Aquatic Ecosystems Chapter 25 Classification of systems Aquatic systems classified by physical environment Salinity most important Marine divided broadly into coastal and open water Freshwater divided into lotic (flowing water ) and lentic (non-flowing water) All aquatic ecosystems are linked hydrologically Lakes Inland depressions containing standing water Ponds are shallow enough to have rooted vegetation in the center Can be formed by many processes, physical and biological Glacial activity Geologic movement River flow Beaver dams 1
Lake habitats Light important in lake ecosystems Temperatures vary Seasonally With depth Oxygen levels vary Seasonally With depth Lake zonation Compensation depth Lakes are divided into vertical and horizontal zones Vertical zones determined by light Compensation point important 2
Life in lakes Most life in littoral zone Inputs organic matter into the system Fish are flattened to navigate vegetation Periphyton Benthic algal growth is abundance in littoral zone Also called aufwuchs Limnetic zone Dominated by zooplankton and phytoplankton Spring bloom after turnover Nekton Fish move to preferred habitat Bass in surface waters (warm water species) Lake trout in deep waters (cold water species) 3
Profundal zone Eutrophication Dependent on rain of organic material for energy Oxygen is limiting Benthic area is anaerobic Process of adding nutrients to an ecosystem Natural waters vary in their level of eutrophication from oligotrophic to eutrophic Depends on character of local ecosystems, geology, etc. Have a high surface to volume ratio N & P stimulate algal growth Low oxygen in bottom sediments and deeper lake Eutrophic lakes Have low surface to water volume ratio Clear and blue Phosphorus is limiting Oxygen remains high in hypolimnion Bottom sediments are inorganic primarily Species diversity is high Oligotrophic lakes Measuring light penetration Carlson s Trophic State Index (TSI) 4
Dystrophic lake 2 inches below surface Receive humic materials from surrounding landscape Rivers are dynamic Fast flowing and steep in some areas Slow flowing and flat in others Fast streams are 50 cm/s Small particles washed away Slower waters drop sediment Streams are classified into orders Single streams are first order When they join, it becomes second order Increases in order when a stream of the same order joins it 5
Pools Decomposition Riffles Production On a smaller scale Life in moving habitats Adaptations for life in currents Streamlined Adhesive ability Fast water species Slow water species Invertebrate feeding guilds Shredders Break down coarse particulate organic matter (CPOM) 6
Invertebrate feeding guilds Filtering collectors or gathering collectors Eat fine particulate organic matter (FPOM) and associated bacteria Invertebrate feeding guilds Grazers Blackfly larvae Invertebrate feeding guilds Gougers Invertebrate feeding guilds Predators Continuum of environments Measuring stream flow 7
Estuaries Semi-enclosed water body where freshwater joins saltwater Varying currents and salinities Counterflow of waters of different salinities and temperatures creates a nutrient trap Nutrient trap Chesapeake Bay Nutrients and oxygen carried into estuary by tides and circulate within estuary 8
Benthic sessile organisms Striped bass (Morone saxatilis) Shad Croaker Anadromous fish SAV Ocean ecosystems Large (70% of earth s surface) Deep ( to 10 km) Lit surface area is small proportion of ocean environment Ocean stratified into benthic and pelagic Pelagic is stratified into neritic and oceanic 9
Ocean stratification Absorb nutrients directly from water Phytoplankton Zooplankton Zooplankton migration Smallest plankton Most are cyanobacteria Includes haptophyte Coccolithophores Nanoplankton Microbial loop 10
Nekton Benthic habitat Hydrothermal vents Coral reefs Cnidarians Coral reef organisms 11
Coral reef distribution Fringing reef Barrier reef Atoll Ocean productivity Highest productivity in coastal areas Productivity limited to regions of light and nutrients Re-distribution controlled by Turnover Upwelling 12
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