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
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