Patterns in Aquatic Ecosystems

Shallow vs DeepFresh vs SaltSwift vs StagnantChanging vs ConstantEphemeral vs Permanent

Limnology vs Oceanography

Patterns of Aquatic Ecosystems

• Important Properties of Water• Types of Organisms• Freshwater Ecosystems • Marine Ecosystems• Transition Areas

Important Properties of Water

• High specific heat–Warms and cools slowly–Large amount of heat necessary to raise temperature

• Reaches max density at 4oC–Ice floats–Warm water above cold water

Properties of Water

• 800x more dense than air– Organisms still more dense

– Need buoyancy

Properties of Water

• More viscous than air– More energy to move through water

– Leads to streamlined shapes

Properties of water…• Light attenuates quickly– Photosynthesis only in shallow waters

Properties of Water

• Phosphorus and Nitrogen limiting nutrients

• Less oxygen than air– Enters at surface and via photosynthesis

– Cold water holds more• Carbon dioxide and

buffering

Properties of Water

• High surface tension– Can have organisms on surface

Types of Organisms

• Can classify based on mode of life/location

• Can classify based on trophic mode

Mode of life

• Benthos - attached or resting on bottom– Epifauna: live on bottom (crabs, scallops)

– Periphyton: attach to stems & leaves of rooted plants

– Infauna: buried in sediment (clams, worms)

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Mode of life

• Plankton– Floating, weak swimmers•Phytoplankton: photosynthesize

•Zooplankton: herbivores & carnivores

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Mode of life

• Nekton– Swimming organisms

– Go where they want

– Fish, squid, frogs, turtles, seals, octopus

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http://www.berkeley.edu/news/media/releases/2005/03/images/aculeatus_walk.mov

Mode of life

• Neuston– Rest or swim on surface

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Trophic Mode

• Decomposers– Many insects, bacteria

– Break down organic matter

– Bacteria, fungi

• Photsynthesizers (primary producers)– Derive energy from sunlight

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Trophic Mode

• Deposit feeders– Eat organic material on bottom

– Worms, some snails and clams

• Filter feeders– Remove food from water

– Clams, mussels, baleen whales… QuickTime™ and a

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Trophic Mode

• Grazers– Eat living plant material– Insects, sea urchins..

• Carnivores– Eat animals

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Types of Aquatic Ecosystems

• Freshwater • Marine• Transitions between land & sea

Freshwater Ecosystems• Lentic

– Standing water– Lakes, ponds, bogs

• Lotic– Running water– Streams, rivers

Lentic Zonation

• Limnetic: to depth of light penetration

• Profundal zone: beyond depth of light penetration– Usually absent in ponds

Lentic Zones

• Littoral zone– Shallow, light penetrates to bottom

– Rooted plants– High diversity– Subzones of vegetation

•Emergent, floating, submergent

Lentic Zonation

• Limnetic zone– Depth of effective light penetration - compensation point

– No benthos and few if any neuston

Lentic Zonation

• Profundal zone– Bottom and deep water region– Fewer plankton and no neuston– Absent in ponds

Physical Factors

• Transparency– Turbidity– Secchi Disk

• Alkalinity (buffering capacity)

Thermal Stratification

• Epilimnion: warm surface water• Metalimnion: 0C changes with depth

• Hypolimnion: cold deeper waters

• Changes with season

Thermal Stratification

Seasonal Changes

Stratification

• Temperate lakes - mixed twice/year– Brings oxygen to bottom, nutrients to top

• Tropical lakes– Low elevation:

• Warm water on top, doesn’t cool regularly• Poor to no mixing

– High elevation• Can stratify and mix daily

Lake Productivity

• Oligotrophic– Deep, sandy or gravel bottom

– Low nutrients– low plant growth

•low productivity

– Low decomp at bottom •oxygen not depleted

Lake Productivity

• Eutrophic– Shallow, muddy, nutrient rich

– High plant growth•high productivity

– Summer stratifies•no mixing

– Decomposition•depletes O2

Oligotrophic vs Eutrophic

Oligotrophic vs. Eutrophic

Times of Low Oxygen Interesting

• Dimictic vs. Meromictic lakes• Hypolimnion in the summer when no oxygen input– Productive lakes– Deep water fishery disappears

• Heavy Snow Cover– No algal photosynthesis

Dystrophic

Kettlehole bog