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Aquatic Ecosystems Chapter 7. Aquatic ecosystems have the same things going on as terrestrial ecosystems, just under water: photosynthesis (must be in upper levels of water) communities food chains and food webs predator-prey interactions diversity decomposition
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Aquatic ecosystems have the same things going on as terrestrial ecosystems, just under water: photosynthesis (must be in upper levels of water) communities food chains and food webs predator-prey interactions diversity decomposition cycling of nutrients (carbon, oxygen, nitrogen, phosphorus) succession
Two types of aquatic ecosystems: • Freshwater – lakes, ponds, rivers, streams, swamps, marshes, wetlands (limnology is the study of these) • Marine ecosystems – estuaries, salt marshes, mangroves swamps, coral reefs, oceans (marine biology and oceanography) What is the difference? Salinity – the amount of dissolved salts in the water
Freshwater Ecosystems Ponds Rivers Lakes Swamps
Lakes World’s deepest lake: Lake Baikal, Russia (1620 m or 5371 ft. deep) – holds 20% of the world’s freshwater World’s largest freshwater lake (area): Lake Superior (83,300 sq. km), one of the U.S. Great Lakes World’s largest salty lake: Caspian Sea (about 1/3 as salty as the ocean), 371,000 sq. km, southeast Europe/southwest Asia World’s highest altitude lake: Lake Titicaca (12,507 ft.), border of Bolivia and Peru
Important Lakes of the World See handout for the list of lakes you need to learn.
Origins of Lakes Where do lakes come from? Can you name some ways they are formed?
Rift lakes Caused by shifts in earth’s tectonic plates, forms very deep lakes Examples: deepest - Lake Baikal (Russia), 2nd deepest - Lake Tanganyika (Africa’s rift valley)
Volcanoes • Forms a depression called a caldera that fills with water • Example: Crater Lake, Oregon
Glacier Action The Seven Rila Lakes, Bulgaria • In mountainous areas, glaciers can leave series of basins that fill with water • When mountains are near the sea, it can form deep fjords Geirangerfjord, Norway
Solution Lakes • Formed in areas where soluble rock is dissolved by water, usually very circular, also called sinkholes
River action • Oxbow Lakes – formed when river changes course and cuts off a small curved lake
Wind action • Playa – Spanish word meaning “beach”, very shallow, ephemeral lakes that are only present after heavy rains Playas in Texas
Animals • Beaver dam
Human Activity Hoover Dam and Lake Mead, Nevada and Arizona Wilson Dam and Reservoir, Alabama
Habitats in Lakes and Ponds Duckweed (Lemna gibba) Water strider Surface film – due to the chemical nature of water; water molecules are attracted to each other forming a film over the surface of the water that can support small objects, such as insects and floating plants
Habitats in Lakes and Ponds Littoral zone – • extends out as far as rooted plants can grow (therefore stops where the water is too deep to allow light to penetrate for photosynthesis) • area of greatest diversity of both plant and animal life
Habitats in Lakes and Ponds Limnetic zone or open water- • fewer living things can survive in this plant-free zone • inhabited by tiny free-floating plankton large swimming animals (nekton)
Habitats in Lakes and Ponds Benthic zone – • bottom of the lake or pond • inhabited by decomposers, worms, insect larvae, clams, snails
Categories of plants in lakes and ponds • Emergent vegetation – such as cattails • Floating vegetation – such as water lily (rooted on bottom) and duckweed (not attached to bottom) • Submerged vegetation – such as coontail
Thermal stratification in lakes • Water has different densities at different temperatures; it is most dense at 4°C • In summer, warmer waters are at the surface due to the sun’s energy and cooler waters are at the bottom of lakes • In winter, surface waters may drop below freezing and turn to ice while deeper waters do not freeze; this allows fish to survive even when lakes freeze over
World Rivers See handout for the list of rivers you need to learn.
Rivers • Flow from headwaters at higher elevation, picking up volume from tributaries, flow down to a lake or ocean, where sediments can form a delta Mississippi River delta
Rivers Important water quality characteristics for rivers include: Temperature Oxygen content Flow rate Nutrient/pollution content – nitrates and phosphates
Rivers Water quality changes down the river: • Headwaters are colder, have more oxygen, are faster flowing • Further downstream, water is warmer, contains less oxygen, slower moving Mississippi River at New Orleans Headwaters of the Mississippi
Wetlands • Areas covered with water at least part of the year
Wetlands • Important functions of wetlands: • Water purification • Flood control • Buffer coastlines from storms • Spawning grounds for fish and shellfish • Habitat for many plants and animals • Recreation areas for people
Two main categories of wetlands: 1. Marshes Found on low, flat land Non-woody plants: reeds, rushes, cattails Benthic zones are very rich in nutrients Supports much wildlife, important to migratory waterfowl Ex: Everglades
Two main categories of wetlands: 2. Swamps Occur in flat, poorly draining areas Dominated by woody species, including cypress trees in the southern U.S. Supports much wildlife, including amphibians, birds, reptiles and fish
