BIOGRAPHY OF A RIVER

9-12 THEAGING OF LAKESOBJECTIVESThe student will do the following:1. Determine the trophic condition of a local body of water.2. Demonstrate the use of a Secchi disc.SUBJECTS:Science (Chemistry,Biology, Ecology)TIME:several field trips3. Test for pH, nitrogen, phosphorus, temperature, and dissolved oxygenin a body of water.BACKGROUND INFORMATIONLake eutrophication is the increase over time of nitrogen, phosphorus, and othernutrients necessary for production of algae and other plants. It is an importantpart of the process by which lakes pass from their original nutrient-poorMATERIALS:water analysis kitSecchi discvolunteer “lake watch”groupboat?wader?(oligotrophic) condition to a more productive (eutrophic) condition to become shallower with sedimentationand smaller with encroachment of marsh until, over geologic ages, lake basins are returned to land andterrestrial life. This “aging” process is called succession.Humans speed up the lake aging process by discharging nutrients from sewage treatment plants, fertilizedfields and pastures, and sediment from road, home, and commercial construction.Nutrients can be bad for a lake if excessive enrichment causes an algal bloom. This abundance of algaeeventually produces a large amount of decomposing organic matter, which depletes oxygen from the water.This can kill fish. The most productive fishing lakes have a moderate nutrient content that produces abalanced amount of algae and phytoplankton as fish food.The study of lake conditions is called limnology and involves water testing to evaluate nutrient content,temperature, pH, dissolved oxygen (DO), profiles with depth, light penetration, and other tests that maybe specific to a given location.Terms3-26