Environmental Problems, Their Causes, and Sustainability 1

SunlightGreenfrogPaintedturtleBlue-wingedtealPondsnailMuskratLittoral zoneLimnetic zoneDivingbeetleProfundal zonePlanktonBenthic zoneYellowperchBloodwormsNorthernpikeFigure 7-16 The distinct zones of life in a fairly deep temperate zone lake.SunlightSunlightLittleshorevegetationLimneticzoneProfundalzoneOligotrophic lakeLow concentration ofnutrients and planktonSparse fishpopulationNarrowlittoralzoneSteeplyslopingshorelinesSand, gravel,rock bottomMuchshorevegetationLimneticzoneProfundalzoneEutrophic lakeHigh concentration ofnutrients and planktonDense fishpopulationSilt, sand,clay bottomWidelittoralzoneGentlyslopingshorelinesFigure 7-17 An oligotrophic, or nutrient-poor, lake (left) and a eutrophic, or nutrient-rich, lake (right).Mesotrophic lakes fall between these two extremes of nutrient enrichment. Nutrient inputs from human activitiescan accelerate eutrophication and lead to algae blooms and fish die-offs. This can reduce the fish populationsshown for a europhic lake.plants grow and decompose to form bottom sediments.A lake with a large or excessive supply of nutrients(mostly nitrates and phosphates) needed byproducers is called a eutrophic (well-nourished) lake(Figure 7-17, right). Such lakes typically are shallowand have murky brown or green water with poor visibility.Because of their high levels of nutrients, theselakes have a high net primary productivity.http://biology.brookscole.com/miller14139