1. Aquatic Ecosystems Chapter 7

2. 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

3. Two types of aquatic ecosystems: 1. 1. Freshwater – lakes, ponds, rivers, streams, swamps, marshes, wetlands (limnology is the study of these) 2. 2. 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

4. Freshwater Ecosystems Rivers Ponds Lakes Swamps

5. 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

6. Origins of Lakes Where do lakes come from? Can you name some ways they are formed?

7. Rift lakes Caused by shifts in earth’s tectonic plates, forms very deep lakes Examples: deepest - Lake Baikal (Russia), 2 nd deepest - Lake Tanganyika (Africa’s rift valley)

8. Volcanoes Forms a depression called a caldera that fills with water Example: Crater Lake, Oregon

9. Glacier Action In mountainous areas, glaciers can leave series of basins that fill with water When mountains are near the sea, it can form deep fjords The Seven Rila Lakes, Bulgaria Geirangerfjord, Norway

10. Solution Lakes Formed in areas where soluble rock is dissolved by water, usually very circular, also called sinkholes

11. River action Oxbow Lakes – formed when river changes course and cuts off a small curved lake

12. Wind action Playa – Spanish word meaning “beach”, very shallow, ephemeral lakes that are only present after heavy rains Playas in Texas

13. Animals Beaver dam Beaver dam

14. Human Activity Wilson Dam and Reservoir, Alabama Hoover Dam and Lake Mead, Nevada and Arizona

15. What is the difference between a lake and a pond? SizeDepthInflow and outflow LakeslargerDeeperRivers and streams flow in/out PondssmallerMore shallow, sun reaches bottom throughout May not have any inflow or outflow

16. Habitats in Lakes and Ponds 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 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 Water strider Duckweed (Lemna gibba)

17. 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

18. 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)

19. Habitats in Lakes and Ponds Benthic zone – bottom of the lake or pond inhabited by decomposers, worms, insect larvae, clams, snails

20. 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

21. 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

22. Thermal stratification in lakes

23. World Rivers

24. Rivers Rivers begin at higher elevations with precipitation falling and forming small streams, called headwaters

25. Rivers Smaller streams (tributaries) gather into larger streams and rivers The floodplain of a river is the area adjacent to it that periodically floods, the river deposits sediment in the floodplain making it very fertile

26. Rivers Rivers flow down to a lake or ocean, where sediments can form a delta Mississippi River delta

28. Rivers The geographic area drained by a river is called a watershed

29. Rivers Important water quality characteristics for rivers include: Temperature Oxygen content Flow rate Nutrient/pollution content – nitrates and phosphates

30. 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 Headwaters of the Mississippi Mississippi River at New Orleans

31. Wetlands Areas covered with water at least part of the year

32. Wetlands Important functions of wetlands: 1. 1. Water purification 2. 2. Flood control 3. 3. Buffer coastlines from storms 4. 4. Spawning grounds for fish and shellfish 5. 5. Habitat for many plants and animals 6. 6. Recreation areas for people

33. 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

34. 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