Patterns in Aquatic Ecosystems Shallow vs Deep Fresh

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 • 800 x 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 http: //www. berkeley. edu/news/media/releases/20 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