lecture 3 fw habitats_2 slides

8/10/2019 Lecture 3 FW Habitats_2 Slides

1/25

LSM3254 Ecology of Aquatic Environments

Freshwater habitats

Darren Yeo

Dept of Biological Sciences

Objectives

To learn about:

Selected freshwater habitats and associated limnologicalconcepts

Freshwater habitats in Singapore

Scope

Watershed

Lentic habitat lakes, swamps

Lotic habitat streams


References:Dodson, S. 2005.Introduction to Limnology. McGraw-HillChapters 2, 11


2/25

Watershed

Area of land that supplieswater to a lake or stream

= Area of land drainedbya lake or stream

Also known as catchmentor drainage

Note: Surface watershed maynot necessarily correspondwith groundwater watershed

Lentic environments

Standing water bodies

Lake

Large body of water, depth>3m, area >1-10 ha

Often shows thermalstratification

Pond Small body of water, area


3/25

Lakes

The majority of freshwater resides in just a few large lakesCan you name them?

~60% of the worlds fresh water in three areas

Lake parameters

Lake morphometrics

Shape, area, volume

Shore length (=perimeter)

Varies with shoreline development

E.g., for given area,

- More elongate, with rough, folded shoreline longer shore length

- More circular, with smooth, simple shoreline shorter shore length

Measured shore length of lake

Index of shoreline development of lake= ------------------------------------------------------------

Shore length of a circular lake with same area

Minimum index value = 1

Higher index value!increased shoreline development


4/25

Water budget: lake inputs and outputs

Residence time: amount of time water spends in lake (yr)= Lake volume/discharge rate

Discharge rate: rate of water output from lake (m3yr-1)

Flushing rate: rate of lake volume output (yr-1)= 1 / residence time

Lake parameters

6%+18% 12%

Lowest salinity,

nutrients,

productivity,

biodiversity

Highest salinity,

nutrients,

productivity,

biodiversity

Lake position (expressed as lake order)determines water input/output of lake

!influences chemical and biological characteristicsof lake

Seepage lakes: no surface inlets; ground water only (2, 1)

Drainage lakes: have surface outlets (1, 1, 2, 3)

Lake position in landscape


5/25

Vertical stratification in lakes: Thermal, oxygen, light,biological, primary production

Thermal stratification: vertical pattern of temperature differencesalong a depth gradient

Water column divided into layers that resist mixing above 4 deg C: warmer water floats on top of cooler water

below 4 deg C: cooler water floats on top of warmer water

at 4 deg C: max density water sinks to lake bottom

Mixingof the water column - breakdown of stratification Wind-driven

Ecologically important

Oxygenation of bottom waters

Replenish nutrients in surface waters

Stratified lakes - oxygenation/temp regulation of upper layers

Vertical temperature profile

Graph of lake depth vs temperature

Depth plotted on y axis (vertical)

More diagrammatic representation

Fundamental to limnological

understanding

Thermal stratification gives rise to

other forms of stratification

(chemical, light, biological)



6/25


Summer stratification Epilimnion

Warm, bright, less dense upper layer

Oxygen rich!higher concentration of fauna

Wind-driven mixing (within the layer)

Metalimnion

Transition zone

Includes thermocline where temperaturechanges most rapidly with depth

Hypolimnion

Cool, dark, denser lower layer Oxygen-poor!lower concentration of fauna

Winter stratification Very weak stratifiction

Reverse of summer

Cooler epilimnion

Warmer hypolimnion

Mixing prevented by ice cover

Isothermal lake Spring, autumn

No temperature change with depth

No layers

Mixed



7/25

Winter

- Ice cover

-Reverse of summer stratification

-

Cooler epilimnion floating on warmer hypolimnion

-Stratified lake

Autumn

-

Epilimnion cools

-Cool water sinks

-

Lake mixes

-

Breakdown of

stratification

!Isothermal lake

Summer

-

Epilimnion warms further, mixes

-Hypolimnion remains cool but is deeper,

i.e. thermocline descends

Annual pattern

on temperate

zone lake

Late spring

-Lake warms further

-Warmer epilimnion

floating on cooler

hypolimnion

!Stratified lake

Early spring

-

Ice melts-Lake warms slightly

-Lake mixes

!Isothermal lake

Factors affecting thermal stratification

Time of year, location: affect annual/daily variation inenvironmental temperature

Lake depth: shallow vs deep lakes

Fetch:

Uninterrupted distance travelled by wind across lake !mixing of lake

But correlated with depth !stratification intact!deeper mixing ofepilimnion only (rather than whole lake)!pushes hypolimniondeeper

Topography: geographic features shielding lake from wind

Solutes: increased density!resist mixing



8/25

Lake classification based on stratification/mixing patterns

Dimictic: biannual mixing (spring, autumn) and stratification (summer, winter)

Monomictic: annual mixing (autumn to spring) and stratification (summer only)

Amictic: no mixing

Polymictic: frequent, sometimes daily, mixing (afternoon through night) fromstorms and strong winds and stratification (mornings as sun rises) seen inmany shallow tropical lakes

Meromictic chemically stratified due to high solute concentration

Monimolimnion (dense, deep, non-mixing layer of salts)

Demarcated by pycnocline, depth with greatest density change (associated withchemocline- depth with most rapid [solute] change)

May stillbe thermally stratified above monimolimnion


Vertical oxygen profile

Vertical oxygen profileaffected by

Thermal stratification

Biological activity

Lake classification based on patterns of oxygenconcentration:

Orthograde

Spring, low production lakes, lower biological activity

Epilimnion (warmer, lower O2solubility) lower [O2]

Hypolimnion (cooler, higher O2solubility) higher [O2]

Clinograde

Summer, productive lakes, higher biological activity

Epilimnion (warmer, light, photosynthesis) higher [O2]

Hypolimnion (cooler, dark, decomposition) lower [O2]


9/25

Vertical oxygen profile

Heterograde

Just below thermocline!peak [O2] (oxygen anomaly)

Low production lakes!deep light penetration Growth of hypolimnion algae (Algal plate)

Vertical light profile

Euphotic zone Upper layer with sufficient light for net primary production by

algae

From surface (100% light penetration) to 1% surface light

penetration depth

Compensation zone Just enough light for photosynthesis to support algae only

Net primary production = 0

Aphotic zone Insufficient light for photosynthesis to support growth


10/25

Vertical light profile

Log

Light penetration Estimated using Secchi disk

Affected by:

Suspended particles (e.g.,phytoplankton, sediment)

Dissolved pigments (e.g.,tannins)

Depth/differentialabsorbance of colours(wavelengths) by water

Most strongly absorbed: IR,red, UV

Least absorbed: blue,green (most reflected)

Biological vertical profiles

Examples

Algae (phytoplankton) affected by light penetration

Bacteria and zoobenthos (bottom-dwelling

invertebrates) vertical profiles in the sediment

affected by [O2]

Zooplankton and fishes affected by physical (e.g.,

[O2]) and biological factors (e.g., predation)


11/25

Diel Vertical Migration (DVM)

Daily pattern observed in zooplankton (small pelagic

animals)

Diurnal migration to deeper waters avoid predation from

visual predators

Depth limited by [O2]

Nocturnal migration to shallow waters faster growth and

reproduction

Also observed in larval fishes

Biological vertical profiles

Primary production vertical profiles

Net primary production (NPP): Energy in lakeecosystem (from photosynthesis) excludingmetabolic requirements (for respiration) of algaeand plants

Highest NPP surface waters (epilimnion) inagricultural and urban watersheds

Higher temperature

High light

High inorganic nutrients


12/25


Lake classification based on primary production

Eutrophic lake: High 1 production

Nutrient-rich

Abundant phytoplankton

Poor light penetration!turbid water due to phytoplankton

Photic zone!upper epilimnion Oxygen depleted (anoxic) hypolimnion

Oligotrophic lake: Low 1 production

Nutrient-poor

Low in phytoplankton Good light penetration!clear water

Photic zone!epilimnion to hypolimnion

Well oxygenated hypolimnion


Lake classification based on primary production

Mesotrophic lake: Intermediate 1 production

Intermediate nutrient availability - between oligotrophic to eutrophicconditions

Dystrophic lake: Very low 1 production

Nutrient-poor abundant predacious plants

Low in phytoplankton

Low light penetration!dark water dissolved organic pigments

Oxygen depleted!anoxic hypolimnion


13/25

Lake types and origins

Glacial lakes

Glaciation - a major processat higher latitudes

Deposited sediments(glacial till)!moraines,alluvial dams

Deposited icebergs!kettle ponds

Depressions/basins plunge basins, glacialscouring, proglacial lakes


Non-glacial lakes Oxbow lakes(billabongs, bayous)

erosion/sedimentation along streammeanders

Sinkholes dissolved limestone in karst

areas

Frost polygons thawed permafrost

Beaver ponds biological activity


14/25


Crater lakes volcanicactivity

Rift lakes tectonicactivity along fault lines

Lake Pinatubo Lake Toba

Lake Baikal Lake Poso African Rift Lakes

Lakes types and origins

Inland, shallow wetlands

Coastal wetlands - part brackish

Tonle Sap

Chilka Lake

Lake Songkhla


15/25

Natural lakes in

tropical SE Asia- Inland, shallow wetlands

- Coastal wetlands: part brackish

- Volcanic and tectonic lakes

Tasik Bera (Malaysia)

Tonle Sap (Cambodia)

Inle Lake (Myanmar)

Lake Songkhla (Thailand)

Lake Toba (Sumatra)

Lake Poso (Sulawesi)

Lake Pinatubo (Luzon)

Lake development Lakes have finite life spans

Gradually become shallower

Lakes!wetlands

Key process: sedimentation particles dropped bymoving water

Inorganic sediment (e.g., clay,silt, sand, etc.) in drainage lakes

Basins often deeper thanwater depth

Lake Baikal: 1741m water +>3000m of sediment

Organic sediment (e.g., peat

compressed, very slowlydecomposing plant material)


16/25

Artificial Lakes

Reservoirs

Artificial pond or lake Created by construction of

a dam or barrage across a

Valley

Depression

River mouth

River basin

Morphology and hydrologydistinct from natural ponds

or lakes

Artificial Lakes

Reservoirs Often characterised by

dendriticshorelines

Different from natural lakes

TasikTemenggor


17/25

Swamps

Wetland

Soil saturated with

water

Shallow standing water

(up to 1m depth)

Extensively vegetated

Grasses marsh or bog

Trees - swamp

Tasik Chini

Okeefenokee

Swamps Lentic environment

Low-lying area relative to surrounding topography

Water table at or close to the surface; prone to flooding

Substratum includes spongy, slowly rotting vegetation

Extensive root mats and macrophytes

Regulates water flow and quality - functions like a giant,landscape level sponge

Absorbs and holds excess water during rainy periods flood control

Slow release of trapped water during dry period maintain water flow

Natural filter for polluted runoff traps/absorbs pollutants and nutrients

Important habitat

E.g., Singapores Nee Soon Swamp Forest


18/25

Lotic environments

Running or flowing waters(cf. lentic - standing waters)

Rivers

Streams (creek, crick, branch,rivulet, trace, brook )

Springs

Estuary

Stream parameters

Stream morphometrics Velocity: rate of downstream

movement

Gradient: decrease in elevationover fixed distance

Cross-sectional area ~0.5 x (greatest depth x width)

Discharge: volume of watercarried per unit time

Velocity x Cross-sectional area

High discharge:

Spates: Small pulses

Floods: major peaks


19/25

Stream order

Streams classified based on position in landscape

Assignment of stream order based on joining of two

streams of previous order

First Order:

permanent stream

originating from

ground water; no

other streams joining

Second Order:

Joining of two first

order streams

Third Order: Joining

of two second order

streams

Joining of a lower order

stream does not raise

the order of the stream

River Continuum Hypothesis

Low order streams

Heavily shaded; allochthonous input

coarse particulate organic matter (CPOM)e.g., falling leaves

Shredders(that break up CPOM) dominate

Intermediate order streams

More open; autochthonousinputaquatic algae and

plantsand allochthonous inputfine particulate organic

matter (FPOM)from upstream Scrapers/grazersand filter feeders/collectorsdominate

High order streams

Open; allochthonousinput

FPOM (photosynthesis

inhibited by turbid water)Filter feeders/collectors

dominate

Predicting downstream characteristics of temperatestreams


20/25

References Singapore freshwater habitats

Corner EJH, 1978. The Freshwater Swamp-forest of South Johore and Singapore. BotanicGardens, Parks and Recreation Department, Singapore. 266 pp.

Johnson DS, 1973. Freshwater life. p. 103-127. In: Chuang, S. H. (ed.).Animal Life and Nature inSingapore.Singapore University Press. xiv + 302 pp.

Lim KKP, Ng PKL, 1990.A Guide to the Freshwater Fishes of Singapore.Singapore Science

Centre, Singapore. 160 pp.

Ng PKL, 1991.A Guide to the Freshwater Life in Singapore. Singapore Science Centre,Singapore. 162 pp.

Ng PKL, Lim KKP, 1999. The diversity and conservation status of fishes in the nature reserves of

Singapore. Proceedings of the Nature Reserves Survey Seminar (1997). Gardens Bulletin,

Singapore, 49: 245265.

Tan HTW, Chou LM, Yeo DCJ, Ng PKL, 2010. The Natural Heritage of Singapore, 3rd Edition.

Pearson Prentice Hall. 323 pp.

Turner IM, Boo CM, Wong YK, Chew PT, Ibrahim A, 1996. Freshwater swamp forest in

Singapore, with particular reference to that found around the Nee Soon firing ranges. Gardens

Bulletin, Singapore,48: 129157.

Yeo DCJ, Wang LK, Lim KKP (eds.), 2010. Private Lives: An Expos of Singapores Freshwaters.

Raffles Museum of Biodiversity Research. 258 pp.

Ng PKL, Corlett RT, Tan HTW (eds.), 2011. Singapore Biodiversity: An Encyclopedia of the

Natural Environment and Sustainable Development. Editions Didier Millet.


Up to two-thirds or more of Singapores land area iswater catchment

Much of Singapores original freshwater habitats lost ormodified

High biodiversity - including rare and endangeredspecies

Singapores freshwater habitats can be broadly classifiedinto three categories: Natural

Urban (artificial or modified) Ephemeral


21/25

Classification of habitats in Singapore

Natural habitats

Tend to be refuges for native aquaticspecies

Tree-country forest streams (primary,secondary forest)

Freshwater swamp

Urban habitats (artificial of modified)

Artificial or modified ecosystems

Tend to have more exotic species Open-country rural streams

Concrete canals, drains

Reservoirs (inland, coastal)

Park/garden/landscape ponds

Ephemeral habitats

In natural areas, e.g., pools, temporarystreams in forests

In artificial areas, e.g., marshland?

Natural freshwater ecosystems

Rivers and streamsAbsence of large rivers

Original large natural freshwater ecosystems - small rivers e.g., Sungei Kranji, Sungei Seletar, Sungei Kallang, Singapore River

But now almost all drowned or heavily modified

Absence of native large river species


22/25


Forest streams

Primary/secondary rain-forests

Bukit Timah and Central Catchment NatureReserves

Mostly flowing into inland reservoirs

Few, if any, torrent streams

Natural/unmodified environmentalconditions

Shallow (


23/25


Nee Soon Swamp Forest (contd)

Natural/unmodified environmental conditions

Slow-flowing streams draining into shallow, oftenflooded, valleys

Saturated, waterlogged soils - unstable and anaerobicsubstratum

Plants with some similar adaptations to mangrove plants

stilt or prop roots

breathing roots (pneumatophores)

Clear, stained (by tannins from decaying vegetation),soft, acidic (typically 28 deg C

Little any leaf litter or woody debris

Algae and macrophytes

Different environmental conditions (cf.forest streams) Open, deeper, less acidic waters

Few robust, adaptable native aquaticspecies

More exotic species better adapted to

modified conditions. E.g.,

Small species

Species associated with higher pH andtemperature waters

Guppy (Poecilia reticulata)


24/25

Name that reservoir

Bedok

Jurong Lake

KranjiLower Peirce

Lower Seletar

MacRitchie

MarinaMurai

Pandan

Poyan

PunggolSarimbun

Serangoon

Tekong

TengehUpper Peirce

Upper Seletar

Artificial/modified freshwater ecosystems

Reservoirs

17 reservoirs for domestic/industrial use

Artificial equivalents of natural lentic habitats (i.e. lakes),which are absent

Damming natural river drainages or river basins Protected and Urban/Unprotected catchments

Inland reservoirs and coastal (estuarine) reservoirs

Inland reservoirs dams at headwaters/upper reaches

Coastal (estuarine) reservoirs barrages at river mouth or acrosscommon basin

Take years to flush out salt water


25/25

Artificial/modified freshwater ecosystems

Different environmental conditions (cf. foreststreams)

Open, deeper, less acidic, sluggish to standing waters

Few robust, adaptable native aquatic species

More exotic species better adapted to modified conditions.E.g.,

Large river/lentic species

Species associated with higher pH and temperature waters

Artificial/modified freshwater

ecosystems

Ponds Small, mostly isolated in parks, golf courses and

disused granite quarries

Canals

Heavily modified rivers/streams, especially thoseflowing through urban areas

Canalisation - straightening, deepening, widening,and cementing of the banks and substrates

Canalised for: Flood control

Mosquito control

Exposed to urban runoff and pollution

Harsh, exposed environmental conditions Warm, hard, often polluted, shallow waters

Bare concrete substratum

Frequent and severe flash flooding

Few robust, adaptable natives

More exotic species. E.g., Species associated with hard, high pH and temperature

waters

lecture 3 fw habitats_2 slides

Documents