Lecture 09

1. Lecture 09 Limnology - study of inland waters Ecology of Freshwater Ecosystems: Rivers, streams, lakes and wetlands

2. Three basic types of freshwater ecosystems: • Lotic: rapidly-moving water, for example streams and rivers. • Lentic: slow-moving water, including pools, ponds, and lakes. • Wetlands: areas where the soil is saturated or inundated for at least part of the time.

3. Loctic: Rivers and Streams Rivers and streams can be divided along three dimensions: Length: Pools + runs Width : Wetted / active channels Vertical: Water surface, column Riparian zone is a transition area between the aquatic and upland terrestrial environments.

4. Rivers and Streams River basin – area of land drained by river drainage network Separated by watersheds

5. Dimensions of Stream Structure

6. Flow Rate • Variation a Function of: • vegetation/nature of surrounding landscape • Forests ‘damp out’ variation in flow • Seasonal variation in ppt. • Rainy/dry season climate • Seasonal snow melt • Impact on flooding • Flood pulse concept: health of river system depends on maintaining natural variations in flow

7. River Continuum Concept Organic matter from vegetation adjacent to stream in headwaters provides nutrient base coarse particulate organic matter CPOM  FPOM: provides nutrient base for food web in low reaches of river See: http://www.cotf.edu/ete/modules/waterq/wqcontinuum.html for more

9. 4 Invert Feeding groups: • Feeding on bacteria in organic matter of various sizes: • Shredders: breakdown CPOM: consume bacteria • Filtering and gathering collector: feed on bacteria found in FPOM • Grazers: feed on algae on surfaces • Gougers: burrow into submerged logs/wood debris

11. Lakes Low spot – captures and retains water Formation involves geologic processes + dam building by humans Most FW resides in lakes. 20% in Great Lakes of North America

12. Many Types of Lakes - + 11 types Glacial lakes Tectonic Lakes Landslide lakes Volcanic lakes Shoreline lakes

13. Littoral zone: Shallows – light reaches bottom Limnetic zone: open waters – Habitat of zooplankton and nekton (free-swimming organisms) Benthic: primary place of decomposition

14. Light Lake color depends on light absorption and biological activity Light is increasingly attenuated with water depth Temperature Lakes become thermally stratified as they warm. Temperatures vary seasonally with depth Water Movement Wind-driven and temperature mixing of the water column is ecologically important. Oxygen can be limiting Eutrophic vs. oligotrophic lakes

15. Seasonal Temperature Changes

17. Nutrients and Lakes: Oligotrophic: Low nutrient availability Low surface area to volume ratio Low biological production well oxygenated May have high species diversity Generally older lakes Eutrophic: High biological production High nutrient availability – particularly N and K High surface area to volume ratio may be depleted of oxygen – benthos anaerobic  methane production Dystrophic: Acidic, high in organic matter

18. From Schoenherr A.A. 1992. A Natural History of California. University of California Press..

19. Lakes - Human Influences Human populations have had profound, usually negative effect. Municipal and agricultural run-off  eutrophication. Exotic species - Zebra Mussels  alter ecology

20. Dams Major dam builders Humans Beaver Damming interrupts both nutrient spiraling and the river continuum Downstream flow is greatly reduced but a constant inflow is maintained The resulting lake develops a heavy bloom of phytoplankton (or floating plants) due to high nutrient levels of decaying material on the newly flooded land Disrupts seasonal fluctuations in flow Lentic-adapted fish (many introduced exotics) replace lotic-adapted fish Pulsed releases of water (hydroelectric dams) can wipe out or dislodge downstream organisms Generally water released from hypolimnon is cold and low in O2

21. Succession Accumulated sediment  wet meadow Nutrients from outside lake  eutrophication

22. Freshwater wetlands (25.6) = terrestrial wetlands • 6% of Earth’s surface – declining • Importance – various reasons • Various types/degree of wetness • permanently flooded to periodically saturated soil • Hydrophytic plants • Obligate wetland plants require saturated soils • Facultative wetland plants can grow in either saturated or upland soil • Occasional wetland plants are usually found out of wetland environments but can tolerate wetlands

30. 25.6 Freshwater Wetlands Are a Diverse Group of Ecosystems • Wetlands occur in three topographic situations • Basin wetlands develop in shallow basins, from upland depressions to filled-in lakes and ponds–water flow is vertical • Riverine wetlands develop along shallow and periodically flooded banks of rivers–water flow is unidirectional • Fringe wetlands occur along the coasts of large lakes–water flow is in two directions

36. Reduced Oxygen Levels and Wetlands as Biological Filters decreased breakdown of organic matter Wetlands = nutrient sinks Nutrient sink = environment that traps nutrients Nutrient source = net release of nutrients – results as oxygen is introduced Biological filter: remove potentially damaging chemicals from waterways

37. Hydrologic Regulators Act as hydrologic buffers Water amounts entering may vary Excess water absorbed and retained Water amount leaving remains constant Impact: Water may percolate into aquifers Prevent down stream flooding Prevent damage Reduce leaching of nutrients

38. Ecological Issues: The Continuing Decline of Wetlands • The loss of wetlands has reached a point where both environmental and socioeconomic values are in jeopardy • Waterfowl habitat • Groundwater supply and quality • Floodwater storage • Sediment trapping

41. Wetland Protection Endangered Species Act Clean Water Act of 1972 – section 404 EPA State Laws California Coastal Commission Other: http://ceres.ca.gov/wetlands/introduction/defining_wetlands.html http://biology.kenyon.edu/fennessy/AMN%20Wetland%20Webpage/Comps%20Webpage/thebroadperspective.htm