Eutrophication Management Strategies: Nutrient Loading Restrictions |
Research: Impacts of Cultural Eutrophication on Lakes
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To curtail phosphorus runoff from fields and manure disposal sites, soil erosion rates have to be dramatically reduced. Agricultural practices that minimize runoff and reduce phosphorus applications to land surface via fertilizers should be enforced. For example, farmers can reduce erosion and sedimentation by 20-90% by applying better irrigation techniques to control the volume and flow rate of runoff water, improve water efficiency, keep soil in place, and reduce soil transport (Sharpley et al. 1994). Soil erosion can also be prevented or reduced by ending deforestation and burning techniques in farming. Governments should impose policies that give farmers incentives to decrease phosphorus use, such as removing subsidies that promote excessive fertilizer consumption. Additionally, re storing wetlands that act as buffers between fields and lakes is necessary to decrease runoff of excess nutrients (Jorgensen 2001).
These strategies have all been applied with success to improve eutrophic conditions in a variety of lakes. However, there are several drawbacks and complications to relying on nutrient loading restrictions. First, the process of treating the impacts of eutrophication by reducing nutrient levels is expensive, incurring costs of up to millions of dollars for an individual lake (Carpenter 2008). Lake Washington’s $140 million campaign to divert sewage effluent was the most costly pollution control effort of its time (Edmondson 1991). Second, similar nutrient loads do not have the same impact in different environments or at different points in time (Anderson et al. 2002). Removal of phosphorus entering lakes may be ineffective if there is already a large reservoir of nutrients stored in sediments previously released into the water. This shows the need to avoid nutrient loading into lakes as early as possible through proper management and planning practices.
Furthermore, nutrient loading restrictions are not fool proof. For instance, attempts to reduce nutrient inputs of erosion from agriculture have not worked as well as attempts to control point-source industrial wastewater pollution (Schindler 2006). Hence, certain restrictions that worked for a particular lake may not work for another, and optimum eutrophication control strategies will differ due to the existence of variable ecosystems (particularly the presence of agriculture). Third, while techniques to lower nutrient concentration can be effective in improving lake eutrophication, these approaches ignore the biological interactions of the lake responsible for internal nutrient recycling, poor water clarity, and the slow response to nutrient diversion. Such interactions between phytoplankton and algae contribute to eutrophication and cannot be mitigated by reducing nutrient inputs alone (Carpenter et al. 1995). Thus, it is necessary to develop an integrated approach incorporating bio manipulation to target the biological factors aggravating eutrophication unaffected by nutrient controls.
These strategies have all been applied with success to improve eutrophic conditions in a variety of lakes. However, there are several drawbacks and complications to relying on nutrient loading restrictions. First, the process of treating the impacts of eutrophication by reducing nutrient levels is expensive, incurring costs of up to millions of dollars for an individual lake (Carpenter 2008). Lake Washington’s $140 million campaign to divert sewage effluent was the most costly pollution control effort of its time (Edmondson 1991). Second, similar nutrient loads do not have the same impact in different environments or at different points in time (Anderson et al. 2002). Removal of phosphorus entering lakes may be ineffective if there is already a large reservoir of nutrients stored in sediments previously released into the water. This shows the need to avoid nutrient loading into lakes as early as possible through proper management and planning practices.
Furthermore, nutrient loading restrictions are not fool proof. For instance, attempts to reduce nutrient inputs of erosion from agriculture have not worked as well as attempts to control point-source industrial wastewater pollution (Schindler 2006). Hence, certain restrictions that worked for a particular lake may not work for another, and optimum eutrophication control strategies will differ due to the existence of variable ecosystems (particularly the presence of agriculture). Third, while techniques to lower nutrient concentration can be effective in improving lake eutrophication, these approaches ignore the biological interactions of the lake responsible for internal nutrient recycling, poor water clarity, and the slow response to nutrient diversion. Such interactions between phytoplankton and algae contribute to eutrophication and cannot be mitigated by reducing nutrient inputs alone (Carpenter et al. 1995). Thus, it is necessary to develop an integrated approach incorporating bio manipulation to target the biological factors aggravating eutrophication unaffected by nutrient controls.