Molles: Ecology 2 nd Ed. Lakes Most of worlds freshwater resides in a few large lakes: Great Lakes contain 20% of freshwater in world Molles: Ecology 2 nd Ed. Fig 3.37 Structure: Littoral Zone: Shallows Limnetic Zone: Open lake Molles: Ecology 2 nd Ed. Fig 3.37 Lakes Vertical Distribution: Epilimnion: warm surface layers Metalimnion: (Thermocline) temp changes substantially with depth Hypolimnion: cold dark waters Molles: Ecology 2 nd Ed. Lakes Color: Depends on light absorption and bio. activity Stratification: Become thermally stratified as they warm Molles: Ecology 2 nd Ed. Fig 3.38 Molles: Ecology 2 nd Ed. Temperate lake Molles: Ecology 2 nd Ed. Lakes Nutrient Levels Nutrient Levels Oligotrophic: low biological production, often well oxygenated Eutrophic: high biological production, may be depleted of oxygen Molles: Ecology 2 nd Ed. Oligotrophic lake = nutrient poor Little plant growth, deeper Molles: Ecology 2 nd Ed. Eutrophic lake = nutrient rich high plant growth, shallow Molles: Ecology 2 nd Ed. Mesotrophic lakes: some plant growth Life cycle of a glacial natural lake Lake forms from glacial deposits or groundwater filling hole = oligotrophic Molles: Ecology 2 nd Ed. Nutrients wash in from surrounding watershed, lake fills in some = mesotrophic Life cycle of a natural lake Molles: Ecology 2 nd Ed. Lake fills in further, nutrients wash in from surrounding watershed, heavy plant growth = eutrophic Finally lake fills in completely Life cycle of a natural lake Molles: Ecology 2 nd Ed. Lakes Human Populations have had profound, usually negative effects Municipal and Agricultural Run-off Eutrophic from nutrients Toxins Exotic Species Zebra Mussels, round goby Molles: Ecology 2 nd Ed. Index of Biotic Integrity IBI score is method to evaluate streams Compare biota to nearby undisturbed stream Fish communities generally used Molles: Ecology 2 nd Ed. IBI 1. Number of species, kinds, tolerances 2. Trophic compositions of species Omnivores Insectivores Piscivores 3. Fish abundance and condition Molles: Ecology 2 nd Ed. Fish IBI Eastern Corn Belt Scoring Classification Metric135 Total Number of Species< > 13 Number of Darter/Madtom/Sculpin Species % Headwater Species< Number of Minnow Species< Number of Sensitive Species< > 10 % Tolerant Individuals< 25 %25 50 %> 50 % % Omnivore Individuals 1 < 25 %25 50 %> 50 % % Insectivore Individuals 1 > 50 %25 50 %< 25 % % Pioneer Species Individuals 1 < 25 %25 50 %> 50 % Catch per Unit Effort< 300> 300 % Simple Lithophil Individuals> 40 %20 40 %< 20 % % DELT Individuals 1 < 0.1 %0.1 1.3 %> 1.3 % Molles: Ecology 2 nd Ed. East Fork Honey Creek 14 July 2009Actual ObservationIBI Score (no.) 1. Total number of Species61 2. Number of Darter/Madtom/Sculpin Species01 3. Headwaters sp. % of Total Number of Minnow Species01 5. Number of Sensitive Species01 6. % Tolerant Individuals % Omnivore Individuals05 8. % Insectivore Individuals01 9. % Pioneer Species Individuals CPUE % Simple Lithophil Individuals % DELT Total IBI18 Molles: Ecology 2 nd Ed. Summary Hydrologic Cycle exchanges water among different holding areas. Biology of aquatic largely determined by physical and chemical factors. Light, temp, salinity, oxygen, etc. Molles: Ecology 2 nd Ed.