ZOL 355 Lecture 12 Outline of Last Lecture II Reactions of the Nitrogen cycle continued a Ammonification b Nitrification c Dentrification d Review III Environmental issues with Nitrogen Outline of Current Lecture IV Earths water reservoirs V Lake formation a Karst b Oxbow VI Stratification VII Seasonal temperature Current Lecture I Earth s Water Reservoirs a Biome concept not appropriate for aquatic environments b Overview of Earth s aqueous reservoirs c Oceans d Freshwater II Lake Formation Classification a Glacially formed b Karst Lakes i result from the erosion of underlying rock c Fluvial lakes oxbow Lakes i Lakes formed from crustal plate movements III Stratification a Different zones or layers that result from differences in temperature density b Stratification results from density differences c Layers and their characteristics temp mixing light O2 i Epilimnion 1 Freely circulation light O2 photosynthesis IV V ii Metalimnion characterized by a thermocline iii Hypolimnion 1 does not influence the hypolimion 2 No circulation low O2 no photosynthesis Seasonal summer temperature profiles a During full summer stratification only the epilimnion can mix b Fall Overturn i Wind can help but density drives mixing ii Entire lake becomes oxygenated c Winter overturn i If no ice cover circulates light O2 cold so photosynthesis is minimal ii If ice no circulation low O2 d Spring Overturn i Wind drives mixing ii Entire lake becomes oxygenated Classification based on Trophic state a Eutrophic i High plant growth high primary production b Oligotrophic i Low plant growth low primary production
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