 The study of fresh bodies of water  Lentic: standing water (lakes and ponds)  Lotic: flowing water (streams and rivers)

 How might they be different?

 Glacial erosion and deposition - movement of glaciers eroded land (Great Lakes)  Deposition and erosion of sediment in a meandering river creates an oxbow lake

 Geologic Activity- tectonic movement; rift valleys and volcanic craters fill with water  Manmade: dams, log jams, strip mining (all lakes in TX except one, which one???)

 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

 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)

 Enters the water by ◦ 1. absorption from the atmosphere ◦ 2. 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

 Water loses oxygen through ◦ increased temperature ◦ increased respiration of aquatic life ◦ 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

 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

 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

 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

 2. Limnetic Zone -Open water zone where photosynthesis occurs  Plankton- organism that cannot swim against a current ◦ Phytoplankton- photosynthetic plankton; algae ◦ Zooplankton- animal-like plankton; rotifer  Nekton-free swimming organisms

 Is carried out in the limnetic zone by phytoplankton (ALGAE) and in the littoral zone by macrophytes- large aquatic plants (emergents and submergents)  6CO 2 + 6H 2 O + light  C 6 H 12 O 6 + 6O 2 (photosynthetic equation)

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: 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: Trophogenic Zone, Tropholytic Zone, Compensation Level, Littoral Zone, Limnetic Zone Epilimnion, Metalimnion, Hypolimnion, Thermocline, Benthic Zone sun, sun rays, emergents, submergents, phytoplankton, fish. Label where decomposition and photosynthesis are occurring.

1. Rainwater runs off - dissolves and carries nutrients and sediment into lakes. 2. Water carries with it silt, clay, organic matter, and nutrients in solution to enrich the aquatic ecosystem 3. Human activities including road building, logging, mining, construction, and agriculture add to the amount of silt and organic matter

 Eutrophication- nutrient enrichment of an aquatic ecosystem  Oligotrophication- nutrient reduction in an aquatic ecosystem

 Deeper, steep sides  Poorly developed littoral zone  Clear blue water  High in DO  Poor in nutrients: phosphorous, nitrogen, and calcium  Few organisms but a high diversity  Very little organic matter

 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

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