Chapter 7
Aquatic Ecosystems
Environmental ScienceSpring 2011
Chapter 7.1
Freshwater Ecosystems
Aquatic Ecosystems
• Types of organisms determined by salinity– Salinity: amount of dissolved salts in water
• Divided into freshwater and marine Banff National Park Hawaii
Aquatic Ecosystems
• Temperature, sunlight, oxygen, nutrients all play a role in where organisms live
Aquatic Ecosystems
• Organisms that live in aquatic ecosystems are grouped by their location and adaptations
1.Plankton: cannot swim against currents; driftersA. Phytoplakton: drifting plants, food base for most
aquatic organisms, majority are microscopic
Aquatic Ecosystems
1. Plankton:A. Zooplankton: drifting animals, may be
microscopic or as large as a jellyfish
Aquatic Ecosystems
2. Nekton: free swimming organism such as fish, turtles, and whales
3. Benthos: bottom dwelling organisms, many live attached to hard surfaces– Ex. Muscles, worms,
barnacles
Lakes and Ponds• Littoral Zone: nutrient rich, near the shore,
aquatic life diverse and abundant • Plants: – Cattails and reeds rooted in mud underwater,
upper leaves and stem emerge from water – Lilies are plants that have floating leaves
Lakes and Ponds
• Further from shore, no rooted plants• Phytoplankton here make own food from
photosynthesis
Lakes and Ponds• Some lakes have areas
so deep that there is too little light for photosynthesis
• Bacteria and other decomposers live on dead plants and animals that drift down from above
• Fish adapted to cold water can live here as well
Lakes and Ponds
• Benthic Zone: bottom of pond or lake• Inhabited by decomposers, insect larvae, and
clams
Lakes and Ponds
• Animals have adaptations to help them get what they need to survive
Lakes and Ponds
• Eutrophication: increase in the amount of nutrients in an aquatic ecosystem
• Eutrophic lake: lake with large amount of algae and plant growth due to nutrients– Less oxygen due to decomposition – Kills organisms needing oxygen – Runoff accelerates eutrophication
Lakes and Ponds
Freshwater Wetlands
• Freshwater wetlands: areas of land that are covered with freshwater for at least part of the year – Marshes – Swamps
Freshwater Wetlands
• Marshes: contain nonwoody plants– Cattails, etc.
Freshwater Wetlands
• Swamps: dominated by woody plants– Trees, shrubs, etc.
Freshwater Wetlands
• Wetlands perform several important environmental functions
• Act as filters, remove pollutants from the water
• Improve water quality, control flooding (absorb extra water)
• Fish use wetlands for spawning• Vegetation traps carbon
Freshwater Wetlands: Marshes
• Most located in Southeast • Florida Everglades: largest
freshwater wetland • Tend to occur on low, flat
lands and have little water movement
Freshwater Wetlands: Marshes
• Benthic zone in marshes: nutrient rich and contain plants, numerous types of decomposers, and scavengers
• Marshes attract many migratory birds
Freshwater Wetlands: Marshes
• Salinity: varies– Some slightly salty (brackish) water– Others salty as ocean water
• Organisms adapted to range of salinity
Freshwater Wetlands: Swamps
• Swamps: occur on flat, poorly drained land, often near streams
• Species depend on salinity of water and climate of area
Human Impact on Wetlands
• Wetlands previously thought of as wastelands that provide breeding ground for disease carrying insects
• Many have been drained and filled• Important role of wetlands as purifiers of
wastewater and flood protection • Vital habitats for wildlife
Rivers• Headwaters: cold and full of oxygen, runs
swiftly though a shallow riverbed• Normally originates from snowmelt in
mountains, as flows down mountain becomes warmer, wider, and slower containing more vegetation and less oxygen
Rivers
• Life in a River– Plants and animals are adapted to different areas
of the river