Patterns in Aquatic Ecosystems Shallow vs Deep Fresh vs Salt Swift vs Stagnant Changing vs Constant Ephemeral 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 4 o C –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)

Mode of life Plankton –Floating, weak swimmers Phytoplankton: photosynthesize Zooplankton: herbivores & carnivores

Mode of life Nekton –Swimming organisms –Go where they want –Fish, squid, frogs, turtles, seals, octopus 05/03/images/aculeatus_walk.mov

Mode of life Neuston –Rest or swim on surface

Trophic Mode Decomposers –Many insects, bacteria –Break down organic matter –Bacteria, fungi Photsynthesizers (primary producers) –Derive energy from sunlight

Trophic Mode Deposit feeders –Eat organic material on bottom –Worms, some snails and clams Filter feeders –Remove food from water –Clams, mussels, baleen whales…

Trophic Mode Grazers –Eat living plant material –Insects, sea urchins.. Carnivores –Eat animals

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: 0 C 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 O 2

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