Freshwater Ecosystems Notes

1. Freshwater Ecosystems Notes

2. Limnology • The study of fresh bodies of water • Lentic: standing water (lakes and ponds) • Lotic: flowing water (streams and rivers)

3. Lenticvs Lotic • How might they be different?

5. Formation of lakes and ponds: • Glacial erosion and deposition - movement of glaciers eroded land (Great Lakes) • Deposition of silt, driftwood, and other debris in slow-flowing streams- cuts off a meander and forms a crescent shape or oxbow lake.

6. Formation of lakes cont. • Shifts in the Earth’s crust- tectonic movement; valleys and craters fill with water • Nongeological activity: manmade dams, log jams, strip mining (all lakes in TX except one, which one???)

7. Physical Characteristics • High specific heat of water make aquatic environment temperatures more stable than terrestrial Epilimnion: Metalimnion: Thermocline: Hypolimnion:

8. Physical Characteristics • High specific heat of water make aquatic environment temperatures more stable than terrestrial Epilimnion: surface water Metalimnion: middle Thermocline: Hypolimnion: deep cold layer

9. Physical Characteristics • High specific heat of water make aquatic environment temperatures more stable than terrestrial Epilimnion: surface water, small temperature change Metalimnion: middle mass of water with a rapid temperature decline (1°C/ meter) Thermocline: temperature gradient found in metalimnion Hypolimnion: deep cold layer cutoff from air; most dense

11. Seasonal Fluctuations • Summer- large thermocline. Why? • Winter- Surface water loses heat to atmosphere therefore thermocline decreases • Overturn: surface water temp. decreases and causes water to mix and stir up nutrients and dissolved oxygen because of density changes (Fall and Spring)

15. Dissolved Oxygen (D.O.) • Enters the water by absorption from the atmosphereand by photosynthesis • The amount of oxygen and other gases water can hold depends upon pressure and temperature • As temperature increases- solubility of dissolved oxygen decreases • As pressure increase- solubility of DO increases

16. Water loses oxygen through increased temperature, increased respiration of aquatic life, and aerobic decomposition • During the summer, oxygen may become stratified in lakes and ponds • The quantity of oxygen decreases with depth because of decomposition in the bottom sediments

17. During Spring and Fall overturn- water circulation (churning) replenishes oxygen in the bottom • In winter- DO decreases slightly with depth; DO is more stable because cold water can hold more DO than warm water

20. Sunlight • The depth to which light penetrates is limited by turbidity of the water and the absorption of light rays Trophogenic zone- layer through which light can penetrate and where photosynthesis occurs (photic zone) Tropholytic zone- layer through which light cannot pass through and where decomposition occurs Compensation level-where photosynthesis ends and decomposition begins

21. Trophogenic Zone: separated into two zones • 1. Littoral zone- (horizontal) shallow water zone where light penetrates the bottom emergents- plants whose roots are underwater and stems and leaves are above water. Live in the littoral zone. submergents-completely below water

23. 2. Limnetic Zone -Open water zone where photosynthesis occurs • Plankton- suspended/floating organism • Phytoplankton- photosynthetic plankton; algae • Zooplankton- animal-like plankton; rotifer • Nekton-free swimming organisms

26. Primary Production • Is carried out in the limnetic zone by phytoplankton (ALGAE) and in the littoral zone by macrophytes- large aquatic plants (emergents and submergents) • 6CO2 + 6H2O + light  C6H12O6 + 6O2 (photosynthetic equation)

27. Drawing: Lentic Ecosystem in mid-summer 1)Title your paper Lentic Ecosystem- mid-summer 2) Draw a cross section of a lake on your paper (this should take up a considerable amount of room on your paper). 3) Use your Freshwater Ecosystem Notes and laptop to label following on the cross section of a lake: Littoral Zone, Limnetic Zone, Trophogenic Zone, Tropholytic Zone, Compensation Depth, Epilimnion, Metalimnion, Hypolimnion, Thermocline, Benthic Zone, Profundal Zone 4) Use your freshwater Ecosystem Notes and laptop and draw in examples in their proper places of the following the cross section of a lake: sun, sun rays, emergents, submergents, algae, and fish. Label where decomposition and photosynthesis are occurring.

28. Nutrients • Rainwater runs off - dissolves and carries nutrients into lakes. • Water carries with it silt, clay, organic matter, and nutrients in solution to enrich the aquatic ecosystem • Human activities including road building, logging, mining, construction, and agriculture add to the amount of silt and organic matter

31. Nutrient status cont. • Eutrophication- nutrient enrichment of an aquatic ecosystem • Oligotrophication- nutrient poor aquatic ecosystem

32. Oligotrophic System • Deeper, steep sides • Poorly developed littoral zone • Blue-green water, clear • High in DO • Poor in phosphorous, nitrogen, and calcium • Few organisms but a high diversity • Very little organic matter

33. Oligotrophic

34. Eutrophic Systems • Shallow • Rich in organic matter and nutrients • DO depletion in hypolimnion during summer due to decomposition • Eventually will turn into a bog or marsh • Lots of organisms, low diversity

35. Eutrophic

36. EutrophicvsOligotrophic

37. For a healthy ecosystem you want a balance between eutrophic and oligotrophic. • There needs to be enough nutrients for organisms to grow and reproduce.

38. LoticEcosystems • Flowing Water Habitats • Creeks, streams, and rivers • The flow of the water influences the lives of the organisms inhabiting the waters and the physical characteristics of the stream.

39. http://www.scienceclarified.com/landforms/images/ueol_03_img0108.jpghttp://www.scienceclarified.com/landforms/images/ueol_03_img0108.jpg

40. How a Stream/ River Begins • Headwaters: streams that join together and form a river • Near headwaters river usually flow fast and currents are swift • Rocky bottom • Higher levels of D.O. due to flow and temperature of the water.

41. Middle of a River • Velocity decreases • River gets wider and wider • Meanders become common (curves) • Pools: where water is deeper and slows down, filled with fine sediments • Riffles: faster, shallower with rocky bottom • Run: fast flowing water, deeper water

42. How a Meander Forms

43. The meandering Tigre River, Argentina . PHOTOGRAPH REPRODUCED BY PERMISSION OF THE CORBIS CORPORATION Read more: http://www.scienceclarified.com/landforms/Ocean-Basins-to-Volcanoes/Stream-and-River.html#ixzz1147UMeyX

44. http://www.geographyhigh.connectfree.co.uk/s3riversgeoghigh26f.gifhttp://www.geographyhigh.connectfree.co.uk/s3riversgeoghigh26f.gif

45. http://belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/Meander_processes.jpghttp://belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/Meander_processes.jpg

46. Flood Plains • Flat stretches of land on either side of a slow moving river • During storms, rivers overflow and flood these areas • When water recedes deposits of rich sediment are left behind ; fertile land

47. Slower Water • Less oxygen • Warmer temperature • Communities of catfish, algae, turtles, dragonflies and other organisms that can live in lower DO.

48. Mouth • Usually empties into an ocean or a lake. • Water slows even more • Sediment is deposited and creates new land called a delta. • Where a river meets an ocean, freshwater mixes with salt water, an estuary is formed. • Estuaries are important nurseries for lots of aquatic organisms.

50. http://farm3.static.flickr.com/2117/2279411722_17c2675fb1.jpghttp://farm3.static.flickr.com/2117/2279411722_17c2675fb1.jpg