Eutrophication Management Strategies:
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Research: Impacts of Cultural Eutrophication on Lakes
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Bio manipulation refers to procedures that alter the food web—communities of organisms where there are interrelated food chains. In one form, bio manipulation prompts organisms to favour grazing on phytoplankton. In another, bio manipulation eliminates fish species that recycle nutrients and favour those that assist algal management (Shapiro et al. 1984). This latter method is new to the lake management community, which has relied mostly on nutrient loading restrictions to control eutrophication. However, due to its effectiveness, lower cost, and absence of machinery or toxic chemicals, it is becoming increasingly popular (Shapiro 1990).
Bio manipulation involves eliminating certain fish species or restructuring the fish community to favour the dominance of piscivorous fish instead of planktivorous fish. Food webs are controlled by resource limitation (“bottom-up”) and by predation (“top down”) methods. With “bottom-up” control, sources of energy that affect the dynamics of an ecosystem, such as solar energy and nutrient inputs, are controlled to limit the amount of algal production. Nevertheless, within the limits of “bottom-up” controls, there is still a necessity for “top-down” pressures to reduce the abundance of phytoplankton by increasing the numbers of zooplankton and fish that graze on them (Shapiro et al. 1984).
While bio manipulation may not be effective on its own, particularly in larger lakes where changes in fish population have less of an impact, research has shown that bio manipulation used in tandem with other nutrient reduction and control mechanisms can be fully effective in a variety of lakes (Lammens 2001). Hence, it is necessary to use nutrient loading restrictions and bio manipulation in conjunction to control and limit all sources of eutrophication, speeding up the recovery of a lake.
Bio manipulation involves eliminating certain fish species or restructuring the fish community to favour the dominance of piscivorous fish instead of planktivorous fish. Food webs are controlled by resource limitation (“bottom-up”) and by predation (“top down”) methods. With “bottom-up” control, sources of energy that affect the dynamics of an ecosystem, such as solar energy and nutrient inputs, are controlled to limit the amount of algal production. Nevertheless, within the limits of “bottom-up” controls, there is still a necessity for “top-down” pressures to reduce the abundance of phytoplankton by increasing the numbers of zooplankton and fish that graze on them (Shapiro et al. 1984).
While bio manipulation may not be effective on its own, particularly in larger lakes where changes in fish population have less of an impact, research has shown that bio manipulation used in tandem with other nutrient reduction and control mechanisms can be fully effective in a variety of lakes (Lammens 2001). Hence, it is necessary to use nutrient loading restrictions and bio manipulation in conjunction to control and limit all sources of eutrophication, speeding up the recovery of a lake.