Response of Attached Algae to Whole-Lake Fertilization Experiments in Five British Columbia Coastal Lak.es

K. R. S. Shortreed and J. G. Stockner

Department of Fisheries and the Environment Fisheries and Marine Service Resource Services Branch Pacific Environment Institute 4160 Marine Drive West Vancouver, British Columbia V7V 1 N6

August 1978

Fisheries & Marine Service Technical Report No. 802

,

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• Cover deSign by Christine Rusk

Fisheries and Marine Service

Technical Report 802

August 1978

RESPONSE OF ATTACHED ALGAE TO WHOLE-LAKE FERTILIZATION

EXPERIMENTS IN FIVE BRITISH COLUMBIA COASTAL LAKES

by

K. R. S. Shortreed and J. G. Stockner

Department of Fisheries and the Environment

Fisheries and Marine Service

Resource Services Branch

Pacific Environment Institute

4160 Marine Drive

West Vancouver, British Columbia V7V lN6

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(c) Minister of Supply and Services Canada 1978

Cat. no. Fs 97-6/802 ISSN 0701-7626

iii

ABSTRACT

Shortreed, K. R. S.,and J. G. Stockner. 1978. Response of attached algae to whole-lake fertilization experiments in five British Columbia coastal lakes. Fish. Mar. Ser. Tech. · Rep. 802: 25 p .•

Characteristics of attached algal growth were monitored in six oligotrophic lakes in south coastal B.C. using Plexiglas plates as a substrate. Nitrate and phosphate were added weekly to areas within five of the lakes. The additions produced attached algal biomass within fertilized areas up to an order of magnitude greater than biomass outside those areas. Diatoms were dominant, principally Achnanthes minutissima~ FragiZaria vaucheriae~ TabeZZaria spp., and Eunotia spp. The most common non-diatom alga was Mougeotia spp. Species composition was not measurably altered by fertilization in any of the five lakes. Nitrate and phosphate were utilized rapidly and concentrations within fertilized areas were similar to those without. Although N:P ratios occasionally dropped below 5:1, blue-green algae were of little importance.

Clayoquot Arm in unfertilized Kennedy Lake had mean chlorophyll a values (0.06 mg'm- 2 ) lower than previously recorded for any biological system.

" ,-RESUME

Shortreed, K. R. S., and J. G. Stockner. 1978. Response of attached algae to whole-lake fertilization experiments in five British Columbia coastal lakes. Fish. Mar. Serv. Tech. Rep. 802: 25 p •.

Les auteurs ont etudie la croissance d'algues fixees sur des assiettes de Plexiglas, dans six lacs oligotrophes du sud de la region cbtiere de la C.-B. Dans certaines parties de cinq de ces lacs, des nitrates et des phosphates ont et~ ajoutes hebdomadairement. Dans les zones ainsi fertilisees, la biomasse des algues fixes a pu atteindre un ordre de grandeur de plus que les autres. Les diatomees y dominaient, principalement Achnanthes minutissima, Fragilaria vaucheriae, Tabellaria spp. et Eunotia spp. Apres les diatomees, l'espece la plus courante etait Mougeotia spp. Dans aucun des cinq lacs fertilis~s, la composition des esp~ces n'a varie de fa~on sensible. Les nitrates et les phosphates y ont ete assimiles rapidement, et leur concentration s'y est maintenue semblable ~ celIe des zones privees de fertilisation. Quand Ie rapport N:P est descendu sous 5, les algues bleues sont demeurees peu importantes.

Dans Ie bras Clayoquot du lac Kennedy non fertilisl, la teneur moyenne en chlorophylle a (0,06 mg . m-2) a ete inferieure a toutes les valeurs

, , " precedemment enregistrees dans les autres lacs.

INTRODUCTION

In 1977 the Lake Enrichment Group in the Sa1monid Enhancement Program fertilized five lakes in south coastal British Columbia (Fig. 1). Four of the lakes are important rearing areas for juvenile sockeye salmon (Oncorhynchus nerka), while one has a sizeable sports fishery for landlocked sockeye (kokanee). Concurrent with the fertilization was a comprehensive sampling program on the five lakes and also on Kennedy Lake, to be fertilized in 1978. Mathisen (1972) studied juvenile sockeye production in Alaskan lakes and identified the littoral zone of lakes and its biocenosis as the key to early fry survival. Thus, this investigation of attached algal growth in the littoral zone of the study lakes was considered an important part of the program. Although the response of attached algae in lakes to altered nutrient concentra­tions has been well studied (Fox et al. 1969; Stockner and Armstrong 1971; Evans and Stockner 1972; Stockner et a1.1972; Ennis 1975), few investigations have had the opportunity of observing changes in attached algae in such a large-scale fertilization program. For these reasons, it was desirable to further our understanding of attached algal response in fertilized lakes by monitoring their composition, succession, and biomass in 1977, the first year of fertilization, and in subsequent years of the program.

DESCRIPTION OF THE STUDY AREA

All six lakes lie in the cool Mediterranean-type climate of the B.C. coast, where cool summers and mild, wet winters prevail (Table 1, Fig. 1). The watersheds of Great Central, Hobiton, Kennedy and Henderson lakes lie in the western hemlock biogeoclimatic subzone with annual rainfall ranging from 2.8-5.0 m. Mohun Lake lies in the rain shadow of the coastal mountains and Douglas fir is the dominant vegetation. Long Lake on the central mainland coast receives high rainfall and more extreme winter temperatures.

METHODS

BIOLOGICAL

Samplers consisted of Plexiglas plates (0.7 X 10 X 15 cm). On both sides of the plate a 100-cm2 quadrant was marked and used as the sampling area. Samplers were suspended vertically 1 meter below styrofoam floats and anchored to concrete blocks. In each lake one sampler was placed within the zone of fertilization and one or two samplers outside it, although in the smaller lakes (Mohun and Hobiton) differences between zones were not as marked as in the larger lakes.

Monthly sampling consisted of scraping all accumulated growth from both sides of a plate into a glass jar filled with distilled water. Samples were kept dark and cool and were transported to the laboratory the same day. In the laboratory the contents of a jar were split in half, and one portion fixed with Lugol's acetate solution. The . other half was split again, and one of

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these portions was filtered onto an ashed and weighed 5.5-cm Whatman glass fiber filter, placed in a labelled aluminum weighing dish, and frozen. Frozen samples were dried overnight at 90 C, weighed, ashed at 480 C for 4 h in a muffle furnace, and weighed again. Results are expressed as ash free dry weight (AFDW) in g.m- Z• The other portion was filtered onto a 47-mm diameter AA Millipore filter and frozen. Chlorophyll was extracted using lllethods of Golterman (1969). Filters were macerated in a tissue grinder with 10 ml of 90% acetone, and the filtrate analyzed for chlorophyll a with a Turner Model 111 fluorometer. Chlorophyll a concentration was expressed as mg.m- Z.

A portion of the algae fixed with Lugol's was counted on a Wild M40 inverted plankton microscope to determine relative abundance of major algal groups and to identify non-diatom algae to the genus level. Permanent quantitative Hyrax mounts of diatoms were made and counts from these were converted to number of diatoms·m-z using methods described by Stockner and Armstrong (1971). Total algal cells·m-z were calculated by applying abundance of diatoms relative to other algal groups (from inverted microscope counts) to the diatom counts.

PHYSICOCHEMICAL

Physicochemical data were collected twice monthly. All monitor stations were located within fertilized areas, except those on Kennedy Lake and Station 1 on Great Central Lake. Transmission of light was measured with a 20~' cm Secchi disc and with a Montedoro-Whitney LMT8A illuminance meter. Natural log of light intensity was plotted against depth and a line fitted to the points gave the mean extinction coefficient (k). Chemical analyses were performed at Pacific Biological Station in Nanaimo, B.C. according to the methods of Golterman (1969).

RESULTS

Mean nitrate (N03-N) concentrations ranged from 1.0 ~g.L-l in the unfertilized area of Great Central to 13.2 in the fertilized area of Long Lake, while phosphate (P04-P) ranged from 1.8 ~g.L-l in the unfertilized area of Great Central to 3.6 in the main arm of Kennedy. Silicate (Si04-Si) was lowest (538 ~g.L-l) in Henderson and highest in Hobiton Lakes ('fable 2).

All values of biological variables (chlorophyll a, algal numbers, algal volume, ash-free dry weight) were lowest in unfertilized Kennedy Lake and highest in the fertilized zones of Long and Henderson Lakes (Table 2). Within lakes, stations in the fertilized areas had an algal biomass up to one order of magnitude greater than those outside it (Fig. 2). In Mohun and Hobiton, samplers were relatively close together and within lake variation was not marked. In Kennedy Lake, Station 3, located in the shallow main basin, was more productive than Stations 1 or 2 located in the deep Clayoquot Arm. In all lakes, greatest algal biomass was recorded in September.

Diatoms formed greater than 75% of the volume of attached algae in all lakes, and on some occasions over 90% (Table 2). Common diatoms were Achnanthes minutissima~ Tabellaria fenestrata~ T. flocculosa~ Fragilaria

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crotonensis~ F. vaucheriae~and Anomoeoneis serians. In Long Lake, Eunotia lunaris~ E. tenella~ and E. sudetica were common (Fig. 3). Dominant forms in each lake are ranked in descending order of dominance in Table 3. Of the non-diatoms, only the filamentous green alga Mougeotia sp. was an important contributor to total biomass.

Although the data are too limited to permit a detailed discussion of seasonal succession, some trends are evident (Fig. 3). Fragilaria crotonensis was common early in June in most lakes but decreased in importance by the end of August, concurrent with the increase in abundance of F. vaucheriae. Cyclotella stelligera was common in some lakes, but only in the early part of the study. Tabellaria fenestrata and T. flocculosa were common and occasionally dominant, but no definite pattern of succession was apparent between these species. Mougeotia sp. was most abundant in late August. Differences in algal assemblages among lakes were greater than differences between stations within lakes (Fig. 3). A species list is presented in Table 4.

DISCUSSION

Despite weekly additions of nitrate and phosphate to the lakes, concentrations of N03-N and P04-P within fertilized areas were similar to those without, indicating the rapid biological utilization of these essential ions by both planktonic and benthic algae. Concentrations of NOr-N and P04-P seldom exceeded 3 ].lg.r,-l and were frequently less than 0.5 ].lg·L- , well below the critical concentration of 10 ].lg·L- 1 P04-P which Dillon and Rigler (1975) found could cause nuisance algal problems to develop. The chemistry of the six lakes is discussed in detail by Stockner et al. (unpubl. MS), but in general both nitrate and phosphate remained at or near detectable limits with N:P ratios lower than 5:1.

Of the six lakes, only in Long Lake was a Secchi disc measurement less than 5 m recorded, and in that lake the minimum was 3.5 m. Since the samplers were at a depth of 1 m, light could not be considered a limiting factor in this investigation. Although nitrogen and phosphorus were added to the lakes in a ratio of 10:1, N:P ratios were consistently less than 10:1 in surface water samples from the lakes. The rapid biological uptake of nitrogen plus its slow regeneration rate relative to phosphorus, suggests that the low nitrogen concentration was one of the primary factors limiting attached algal growth in our study lakes.

Although N:P ratios were often in the range found by Schindler and Fee (1974) to stimulate production of blue-green algae, these forms were of minor importance in the attached algal assemblages. It seems likely that production of "nuisance" algae both in the plankton and in the littoral assemblage was prevented simply by the very low incipient nutrient levels. An increase in nutrient loading would be likely to promote deleterious effects unless the increase was accompanied by an increase of the N:P ratio to at least 15:1. It is likely that an increase in nitrate loading, to increase the ratio from <5:1 to 15:1, would cause an increase in algal biomass without any increase in phosphate levels, similar to the effects observed in Carnation Creek by Stockner and Shortreed (1978).

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All stations in the study had lower chlorophyll levels t han the 70 mg·m- 2 average found for periphyton in the south arm of Kootenay Lake, while only the more productive stations had as high an average as the oligotrophic north arm of Kootenay (Ennis 1975). Of the lakes studied by Stockner et al. (1972) in the Okanagan Basin, only Kalamalka had chlorophyll a values as low as those in the fertilized areas of the study lakes. Chlorophyl l a concentrations in Clayoquot Arm of Kennedy Lake were lower than any yet repo rted in the literature, lower even than ultra-oligotrophic Carnation Creek (Stockner and Shortreed 1976, 1978). Carnation Creek's average algal biomass was 1.9 mg·m- 2 as opposed to 0.06 mg·m- 2 in Clayoquot Arm of Kennedy Lake . In four lakes of the Experimental Lakes Area (ELA) in northwestern Ontario, Stockner and Armstrong (1971) found chlorophyll a levels similar to those of the more productive areas of our study lakes.

Organic ash-free dry weights followed a seasonal pattern similar to chlorophyll. All lake areas had lower values than those found by Ennis (1975 ) in Kootenay Lake, by Fox et a1. (1969) in Lake Superior, or by Stockner and Armstrong (197l)in the ELA. Only values reported by Stockner and Shortreed (1976) in Carnation Creek are as low as those found in the most productive fertilized areas of the study lakes.

Attached algal volume and algal numbers were also similar to many reported values for oligotrophic lakes, excepting C,layoquot Arm of Kennedy Lake, which had lower values than any found in the litera t ure.

Achnanthes minutissima has been found by several investigators to be important or dominant in temperate lakes of varying trophic status (Godward 1937; Fox et al. 1969; and Stockner and Armstrong 1971), and i t s highly ubiquitous nature is reflected in its importance in five of the six study lakes (Table 3). The dystrophic nature of Long Lake was clearly indicated by the dominance of several species of Eunotia in the littoral assemblage. Patrick and Reimer (1966) state that these species are acidophilic with a preference for ponds, bogs and humic stained waters. Although Ennis (1975) found FragiZaria vaucheriae to be an indicator of decreasing eutrophy in Kootenay Lake, in this study it was most abundant in Long Lake, the most productive of the six study lakes.

In conclusion, fertilization has caused large increases in biomass of attached algae within fertilized areas of the study lakes, while maintaining algal species composition within fertilized areas similar to that without. Since most of the study lakes have limited littoral areas, it is likely that the percentage of added nutrients utilized by attached algae is relatively small. However, the response of attached algae to fertilization is striking , and may have a beneficial effect on the littoral fauna of the lakes, which in turn may be beneficial to sockeye salmon fry, particularly in those lakes with beach spawning populations of adult sockeye.

ACKNOWLEDGEMENTS

The authors thank Messrs. R. Brandstaetter, E. MacIsaac, and K. Stephens for invaluable assistance in the sampling program and in analysis of data. E. MacIsaac also drafted the figures and assisted in data collation.

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REFERENCES

Dillon, P. J., and F. H. Rigler. 1975. A simple method for predicting the capacity of a lake for development based on lake trophic status. J. Fish. Res. Board Can. 32: 1519-1531.

Ennis, G. L. 1975. Distribution and abundance of benthic algae along phosphate gradients in Kootenay Lake, British Columbia. Verh. Internat. Verein. Limno1. 19: 562-570.

Evans, D., and J. G. Stockner. 1972. Attached algae on artificial and natural substrates in Lake Winnipeg, Manitoba. J. Fish. Res. Board Can. 29: 31-44.

Fox . J. L., T. O. Odbaug, and T. A. Olson. 1969. The ecology of periphyton in western Lake Superior. Part I - Taxonomy and distribution. Bull. Water Resour. Res. Center, Univ. Minnesota 14: 99 p.

Godward, M. 1937. An ecological and taxonomic investigation of the littoral algal flora of Lake Windermere. Ecology 25: 496-468.

Go1terman, H. L. (ed.). 1969. Methods for Analysis of Fresh Water. IBP Handbook 8.

Mathisen, O. A. 1972. Biogenic enrichment of sockeye salmon lakes and stock productivity. Verh. Internat. Verein. Limno1. 18: 1089~1095.

Patrick, R., and C. W. Reimer. 1966. The Diatoms of the United States, I. -Acad. Na tur. Sci. Philadelphia, Monogr. 13: 688 p.

Schindler, D. W., and Fee, E. ~ 1974. Experimental Lakes Area: who1e1ake experiments in eutrophication. J. Fish. Res. Board Can. 31: 937-953.

Stockner, J. G., and F. A. J. Armstrong. 1971. Periphyton of the Experimental Lakes Area (ELA), northwestern Ontario. J. Fish. Res. Board Can. 28: 215-229.

Stockner, J. G., M. Pomeroy, W. Carney, and D. L. Findlay. MS 1972. Studies of Periphyton in Lakes of the Okanagan Valley, British Columbia. Canada­British Columbia Okanagan Basin Agreement, Okanagan Study Committee, Prelim. Rep. No. 33: 21 p.

Stockner, J. G., and K. R. S. Shortreed. 1976. Autotrophic production ir, Carnation Creek, a coastal rainforest stream on Vancouver Island, British Columbia. J. Fish. Res. Board Can. 33: 1553-1563.

Stockner, J. G., and K. R. S. Shortreed. 1978. Enhancement of autotrophic production by nutrient addition in a coastal rainforest stream on Vancouver Island. J. Fish. Res. Board Can. 35: 28-34.

Table 1. Morphometric and physical data of study lakes.

Total Mean Temperature Annual Annual (0 C) Elevation Drainage Residence Mean Lake

Lake Precipi- Snowfall Latitude Longitude Area Time Depth Area Remarks tation (em)

Mean Mean (m) (km 2 ) (yr) (m) Ckm2 ) (em) Summer Winter

Great 192 81 16.1 2.6 49 0 22' 125 0 IS' 82 308 34 212 45 Small littoral zone.; ext en-Central sive logging; some recre-

ational activity (fishing, cottages, one resort).

Henderson 302 42 13.7 5.2 49 0 05' 125 0 02 ' 15 144 6 109 17 Small littoral zone; extensive logging; no other activities.

Hobiton 268 40 13.6 5.0 48 0 45' 1240 49' 15 48 2 36 3.6 Extensive littoral zone ill! parts of lake; no recreation al or industrial actiyity.

Kennedy 302 42 13. 7 5.2 -19 0 08' 125 0 12 128 4 50 16.8 Some logging: littoral zone (Clayoquot minimal in Clayoquot Al'm Arm) but large in main arm; very

little recreation.

Long 173 71 12.8 3.5 51 0 1-1' 127 0 10' 15 369 3 73 16.0 Fisheries camp on lake; no industrial or recreational activity; some patch logging in '50s.

Mohun 154 104 17.4 1.3 500 0-' 125 0 30' 200 27 7 14 6.3 Extensive logging; large li ttoral acne in parts of lake; extensive sport fishery for kokanee.

Table 2. Mean attached algal biomass and numbers and salient physical and chemica] factors in study lakes, 1977.

Lake and Chlorop1)yll-a AFDWa Algal no Algal Vol % Diatoms Secchi N0 3 (N) P04(P) Si0 4 (Si) Station mg.m 2 g'm- 2 x10 8 'm- 2 cm 3. m - 2 of vol D~ptj'l llg' r 1 llg' r 1 llg· r 1

I.. lU )

Great 1 0.15 0.15 1. 54 0.11 83 13.5 1.0 1.8 942

Central c 2 2.22 0.23 17.31 0.86 90 12.5 2.1 1.9 931

3 0.31 0.24 3.50 0.14 86 - - - -

Henderson 1 1. 65 b 0.24 11. 70 l. 05 95 - - - -c 2 16.6S b 1. 40 73.36 6.28 76 9.0 7.3 2.5 538 c 3 7.09 0.65 42.93 1. 46 92 - - - -

Hobiton cl l. 84 0.19 61. 43 l. 29 76 - - - -c 2 2.56 0.42 25.63 0.75 77 7.0 l.1 2.1 1272

Kennedy 1 0.07 0.14 1. 02 0.04 100 8.5 3.5 1.8 965

2 0.05 0.07 0.35 0.02 82 - - - -3 0.48 0.17 5.52 0.09 77 7.0 1.3 3.6 933

Lon g c l 16.72 0.85 27.15 1. 36 76 5.0 13.2 2. 5 785

2 3.8 7 0.33 8.34 0.31 83 - - - -

Mohun c l 4.49 0.90 29.28 2.15 96 9 . 0 6.8 2. 3 937 c 2 2 .8 3 0.42 32.89 2.02 94 - - - -

~Ash - fre e dry we i ght. Stations sampted on only two dates.

CSt ations affe c ted by fer t i l iza t ion,

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Table 3. List of dominant diatoms from ]9 77 per i ph ylon study . ranked in diminishing order of numeri ca l abundance.

A. GREAT CENTRAL LAKE Stn. 1

1 . Achnanthes minutissima 2 . Fr agilaria crotonensis 3 . Tabellaria fenestrata 4. Fr agilaria vaucheriae S. Tabellaria flocculosa 6. Navicula sp.1

B. HENDERSON LAKE Stn. 1

Stn. 2

1 . Achnanthes minutissima 2. Tabellaria flocculosa 3 . Tabellaria fenestrata 4. Fragilaria crotonensis S. Fragilaria vaucheriae 6. Navicula s p. 1

1. Tabellaria flocculosa 1.

Stn . 2

Tabella ria fenest rata Achnanthes minutissima Tabellaria flocculosa Fragilaria c r otonensi s Fragilaria vaucheriae Diatoma elongatum

2. Achnanthes minutissima 2. 3. Tabellaria fenestrata 3. 4. Fragila r ia crotonensi s 4. S. Rhizosolenia eriensi s S. 6. Fragilaria vauche r iae 6.

C. KENNEDY LAKE

Stn. 1

1. Achnanthes minutissima 2. Tabella ria flocculosa 3. Anomoeoneis se r ians 4. Fr agiZaria crotonensis S. Tabellaria fenestrata 6. Fragilaria vaucheriae

D. LONG LAKE Stn.

1. Fragilaria vaucheriae 2 . Cyclotella stelligera 3. Eunotia lunaris var.1 4. TabelZa ria flocculosa S. Eunotia lunaris va r. 2 6. Anomoeoneis serians

E. MOHUN LAKE

Stn. 2

1. Achnanthes minuti ss ima 2. Cyclotella steZZigera 3. Tabellaria flocculosa 4 . Anomoeoneis se rians S. Fragilaria crotonensis 6. Tabellaria fenestrata

Stn. 2

1. Eunotia Zunaris (sm . ) 2. Fragilaria vaucheriae 3. Eu notia sudet~~« 4. TabelZaria flocculosa S. Eunotia tene lla 6. Tabellaria fenestrata

St n . 1 Stn . 2

1. Achnanthes minutissima 1 . Achnanthes minutissima 2 . TabelZa ria fenestrata 2 . TabelZaria fenestrata 3. Ano mo eD » eis ser ia n s 3. Anomoeoneis ser ian s 4. Navic u la sp . 1 4. TabeZlaria fZoccuZosa S. RhizosoZenia eriens i s S . NavicuZa sp.1 6 . Fragilaria crotonensis 6. FragiZaria crotonensis

F. HOBITON LAKE Stn . 1 Stn. 2

1. TabeZZa ria fZoccuZosa 1. TabeZZaria fZoccuZosa 2 . Achnanthes minutissima 2. FragiZaria c r otonen s is 3. Tabellaria fenestrata 3. Achnanthes minu tis sima 4. Anomoeoneis serians 4. RhizosoZenia erien sis S. FragiZaria vaucheriae S. FragiZaria vaucheriae 6. RhizosoZenia eriensis 6 . TabeZZaria fenestrata

Stn. 3

1. Achnanthes mi nutisaima 2. Fragi lari a vaucheria? 3. Tabellaria fe n es tp~ta 4. Fragilaria croton~nsis S. Tabella ria flocculoBa 6. Navicula sp. 1

Stn . 3

1. Achnanthes minutissima 2. Tabellaria floccutosa 3. Tabella ria fenestrata 4. Navicula sp.1 S. Fr agila ria cro~n8~aia 6. FragiZaria vaucheriae

Stn. 3

1. Achnan thes mi nutissima 2. Cy cZoteZla stellig.ra 3 . Fragilaria croton~~sis 4. Tab eZlaria f loc cwt o aa S. Tab eZZaria feneetrata 6. An omoeoneis serians

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Table 4. List of attached algal species and their respective volumes.

Diatoms

Achnanthes brevipes Cleve A. fZexeZZa (Klitz.) Brun. A. ZanceoZata (Breb.) Grun. A. minutissima Klitz. Achnanthes sp.l AmphipZeura sp.l Amphora ovaZis (Ehr) Cl. Anomoeoneis serians (Breb.ex Klitz.) Cl. Anomoeoneis sp. 1 AsterioneZZa formosa (Hantz) Grun. CycZoteZZa comta (Ehr.) Klitz. C. kutzingiana Thw. C. oceZata Pant. C. steZZigera Cl. & Grun. CycZoteZZa sp. 1 CymbeZZa turgida (Greg.) Cl. CymbeZZa ventricosa Klitz Cymbe Z Za sp. 1 Diatoma eZongatum (Lyngb.) Ag. D. hiemaZe (Roth) Heib. Eunotia exigua (Breb. ex Klitz.) Rabh. Eunotia Zunaris var. 1 (Ehr.) Grun. Eunotia Zunaris var. 2 (Ehr.) Grun. E. graciZis (Ehr.) Rabh. E. pectinaZis (KUtz.) Rabh. E. perpusiZZa Grun. E. sudetica O. Mull E. teneZZa Greve E. vanheurckii Patr. FragiZaria construens (Ehr.) Grun. F. crotonensis Kitt. F. vaucheriae (KUtz.) Peters FragiZaria sp. 1 FrustuZia rhomboides (Ehr.) De T. Comphonema acuminatum Ehr. C. constrictum Ehr. C. oZivaceum (Lyngb.) Ktitz. C. parvuZum Ktitz. Comphonema sp. 1 MeZosira isZandica O. Mull M. itaZica (Ehr.) Klitz. Meridion circuZare (Ralfs) V.H. NavicuZa tuscuZa (Ehr.) Grun. NavicuZa sp.l NavicuZa sp.2 Ni tzschia sp. 1

Continued

1000 800 100

30 50

4000 500 200 500 120 100

50 50 50 10

200 1000

400 250 500 100 500

2000 6000

700 200 200

50 500 120 120 100 100

3000 2500 2000

400 200

2000 90 90

250 2000

200 700

2000

Table 4. (Continued)

Nitzschi a sp . 2 Ni t z schia sp. 3

Diatoms

PinnuZaria braun ii Grun. C1. PinnuZaria sp. 1

- JI) -

RhizosoZenia erie nsis Nach (Hust.) R . Zongiseta Zach. RhopaZodia gibba (Ehr.) O. Mull. St auroneis sp. 1 Synedr a a c u s Klitz S . u Zna (N itz.) Ehr. Ta beZZar ia f e nestrata (Lyngb.) Kutz T . fZoc cu Zo s a (Roth.) Kutz

Non-diatoms

Anabaena sp. Chroococcus sp. Dinobr yo n sp. CZeoecapsa sp. Meris mopedia sp . Mo ugeotia sp. 1 Mou geotia sp. 2 OsciZ Zato r ia sp. Staura strum sp.

500 50

1500 5000 3000 3000 5000

700 2000 3300 3000 1000

15 4

250

50 500

5000 4

1000

- 11 -

BRITISH

51 COLUMBIA

5Ci'

ISLAND

o 100 km ---===--====-.....

128 127 124 123

Fig . 1. Map of location of the six study lakes.

-

~I

..c ()

- 13 -

5 GREAT CENTRAL LAKE

oL~~~~=---1

40 LONG LAKE

... - ........ Fertilized zone

0--0 Unfertilized zone

20

10

0~-4~~~~~----~----~----~ JULY AUG. SEPT. OCT.

Fig. 2. Chlorophyll a concentrations of attached algae in Long and Great Central lakes at stations inside and outside of fertilized zones.

15 -

LEGEND FOR FIGURE 3

SPECIES

Achnanthes minutissima

Anomoeoneis serians

Cyclotella stelligera

Diatoma elongatum

Eunotia lunaris var. 1

E. lunapis var. 2

E . sudetica

E. tenella

Fragilaria crotonensis

F. vaucheriae

Melosira islandica

Navicula s~. 1

Nitzschia sp. 1

Rhizosolenia spp.

Tabellaria fenestrata

T. flocculosa

Others a

SYMBOL

aAll species totalling <5% of the total population by

number are classified as "others."

- 17 -

GREAT CENTRAL LAKE

1001~--------~---------------------

%

STN.3

%

1001~~~ffiim~;::====:::=:J

75: __ _ 50 -'AA.I'"""

25

STN.2 100

%

Fig. 3. Percent relative abundance by number of cliatoms forming greater than 5% of the total population.

- 19 -

KENNEDY LAKE

1

%

STN.3 1

%

STN.2 1

%

Fig. 3. Percent relative abundance by number of diatoms forming greater than 5% of the total population.

- 21 -

HOBITON LAKE

100 0

75 %

50

25

0 STN.2

%

JUNE JULY

HENDERSON LAKE

100,-------~--------------------------~

75

25

Fig. 3. Pe r cent relative abundance by number of diatoms forming greater than 5% of t he to t al population.

- 23 -

MOHUN LAKE

100~--------------------------------~

% 75_m 25

STN.2 100~------------------------------~

%

Fig. 3. Percent relative abundance by number of diatoms forming greater than 5% of the total population.

o o

1

%

- 25 -

LONG LAKE

STN.2

JULY AUG. SEPT. STN.1

Fig. 3. Percent relative abundance by number of diatoms forming greater than 5% of the total population.