08

0.40

20

-

0.20

Fig . 2.!, -Tolerance Range of Daphnia carinata to Osmotic Pressure.

Hrs.

Fig. 25 -

% Hatched

Resistance to Desiccation of Ephippia of Daphnii

r I-- 1-- I

20 1.- 1 I

0 4 8 12 16 Days

and stored at 25'~. . After a 'number of days, the

ephippia and the paper were removed. The paper was im-

mediately immersed in paraffin and its R.H. estimated by

comparison with standard coloured discs of lcnown R.H.

The ephippia were tested for viability and hatching by

submerging in water 'at 1 5 O ~ and observing the number of

daphnids produced within 20 days. After this period,

the expefiment was terminated and a sample of ten ephippia

was talien and dissected to determine the number of un-

hatched eggs. The procedure to determine the percentage

hatched can be exemplified' as follows:-

1) No. of daphnids observed within 20 days, 60

2 ) " " unhatched eggs observed in ten

ephippia, 4

3) From 2, no. of unhatched eggs expected

in fifty ephippia, 20

4 ) Hence, initial total no. of viable eggs, 80

, . therefore % hatched 100 = 75% 80

(~ach ephippium encloses two eggs and fifty ephippia

will have 100 eggs. Hence the number. of inviable eggs

is estimated to be twenty.)

The experiment was in replicates of four. The

period of desiccation varied from 0 to 16 days. Except

for zero days, the rest had a R.H of approximately 10%.

87

The results are tabled below and graphed on page 85 ( ~ i ~ . 2 5 ) .

The graph shows that there is a fall of about 20%

after a day's desiccation, and further prolongation of

the desiccating period of up to eight days has no effect

i.e. one day or eight, days of desiccation have the same

reduction in the percentage hatched. But when the

desiccating period was extended to sixteen days, there was

another drop of nearly 20% in percentage hatched.

Although there is a reduction inpercentage hatch-

ing with time, it also indicates that the ephippium is

quite resistant to prolonged desiccation and can withstand

an extreme environment with about 10% R.H. Treatment

without desiccation had an average percentage hatching of

70.7 while treatments with sixteen days desiccation had

32.3$, a relatively high percentage after such a severe

treatment. The extreme resistance of the ephippium in-

dicates its adaptation to possible severity in.'its natural

16

46.43

42.31

3.85

36.78

32.34

Days of Desiccation

Hatched i

ii

! iii

iv

Average % hatched

1

48.53

63.24

58.82

38.46

52.26

0

55.00

75.00

89.25

63.24

70.62

8

50.00

92.42

20.63

29.58

48.16

2

43.04

46.24

58.33

38.46

46.64

4

72.92

54.55

33.73

40.68

51.47

environment w i t h r e s p e c t t o humidity.

. . Examination of some f a c t o r s i n f luenc ing hatch in^: of Ephm-.

An experiment was conducted t o i n v e s t i g a t e some

p o s s i b l e f a c t o r s t h a t could i n f l u e n c e t h e ha tch ing of

eph ipp ia of Daphnia c a r i n a t a . The f i r s t f a c t o r e s t a b l i s h -

ed was, t h a t submergence was e s s e n t i a l . Ephippia l e f t

f l o a t i n g i n water f a i l c d t o ha t ch . ( ~ ~ h i ~ ~ i a normally

f l o a t i n water.) I n one experiment, where dry s o i l was

submerged i n wa tc r , a l l t h e f l o a t i n g ephipp ia were removed, 7- bu t daphnid d i d emerge a f t e r f o u r days. This suggested

t h a t t h e s e daphnids could only have come from ephippia

t rapped i n t h e s o i l .

To achieve submergence was n o t simple w i th ephippia ,

which a r c small . Furthermore, i t was d e s i r e d t h a t t h e

ephipp ia should n o t be unduly confined. The problem was

overcome by t h e u s e of smal l p l a s t i c tubes of 3.0 cm.

long and 1.j cm. i n diameter . One end w a s open, whi le

t h e o t h e r was covered w i t h a f i n e nylon mesh. A smal l

p i ece of g l a s s t ub ing was a t t a c h e d t o t h e s i d e of t h e

tube a s a weight t o p rcven t f l o a t i n g . The cphipp ia were

in t roduced i n t o t h e p l a s t i c tube and a drop of wate r added

t o hold t he ephipp ia a g a i n s t t h e s i d e of t h e tube. The

tube was thcn submerged wi th t h e open end f i rs t e n t e r i n g

t h e wate r . The water c o n t a i n e r was a 250 cc . beaker

provided w i t h a p l a s t i c p e t r i d i s h as a l i d .

Fifty ephippia were used in each treatment. The

factors examined were temperature, aeration, photophase

0 and soil. Temperatures considered were 5 , lo0, 15O, 2 9

and 30°c, with aeration or no aeration, with 0 or 12 hours

photophase and with soil or no soil. The soil came from

Granton Lagoon and the amount added where necessary was

about a gram for each treatment. The experiments were

duplicated.

At 5O, lo0 and 30'~ there was no hatching, while.at

25Oc the hatching was nonsignificant and at 15'~ hatching

was significant. The table below shows the results of

the experiment at 15Oc. The procedure for determining

percentage hatched is similar to that explained earlier

on page 86.

An analysis of variance of the above data shows that

aeration was the only factor significant at the 5% level

of probability. The other factors were non-significant.

This is contrary to what was expected. The table above

indicates that twelve hours photophase treatment h P+c higher percentage hatched than 0 hours photophase, no

aeration higher than aeration and finally soil treatment

higher than those without soil. It was expected that

soil factor would be the most significant factor. Treat-

ments with soil h e a total percentage hatched of / 288.87 in comparison to 173.76 for treatments without soil.

Moreover, determination of dissolwed oxygen in treatment

with and without aeration showed little difference be-

tween them - aeration treatment had a oxygen tension of 9.50ppm. while the non-aeration had a comparable 9.20 pp.

- which was undoubtedly due to the constant temperature of

15'~.

All the experiments reported below had a twelve

hours photophase, no aeration, kept at 15'~ and were term-

inated after twenty days. The following were the observ-

ations made in these experiments.

To verify the significance of oxygen, experiments

were set up in which nitrogel; gas was bubbled through the

solution for varying times of 0 to 10 minutes. These

were then sealed with little'or no air present together

with fifty ephippia in each case. No hatching was

observed.

The pH f a c t o r was examined too. I n t rea tment

wi thout s o i l , t h e pH range was 5.02 t o 5.60, whi le t hose

w i th s o i l had a range of 7.51 t o 9.10. Buffered so lu-

t i o n s w i t h a range of 5.65 t o 9.50 were prepared and

t h e i r e f f e c t on ha t ch ing examined. No ha t ch ing was

observed.

The s o i l was cons idered nex t . S o i l hea ted over a

nalced f lame f o r two hours o r heated i n an oven f o r two

days w i th h a l f a day i n t e r r u p t i o n gave a higher percentage

ha t ch ing i n a s h o r t e r time than d i d t rea tment with un-

heated s o i l .

Heated s o i l - 6.5 days f o r 50% hatchea

Unheated s o i l - 11.5 " " I I t

The r e s u l t s suggested t h a t some inorganic mat te r i n t h e

s o i l o r t h e r e s u l t a n t p roduc t of t he hea-lbed soil . had an

important i n f l u e n c e on t h e r a t e of ha tch ing . %e oven

t rea tment was presumed t o have des t royed a l l organic matter.

I n t e r e s t i n g t o no te was t h e experiment i n which

f i l t e r e d pond water was used , b u t eph ipp ia f a i l e d t o hatch

i n them.

It may be concluded t h a t of t he f a c t o r s examined

a f f e c t i n g t h e ha t ch ing of eph ipp ia submerkence, temperature

and s o i l were found t o be more important than a e r a t i o n and

photophase.

IV A Brief Ecologi~al Study of Calvert's Lagoon

A Brackishwater Permanent Pond. Introduction

The aims of this investigation vere: 1) to make a

qualitative study of the organisms inhabiting the pond

2) to examine what .range of physiochemical. conditions the

organism encounter and finally, 3) to compare the pond

with Granton Lagoon, a temporary pond.

The pond was visited monthly, from Nay to October,

1967, inclusive.

General Dcscription.

The pond is also known as Collin's Spring. It is

located on a farm in South Arm, 12.5 miles south-east of

Hobart. Its outline resembles that of a heart, has an

area of about 0.48 scl. kilometers (117.6 acres) including

the shore and its maximum width is about 890.0 metres

along the east-west direction. It has a distinct shore

which is largely sandy except at the mid-northern part

where i-t is roclcy. Thc immediate farmland around the

pond is covered with grasses, rushes, shrubs and eucalypts.

Being located in a depressed basin, water from the surround-

ing area would undoubtedly drain in. Along the southern

border is a sandy mound which separates it from the sea.

It lies in an area with a annual rainfall of approx-

imately 22 inches. The most prevalent wind encountered

was north-westerly and at times, southerly or easterly.

Vegetation.

The pond was characterised by a dense vegetation

of'i%oted hydrophytes over the entire basin, these

greatly contributing to the clarity and general stillness

of the water. The 2 main hydrophytes were :-

Scirpus '2nodosus Rottb. - a sedge. My- hylum propinquum A.Cunn. - a dicotyledon.

The water was extremely clear, and when examined micro-

scopically had only a few diatdms, ciliates and Vorticella.

Physiochemical Studies.

Weather on Sampling Days

Date sky Winds

9-5-67 Sunny Moderate N.W.

Cloudy

Sunny Light S.

26.8.67 Sunny Moderate E.

9-9-67 Slightly overcast - 7.10.67 Sunny Moderate N.W.

Temperature.

Temperatures were recorded at 1.00 p.m., Eastern

Standard Time at a fixed position. Temperature taken - near the bottom was always similar to that observed 2 cm.

below the water surface. This could be due to the

shallowness and extreme clarity of the water which allowed

light to penetrate to the bottom without significant

interception by suspended particles or absorption by

the water.

The air and water temperatures are graphed on page

9.6 ( ~ i ~ . 26) and they show a close correlation.

pH and Chlorinity.

These factors were measured in the laboratory from

samples collected in the field . Only one sample was

collected on each occasion from a fixed location.

The results are shown graphically on page 97 ( ~ i ~ s .

27 and 28). The water was always alkalino with a range

which fell between pH 8 and 9.

The chlorinity ranged from 5.47 to 8.19%, the

average being 6.16%. The maximum of 8.19% occurred in

June which could have been due to drainage of water, rich

in chlorindes, into the pond. The relatively high range

of chlorinity could be due to its closeness to the sea

from which sea-water could seep in through the ground and

spray due to wave actions could also be blown into the

pond by wind.

#

Chemical Analysis.

A water sample collected on November 12th, was

analysed and the results are as follows:-

4500 ppm. 150 " 71 " 0.6G

6200 "

Total dissolved organic solutes 1620 ppm.

inorganic " 10870 " T.D.S. 12490 "

Biolopical Observations.

Water and mud samples were collected along the

margin of the pond. The species present in the samples

were recorded. The table below shows the species en-

countered and their temporal distribution.

Month M J J A S 0

Mytolocypirs tasrnanica + + + + + t

(~stracod)

Cyclops *. + + - - - - , BQdcella triarticiilata - - + + + +

Collembilid - - - - - +

Lestidae + + + + + t

Notonectidae + + + + + t

Corixidae + + + + + t

Limnophilidae + + + + + +

Chironomons *. + + + + + +

Chironomid sp . + + + + + +

Hydrarachna s. - - - + + + (~ite . )

Coxiella badgerensis + + + + + + (~astro~od)

+ or - indicates presence or absence respectively.

Fig. 26 - Graph of Tempenatwe against Time, Calve& Iegoon, 1967.

I I I I I

-

12 - -

O c

8 -

4 1 M i J , 0 Month J I A , S , O ' 0 Air Temp. morded a t &m. abwe water surface. v WaterTemp. * " 2cm. below " I ) .

Pig. 27 - Graph of against Time, ~ a l v e r t b Iagoon, 1967

Month

Fig. 28 - Graph of Chlorinity against Time, ~alvert ' s Iagoon, 1967. 7- 7-

Month

The table indicates that Cyclops, Boeckella,

Collembilid and Hydrarachna were seasonal, while the rest

were persistent. Cyclops was present only in early

winter. Boeckella was absent in early winter, but was

present thereafter. ~ollembi/lids were noted in the last

observation. Hydrarachna was seen in the last three

sampling days. The persistent species were relatively

abundant most of the time.

The bird species and abundance was also noted. The

results are tabled below.

Month M J J A S 0

Grebes 8 - - 250 450 500

Plovers 4 - - 3 - 4

Gulls

Native Hen

Shoveler

Chestnut Teal

Black Duck

Musk Duck

Swamp Harrier

Tree Martin - - - - - 4

- indicates absence; figures represent absolute numbers.

Most of the birds have been met earlier except for

Musk ~ u c k , Biziura lobata haw). The first point to

note in the table is the lack of birds in the June and

July observation. The main waterfowl of the pond was

the Hoary-headed Grebe and to a lesser extent the Teal and

the Black Ducks.

The pond was used as a feeding, cleaning and resting

ground. The late arrival of the Tree-Martins coincided

with a time when there were considerable number of insects

in the air. /

Trout was once introduced into the pond, but having

thrived once, seems to have disappeared for the last two

years. The increase in severity of the summer drought

and temperature are thought to have caused their ' ? / ' .

I

disappearance.

The Lestidae (~amsel-fly nymph) had a gut with a

distinct green posterior end which was characteristic of

all the nymphs observed. The green content comprised

largely of encysted cells with chloroplast and at times

Gregarinida were present. lihether these organisms were

symbio.tic or parasitic or merely accumulation of non-

digestable algae waiting to be passed out, is not known.

A portion of the snail po@ulation was always found

infected with redia, cercaria and metacercaria oS probably

three different species belonging to the digenetic

/ trematodes. Their ultimate hosts is believed to be the r

birds. The life-cycle of a bird trematode as depicted

by Styczynska-Jurewicz (1966) is on page 101 (pig. 29).

The component links of the cycle are present in Calvert's

Lagoon and a similar cycle is possible.

A Comparison between Calvert's and Granton Lagoon.

A comparative study of the two ponds could best be

achieved by tabulation as shbtrn on page 102. Certain

points in the table will be discussed below.

Diatoms require silica for the construction of their

fsstules (~ewin, 1962). Granton Lagoon with a silica

content of 3.0 ppm. had diatoms which exhibited dominance

and succession. Calvert's Lagoon had diatoms, but these

were relatively sparse which could be attributed to the

low silicacontent of 0.6 ppm.

The absence of molluscs and the low calcium content,

28 ppm., of Granton Lagoon are in contrast to the presence

of molluscs and the high calcium content, 71.0 ppm. of

Calvert's Lagoon. Calcium is required in shell construc-

tion of mollusc. According to Smith (1966), a number / of mollusc are restricted to hard water because of in- / sufficient calcium to harden the shells in soft water.

(~ard water contains 53 ppm. of calcium or more and soft

water contains 50 ppm. or less.)

FQ. 29 -The l i f e cycle of a bird trematode, Plagiorchis elemns. Drawing compiled a f ter StyczynshJurwicz (1961).

1. Size (Area)

2. Shore

3. Outlet

4. Hydrophyte

5. Water

6. Water Temp.

7. pH range

8. Chlorinity

range

9. Silica

Calcium

10.Algae

102

Calvert's Lagoon Granton Lagoon

(permanent pond) (~emporary pond)

Large, about Small

12 x Granton Lagoon

Present Absent

Abaent Present

Two dominant spp., One seasonal sp.

which are permanent

Quite clear Turbid

Same at all depth Slight variatim

with depth

8.15 to 8.88 7.36 to 9.08

5.47 to 8.19% 0.61 to 3.47%

0.6 ppm.

71.0 ppm.

Sparse, chiefly

Diatoms

1 1 .Animals Mostly persistent

Daphnia Absent

Lestidae Abundant

3.0 ppm.

28.0 ppm.

Abundant,

many spp., in-

cluding Diatans

Mostly seasonal

Abundant

Sparse

Mollusc 9 Absent

Grebes Present Absent

V Comparison of the Growth Rate of an amphipod,

Austrochiltonia australis, in Granton and Calvert's Lagoon.

In the samples drawn on July at Granton Lagoon, it

was noticed that the amphipods were larger than those

observed in previous samples. It was decided then to

study the growth rate of the animal by observing their

change in length with time. The length measured extended

from the anterior tip of the head to the end of the telson

of the animal. Thirty large amphipods were chosen at

random for measurement. The large ones were selected be-

cause it was only in them that'the changes could be seen

and furthermore the choice avoids including immature in-

dividuals. Also, the amp2itude of the same species from

Calvert's Lagoon was studied to allow a'comparison between

the two ponds.

The results of this investigation are shown graph-

ically on page 104 (Fig. 30). The changes in length were

examined in relation to temperature changes. For Granton

Lagoon, the average monthly temperature of New Norfolk was

used and for Calvert's Lagoon, the average monthly temper-

ature of Hobart Airport was used. Temperatures recorded

on sampling days were not used because the animal lives

longer than a day and it is thus more reasonable to use

the average monthly temperature.

F i g . 30 - Grovth Rate of Austrochlltonia australis, 1967.

Granton Lagoon T

Month I indlaites' * I .96 x Standard 6Aor

Mean 0

Standard Granton Lagoon Month Temp. C Length, $ Error, S:

July 5.9 6.25 mm. 0.37

August 7.3 7.10 0.23

Sept. 9.1 8.00 0.35

11 9.1 * 8.10 0.27

Oct. 10i9 -8.58 0.30

Calvert ' s Lagoon .

July 7.8 4.33 0.24

~u&st 8.5 5.50 0.36

Sept. 10.0 5.75 0.27

Oct. 12.4 6.00 0.21

The data were analysed to test the significance of the

regression both by analysis of variance and by,(correlatioe

coefficient of the mean length and temperature.

at the 546 level of probability and there is a high correla-

Granton Lagoon Calvert ' s Lagoan

tion coefficient between mean length and temperature.

The graph on gage104 also indicates that the amphipod

of Granton Lagoon, a temporary pond, was always longer than

0.5) Pd .01

+0.80 (P 2 .05)

Analysis of Variance

Correlation Coef.

that of Calvert's Lagoon, a permanent pond.

In both ponds, regression was significant at least,

.Ol>Pb .001

+0.98 (PC .001)

Discussion.

Since temperature and length are directly related,

temperature was therefore a possible factor influencing

length in both ponds.

The reasons for the greater length of the amphipods

in the temporary pond than in the permanent pond are as

follows:

(1) It could be due to a difference in the trophic condi-

tions of the pond. Granton Lagoon was always turbid

which could mean an abundance of food particles unlike

Calvert's Lagoon which always had an extremely clear water.

(2) Since most organisms were persistant in the permanent

pond, continuous.predation could have been a selective

force resulting in smaller individuals. Furthermore, pm-

longed selection could have led to sub-speciation, the

new sub-species being characterized by small size.

In correlating temperature with length, the mean

temperature of the month was compared with the mean length

of the same month. It could be more reasonable to compare

the mean temperature of the preceding month to the mean

length of the present month. Such a consideration was

found to give quite similar results to the one adopted

VI Growth Rate of a calanoid, -11% triarticulatq . . . . . . . . . . . . . . . . .

in Granton and Calvert's Lapoon.

A study similar to that of the preceding amphipod

study, was simultaneously conducted on a calanoid,

Boeckella triarticulata. The sedwere differentiated, J

I- the length of the cephalothrax was measured and the clutch

size of ovigerous female was estimated. Males and / ' ovigerous females, thirty each, were taken randomly and

examined on each occasion. The results are tabled below

and graphed on page 108 ( ~ i ~ . 31) . The mean monthly

temperature of New Norfolk and Hobart Airport are included

in the table for Granton and Calvert's Lagoon respectively

Granton Lagoon

Month em^.^^

July 5.9

August 7.3

Sept. 9. 1

Sept. 9.1

Oct. 10.9

Calvert's Lagoon

July 7.8

A U ~ . 8.5

iept. 10.0

oct. 12.4

forcfandq stand for mean cephalothorax length in 4 . Sx = Standard error.

- 8 - x , Sx

- 9 - x , Sx

590

633

593

587

564

694

705

665

637

609

Eggs . . . . X s j;

6

8

13

12

l o

13

7

24

10

8

74.0

80.6

44.1

35.2

24.7

12.6

5.4

2.9

2.7

2.8

d ) ?

590

515

5 24

469

532

5 88

5 80

557

Eggs - 6

1 2

9

10

1

1 1

8

7

36.0

62.0

57.0

17.0

2.8

3.8

3.1

0.8

A test of significance of regression and correlation

coefficient of mean length and temperature gave the

following results:-

Granton Lagoon

l~nalysis of Variance

Correlation ~oef.

Calvertts Lagoon . -

Analysis of Variance

correlation Coef.

.207 p>.10 I Non-Sig. Non. Sig.

-0.60

( p 7 .lo)

Generally there is a good inverse correlation be-

tween mean length and temperature. This is also true for

clutch size and temperature. Although Granton Lagoon in

two cases shows a regression significant at 5% probability

level, Calvertts Lagoon in all three cases is non-signific- -

ant at the 5% probability level. The latter result could

be due to the small nulnber of observations.

From the graph on page108 it may be concluded that:

1) The mean cephalothorax length and the mean clutch size

of the calanoid vary with time of the year in both ponds

and 2) On the whole, the length and the clutch size at

any one time is greater in the temporary pond than in the

permanent pond.

Discussion.

Temperature could have influenced the cephalothorax

length of thi calanoid in both ponds. McLaren (1965)

established a relationship between temperature and body

size, which is related to the length of the cephalothorax,

in Pseudocalanus.

The reasons for the greater length of the calanoids

in the temporary pond than in the permanent pond are

similar to those given for amphipod on page 106.

The triphic conditions in the temporary pond could be

more favourable than in the permanent pond. Granton

Lagoon was always turbid unlike' the clear waters of

Calvert's.Lagoon. The particles which impart turbidity

could be an important food source.

In permanent waters, there could be a selective

factor, resulting in small individuals. Most of the

species of the permanent pond b'eing persistent, the larger

calanoids could iiave been selectively preyed on.

The observed dissimilarity could be due to genetic

differences between the populations of the two ponds.

Price ole 1966) showed the presence of marked genetic

variation in Cyclops vernalis. Tonolli ole 1966)

demonstrated phenotypic variation in ~bxodiaptomus

laciniatus that may have a genetic base. Cole (1966) who

studied calanoids of temporary ponds observed that the

calanoids were exceptionally large. He further observed that

the body size of a particular species may vary from pond to

pond.

In addition to large size, the ovigerousfemale Boeckella

from the temporary pond generally carried more eggs than the

Boeckella of the permanent pond. This could simply be a

function of size, arising from favourable trophic conditions.

On the other hand, genetic selection for large size may havc

occurred because of the valuable increases in clutch size

which follows large size. The latter hypothesis was proposed

by Ravera and Tonolli ole, 1966) who studied diaptomid

in l*es subj;ct to outflow. In thirty-two popu-

lations of Arctodia~tomus bacillifer and in fourteen popula-

tions of Acanthodiaptomus denticornis, they found a positive

correlation between body size, clutch size, and the rate of

water exchange for each lake. They suggested that environ-

mental selection had favoured larger females and consequently

more eggs, thus compensating for loss via out-flow. This

explanation could be applicable to Granton Lagoon for it has

an outlet which could drain the lagoon into the adjacent

river.

Finally, Cole (1966) has suggested that large clutches

in temporary ponds could be an adaptation for life in ephem-

eral habitats where the copepods persist through the dry

periods-,as resting eggs with a possible high mortality in

the eggs.

VII General Discussion of the Two Ponds.

The ponds are small in area compared to lakes.

Water movements were 'minimal and it could be due to the

presence of dense hydrophytes which would restrict water

movements. Furthermore, the ponds were protected from

winds by the elevated surrounding land and forests.

Because of the shallow depth, the pond waters tended

to follow the temperatures of the atmosphere. But under

certain conditions, such as continuous calmness, the water

may become thermally stratified. Plant growth could

reduce any mechanical mixing of the water by wind and help

to establish thermoclines. Turbidity could also govern

thermal stratification. A microthermocline was observed

only in the temporary pond, but was never found in the

permanent pond and this could be due to their difference

in turbidity, the temporary pond was always turbid while

the other was always clear.

Despite the turbidity of the temporary pond, light

was able to reach the bottom of both ponds as evidenced by

the luxuriant growth of hydrophytes in them.

Although the fauna of both ponds were quite similar,

the flora differed strikingly. They had different species

of hydrophytes and the temporary pond was rich in flagell-

ates, blue-green algae, diatoms and Chlorophyceae, unlike

the permanent pond which had scant diatoms.

To establish annual flora and fauna variations

needs long period of observation; nevertheless the obsem-

ation of Wesenberg-Lund (welch, 1935) is noteworthy. He

concluded that nowhere do the variations in the composition

of the fauna seem to be so great from year to year as in

ponds. The necessity for long term observation was

stressed earlier, for a year's observation is open to the

possibility that the events observed were abnormal.

Stout (1964) and Barclay (1966) observed that the

temporary pond showecl a lack of faunal diversity in

comparison with a permanent one. They have suggested that

the two factors contributing to this condition are a lack

of habitat diversity and the period without water. My

observations are contrary to those of Stout and Barclay

who based their conclusions on studies of relatively small

ponds. The temporary pond I studied had both a greater

fauna and algae diversity than the permanent one. Seasonal

succession in a relatively large temporary pond like the

Granton Lagoon, allowed retention of numerous species

which otherwise could have been displaced in a permanent

pond where the organisms tend to be persistent and probably

create severe interspecific competition.

The basic difference between the two ponds was, one

was temporary and the other was a permanent pond. The

organisms of the temporary pond face the problem of summer

drought and as such has to evolve means of oversummering.

Unlike the organisms of the permanent pond which can be

persistent, the organisms of temporary pond has to re-

establish when the pond fills up with water, grow, reprod-

uce and produce oversummering forms. All this has to be

performed and completed before the pond dries out again.

Such a demand of the environment could lead to selection

of species able to cope with the rigors of the environment.

Organisms able to develop rapidly could be at an advantage.

Rzoska art land- owe, 1966) had data of temporary pools

in Africa indicating that the growth rates of some of the

crustacea were very high. It is noteworthy that I saw

the presence of larger individuals in calanoids and

amphipods in the temporary pond. The calanoids produced

more.'eggs than that in the permanent pond, probably, to

compensate for a possible high mortality in the eggs during

summer drought. The extreme resistance to desiccation of

the ephippia of Daphnia to a fairly wide range of osmotic . ~. , .

pressure was-also verified. These obser'vations indicate

well developed adaptations which could have resulted from

selection by the environment.

The nec-sity for organisms in the temporary pond to

establish and disappear becomes a cyclic event leading to

the observation of dominance and succession. The phenom

anon of succession would undoubtedly be beneficial to all

species concerned in a ecosystem for it reduces inter-

specific competition for food and space.

The most obvious and interesting observation of

interrelationships among organisms was that of the birds

and their activities in the temporary pond. The water-

fowl and Plovers commenced breeding in late winter. At

about this time, the Swamp Harrier, a predatory bird,

made occasional visits to the pond, but was always driven

back to the river where it came from. The arrival of

Tree-Martins coincided with a time when there was/con-

siderable number of insects in the air.

.-

VIII References.

General References

American Public Health Association (1960): Standard

Methods for the Examination of Water and Wastewater.

1 1 th Ed. (New ~orlc) . Anderson, G.C. (1958): "Some limnological features of a

shallow saline meromictic lake." Limnol. Oceanom.:

Barclay, M.H. (1966): An ecological study of a temporary

pond near Auckland, New Zealand. Aust. J. Mar.

Freshwat. Res. z, 239-58. - Bayly, I.A.E. (1967): The general biological classifica-

tion of aquatic environments with special reference

to those of Australia. In "Australian Inland Waters .

and their Fauna." ( ~ d . A.H.weatherley) (~ustralian

National University Press, ~anberra).

Byars, J.A. (1960) : A Freshwater Pond in New Zealand.

Aust. J. Mar. Freshwat. Res. , 222-40.

Cole, A.E. (1932): "A method for determining oxygen

content of mud at the bottom of a pond."

Ecology, 2, 51-3.

Cole, G.A. (1966): "Contrasts among Calanoid Copepods from - -

Permanent and Temporary Ponds in Arizona." The Am.

Midland Naturalist, s, 351-368. -

Dendy, J.S. (1963): Farm Pond. In "Limnology in North

America." ( ~ d , D . G . F ~ ~ ~ ) (~niv. of ifisconsin Press.)

Erikensen, C.H. (1~66): Diurnal limnology of two highly

turbid puddles. Verh. int. Ver. Limnol., 16, 507-14. e:

Fogg, G.E. (1965): Algal Cultures and Phytoplankton

Ecology. h he Athlone Press, Univ. of London.) Frith, H.J. (1967): Waterfowl in Australia. ( ~ n ~ u s and

Robertson, Sydney.)

George, M.G. (1961): Diurnal variation in two shallow ponds

in Delhi, India." Hydrobiol., l8, 265-73. -

Hartland-Rowe, R. (1966): The fauna and ecology of

temporary pools. Verh. int. Ver. Limnol., l6, 577-84. -

Historical Records of Australia (1921): Vol. 2. h he Library Committee of the Commonwealth Parliament.)

Hutchinson, G.E. A Treatise of Limnology. Vol. 1 (1957)

Vol. 2 (1967) (~ohn Wiley and Sons: New ~ork.)

Kenlc, R.(1949): The animal life of temporary and permanent

ponds in southern Michigan. Misc. Publs. Mus. 2001.

Univ. Mich., z, 1-66. Lewin, R.A. (1962): Physiology and Biochemistry of Algae

" (~cademic press: ' ~ e w York and London. )

Littlejohn, M.L. (1963): Frogs of el bourne Area. The . .

Victorian Naturalist, 2, 296-304. . . . . . . . . .

Lund, ' J . w . G . (1965) : The Ecology of' the Freshwater Phyto-

plankton. Biological Reviews, 40, 231-93. -

McLaren, I.A. (1965): Some relationships between tempera- -

ture and egg size, body size, development rate and

fecundity of the copepod Pseudocalanus. Limnol.

Oceanopr., 2, 528-38. Mozley,.A. (1932): A biological study of a temporary

pond in Western Canada. Am. Nat., 66, 236-49. - Murray, J. (1911): The annual history of a periodic pond

Int. Revue. ges. Hydrobid. Hydrogr. 2, 300-10. - Odum, E.P. (1961): Fundamentals of Ecology 2nd Ed.

(~.~.~aunders Company: Philadelphia and London.)

Petersen, W. (1926): Seasonal succession of animals in

a Chara cattail pond. Ecology, 2, 371-7.

Reid, G.K. (1961): "Ecolo,~ of Inland Waters and Estuaries." -

(~einbold Publishing Corporation: New York

Chapman and Hall Ltd., London.)

Ruttner, F. (1953): Fundamentals of Limnology. -

(university of Toronto Press: Canada.)

Smith, R. L. (1 966) : Ecology and ~ieid Biology. ( ~ a r ~ e r

and Row: New York and London.)

Stout, V.M. (1964): Studies on temporary ponds in

Canterbury, New Zealand. Ver. int. Ver. Limnol.,

s, 209-14. Styczynska-Jurewicz, E. (1966): Astatic water bodies as a

characteristic habitat of some parasites of men and

animals. Vcrh. int. Ver. Limnol., l6, 604-11.

Tasmanian Government Gazette (1920): (1941).

Villee, C.A. (1967): Biology. 5th Ed. (w.B.Saunde~-a

C O ~ P any

Ward, E.B. (1940): A seasonal poluation study of pond

.Ef~tomostraca in the Cincinnati region. Am. Midl.

w, 3, 635-91. - Welch, P.S. (1935): Limnology. (~c~raw- ill Book Co.:

New York and on don.)

----------- (1948): Limnological Methods. (~c~rae- ill

Book-Co.: New York, Toronto and London.)

References used for identification of Organisms.

Bayly, I.A.W. (1964): A revision'of. Australian species of

freshwater genera Boeckella and Hemiboeckella

(copepoda: ~alanoida) Aust. J. Mar. Freshwat. Res.,

l-5, 180-238. - Birds of Australia, The Official Checklist, (1926): 2nd Ed.

( ~ o ~ a l Australasian Ornithologistls Union: Melbourne.)

Boving, A.G., and Craighead, F.C. (1953): Larval forms of

the Order Coleoptera. (~rooklyn Entomological -.

Society: New York.)

curtis,, W.M. The StudentlsFloraof Tasmania. Vol. 1 - -

(1956) voi. 2 (1963) Vol. 3 (1967) (~overnment . .

Printer: asma mania. )

Dobrotworsky, N.V. (1966): Mosquitoes of Tasmania and

Bass Strait Island. Proc. Linn. Soc. N.S.W., 2,121-46.

Guiler, E.R. (1952): A list of the crustacea of Tasmania.

Records of the Queen Victoria Museum. Launceston,

Tasmania, 2 , 15-44. ginghbrn, J.R. (1956) : The Snake/ of Australia. (Angus

l

and Robertson: Sydney.)

Littlejohn, M.J. (1963): Frogs of the Melbourne Area.

The Victorian Naturalist, 2, 269-304.

Mellanby, H. (1963): Animal Life in Fresh Water 6th Ed.

(~ethuen and Co. Ltd.: London.)

Parker, T.J., and Haswell, W.A. (1963): A Text-book of .. ~

Zoology. 6th Ed. Vol. 1. (~d. 0.~0wenstein)

(~acmillan and ~o.~td. : London. )

Salmon, J.T. (1951): Keys and Bibliography to the

Collembola. Zoology Publications from Victoria Univ.

College. No. 8.

Sharland, M. (1958): Tasmanian Birds. ( ~ n ~ u s and Robertscn:

Sydney. )

Smith, G.W. (1909): Fresh-water crustacea of Tasmania.

Tres. Linn. Soc., ( k ) , 61-92. - Tillyard, R.J. (1926): The Insects of Australia and New

Zealand. (~ngus and Robertson: Sydney.)

Ward, B.B. and Whipple, G.C. (191 8) : Fresh-water Biology.

1sC Ed. (~ohn Wiley and Sons: New York.)

........................... , (1959): Fresh-water Biology. - .

2nd Ed. (~d. W.T.~dmondson) (~ohn hliley and Sons:

New ~ork. ) - Whitley, G.P. (1960): Native Fresh-water Fishes of

- Australia. (~acaranda Press: Brisbane.)

Williams, W.D. (1962): The Australian Fresh-water . .

Amphipods. Aust. J. Mar. Freshwat. Res.,-2, 198-216.

.Wills, J.H. (1962) :_ A HandbookA~o Plants In Victoria.

Vol. 1 elbo bourne Univ. Press.)

IX Appendix.

Fig.32- Dodmnt Dlatms of Granton Iagoon, 1967.

Diatom. %. 1 a

Dia tom, Sp. - 3 a

a - Valve vim, b - Girdle view, r - b p h e , [m - Ohlmo~hst .

Invertebrates of Granton La~oon'

e ens it^ expressed in number per 100 cc.) Date 7.4.67 20.4.67 26.4.67 3.5.67 18.5.67 5.6.67 26.6.67

Macrostornidae, Sp.2 - - - - - - 0.08

Tubif icid

Daphnia carinata

Macrothrix burstalis . .

Alonella nasuta

Ostracod, Sp.'l ..

Ostrocod, Sp.2

Cyclops SJ;.

Bdeckella -triarticulata

Austrochiltonia austraiis . . . . . . .

Collembilid

Notonecticid - - - - 0.13 - - Corixid 0.63 - - 0.05 - - 0.02 - Rhantus =. - - - - - 0.10 0.02 + Aedes cani~torhyncus - - 2.00 0.10 3.78 1.65 0.56

. . 7 Tanypus &. 1.63 0.13 0.28 - - . - 0.24 0.98 Chironomus B. 6.63 4.35 1.40 7.12 0.68 3.11 11.84 Epliydridae - 0.56 0.64 - 0.50 0.09 1-75

Invertebrates of Granton Lagoon (continued)

Date 3.7.67 24.7.67 14.8.67 5.9.67 26.9.67 16.10.67 Macrostomidae, Sp.2 2.82 3.84 8.88 0.84 0.17 0.65 Tubif icid 22.13 72.88 221.13 67.11 79.14 95.75 Daphnia carinata 2.48 1.74 2-77 1.03 1.50 1.08

Macrothrix burstalis - - - - 0.03 0.02

Alonella hasuta - - - - 0 s.03 - Ostracod, Sp.1 - 1.30 0.13 0.13 0.27 0.01

Ostrocod, Sp.2 - - .- - - - Cyclops a. 0.17 3.68 27 50 3.73 0.10 1.03 Boeckella triarticulata 0.25 0.54 3-27 4.57 2.14 0.59 Austrochiltonia australis 15.49 4.62 1.41 0.86 0.27 0.30 Collembilid 0.04 + + 0.10 + + Notonecticid - - - - + 0.01

Corixid . 0.01 0.05 - - - . + Rhantus a 0.11 0.06 - - - - Aedes camptorhyncus 2.02 0.32 0.41 0.02 + + 7 Tanypus 9. 5.94 2.24 5.31 2.13 1.44 4.43 Chironomus a. 56.25 26.75 53.88 20.89 29.56 297.75 Ephydridae 9.69 3.44 2.50 1.09 0.01 + .

- indicates absence + I, present, but less than .O1 per 100 cc.

Aves of Granton L a ~ o o n

b bun dance in absdiute'numbers~-.counts made at 1 1 a.m., Eastern Standard Time)

Date 7.4.67 20.4.67 26.4.67 3.5.67 18.5.67 .5.6.67 26.6.67 . . . . . . . . . . . . . . . . . . . . . . . . . . . , .

Spur-winged Plover 97 200 7 0 120 302 40 10

Silver Gull 8 - 5 200 12 12 2 1 5 Native Hen - - - 1 1 4 3 2

Bald Coot 1 3 1 1 2 1 3

White-faced Heron 1 1 - - - - - Blue-winged Shoveler - - - - - - - Chestnut Teal - - 2 3 10 3 8 3

Black Duck - - - - - 43 14

Black Swan

Swamp Hawk

Raven .

House Sparrow

Starling

Chat

Aves of Granton Lagoon (continued) , . - -

Date 3.7.67 24.7.67 14.8.67 5.9.67 26.9.67 16.10.67 . . . . ~. . . . . . . .

Spur-winged Plover 4 50 - 2 21 6 Silver Gull 14 15 40 4 2 2

Native Hen 4 3 - 2 1 2

Bald Coot 3 2 2 2 1 5 White-faced Heron - - 1 - - - Blue-winged Shoveler - - - 12 - - Chestnut Teal 30 20 20 3 8 17 27

Black Duck

Black Swan

Swamp Hawk - - - - 1 1

Tree-Martin

Raven

House Sparrow

Starling

Chat

Physiochemical Features of Granton Iagoon

Date of Sampling 7.4.67 20.4.67 26.4.67 3.5.67 18.5.67 5.6.67 26.6.67

Depth. (cm) - - - - 2.0 6.0 14.0

Temp. OC A i r 23.0' 15. o0 l3.7O 15.0' 11.2O 11.2~ 10.4'

H2° 21.5' l4.5O 17.0' 16.0' 10.9' 11.5~ 8.9' Bottom 20. o0 U. 5O 17.0' 16.0' 10.9' 1 1 . 2 O 8.9'

Physiochemical Features of Granton La~oon (continued)

Date of Sampling 3.7.67 24.7.67 U.8.67 5.9.67 26.9.67 .16.10.67

Depth (cm) 20.0 33.0 33.0 34.0 34.0 33.0

0 Temp. C A i r 4.9O 1 0 . 0 ~ 10. o0 13.5~ 13.9~ 16.2'

H20 4.5O 9.1' 6.0' 12.2O 12.2~ 17.0'

5.1° 9.0' 6.0' 10. o0 10.8' Bottom 15.9'

Aves of a Dart of River Derwent, adjacent to Granton L a ~ o o n . . . . b bun dance given in absoiute.numbe+s.- counis'made at'5 p.m. Easeern

Standard Time)

Date 18.5.67 5.6.67 26.6.67 3.7.67 24.7.67 14.8.67 5.9.67 26.9.67 16.10.62

Hoary-headed 28 7 0 50 3 25 4 2 94 - Grebe

55

Black Cormorant - 13 - - - 1 1 - - 8

White-breasted 4 17 2 18 17 20 13 40 - Cormorant

- - 4 Spur-winged - - - - - - Plover

Silver Gull 31 0 - 2 - - 4 - - 19

Coot 27 0 390 118 550 400 600 1030 240 - 5 6%

- - 56

- - 30 53 chestnut Teal

e

19 12 - - 24

Black Swan 432 364 2&6 450 352 270 140 40 25

Plate 3. Ca.lvertls Lagoon, aerial view, March 1965. Scale Icm. = 124.4 m.

UNIVEBSFIII OF TASMANU LIBRARY '

&;on\ RESERVE 'IbL item belongs m tha Resave Collection. This E o l b c t i r m E o a t a i n s ~ . l i n h i ~ d c m a r d . LOANS Tbis item can d y be bmmwed fm 2 horn -rboday. O v c m i g h r l a r m r n ~ ~ t b c t u ~ o t c h s l i i r r y ' s ~ e k h d a y . TbQalomr M U S T b e r r n m r c d i h s o m d a y d ~ . t c b e b c ~ dtbLbufsbudDaghoon PENALTIES Apply im Intc tern iDshding Ourrid charges. S c e t t r l i b r m J G n i d r ~ ~ ~ BOOKINGS Y o n c s a ~ a ~ f o r t h i . i u m i f y o u rhatollrsilat.spc&crim. A s L t b c p . f f a t t h c - -mwyon. Qusarss p ) c . M p b m r t b s ~ l i i An (&ingbs SmiW LIbay (03) 6226 4376 Bhm%Ia L M (U3) 62% 22653 ~ L i l r a y Cm) 6226 4813 LaumsAm-Libnn 103) 6324 3276