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