LSM3254_Lecture 3 FW Habitats

8/3/2019 LSM3254_Lecture 3 FW Habitats

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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

Freshwater habitats in Singapore

References:

Dodson, S. 2005.Introduction to Limnology. McGraw-Hill Chapters 2, 11

Watershed

Area of land that supplies water to a lake or stream

= Area of land drainedby a lake or stream

Also known as catchment ordrainage

Note: Surface watershed maynot correspond withgroundwater 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


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Lakes

Most of the worlds freshwater resides in a few large lakes

~60% of the worlds freshwater in three areas

Lake parameters

Lake morphometrics

Shape, area, volume Shore length (=perimeter)

Varies with shoreline development (human 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

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 (m3 yr-1)

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

Lake parameters

6%

Lowest salinity,

nutrients,

productivity,

biodiversity

Highest salinity,

nutrients,

productivity,

biodiversity

Waterru

nsdown

hill-accu

mulates

and

concentr

ates(by

evapora

tion)che

micals

Lake position determines water input/output of lake

influences chemical and biological characteristics of

lake

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

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

Lake position in landscape


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

Thermal stratification: vertical pattern of temperaturedifferences along a depth gradient

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

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

4 deg C: max density water sinks to lake bottom

Mixing of 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)



Summer stratification Epilimnion

Warm, bright, less dense upper layer

Oxygen rich higher concentration of fauna

Wind-driven mixing

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, less dense epilimnion

Warmer, denser hypolimnion Mixing prevented by ice cover

Isothermal lake Spring, autumn

No temperature change with depth

No layers

Mixed



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Heterograde

Just below thermocline peak[O2] (oxygen anomaly)

Low production lakes deep

light penetration

Growth of hypolimnion algae

(Algal plate)

Vertical oxygen profile Vertical light profile

Euphotic zone

Upper layer with sufficient light fornet primary production byalgae From surface (100% light penetration) to 1% surface light

penetration depth

Compensation zone Just enough light for photosynthesis to support algae

Net primary production = 0

Aphotic zone Insufficient light for photosynthesis to support growth

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)


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Diel Vertical Migration (DVM)

Daily pattern observed in zooplankton (small pelagicanimals)

Day migration to deeper waters avoid predation from visual

predators

Depth limited by [O2]

Night 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 lake

ecosystem (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

Primary production vertical profiles

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

Primary production vertical profiles

Lake classification based on primary production

Mesotrophic lake: Intermediate 1 production Intermediate nutrient availability - between oligotrophic toeutrophic conditions

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


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Lake types and origins

Glacial lakes Glaciation - a major process

at higher latitudes

Deposited sediments(glacial till) moraines,alluvial dams

Deposited icebergskettle ponds

Depressions/basins plunge basins, glacialscouring, proglacial lakes


Non-glacial lakes Oxbow lakes (billabongs, bayous)

erosion/sedimentation along streammeanders

Sinkholes dissolved limestone in karstareas

Frost polygons thawed permafrost

Beaver ponds biological activity


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

ChilkaLake

Lake Songkhla


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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)

Artificial Lakes

Reservoir

Artificial pond or lake

Created by construction of

a dam or barrage across a Valley

Depression

River mouth

River basin

Morphology and hydrology

distinct from natural ponds

or lakes

Artificial Lakes

Reservoirs Often characterised by

dendritic shorelines

Different from natural lakes

Tasik

Temenggor


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Swamps

Wetland

Soil saturated withwater

Shallow standing water

(up to 1m depth)

Extensively vegetated

Grasses marsh or bog

Trees - swamp

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

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 downstreammovement

Gradient: decrease inelevation over fixed distance

Cross-sectional area ~1.5 x (depth x width)

Discharge: volume of water

carried per unit time Spates: Small pulses Floods: major peaks


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Classification of habitats in Singapore

Natural habitats Tree-country forest streams (primary,

secondary forest)

Freshwater swamp

Tend to be refuges for native aquaticspecies

Urban habitats (artificial of modified) Open-country rural streams

Concrete canals, drains

Reservoirs (inland, coastal)

Park/garden/landscape ponds

Artificial or modified ecosystems

Tend to have more exotic species

Ephemeral habitats In natural areas, e.g., pools, temporary

streams in forests

In artificial areas, e.g., marshland?

Natural freshwater ecosystems

Rivers and streams Absence 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

Natural freshwater ecosystems Forest streams

Primary/secondary rain-forests Bukit Timah and Central Catchment Nature

Reserves

Mostly flowing into inland reservoirs

Few, if any, torrent streams

Natural/unmodified environmental conditions Shallow (


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Natural freshwater ecosystems

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 tomodified conditions. E.g.,

Small species Species associated with higher pH and

temperature waters

Guppy (Poecilia reticulata)

Name that reservoir

http://www.pub.gov.sg/water/Pages/LocalCatchment.aspx

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 across

common basin Take years to flush out salt water


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Artificial/modified freshwater ecosystems

Different environmental conditions (cf. forest

streams) 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 those

flowing 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

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LSM3254_Lecture 3 FW Habitats