Causes of Eutrophication and its Effects of on Aquatic Ecosystems

saturated oxygen caused by the death <strong>and</strong> decomposition <strong>of</strong> plants, subsequent fish kills, <strong>and</strong> loss<strong>of</strong> aquatic biodiversity. Additionally, blooms <strong>of</strong> algae known as red or brown tides carry toxinsthat are absorbed into animal tissues, such as shellfish, <strong>and</strong> may harm humans if ingested.Cyanobacteria also release neurotoxins that poison livestock <strong>and</strong> threaten humans (Carpenter et.al., 1998). The process <strong>of</strong> reversing eutophication is difficult due to the challenges in trackingpollution to <strong>its</strong> sources as well as the magnitude <strong>of</strong> the affected areas. However, thoughphosphorus has no documented negative effects on humans or animals, nitrate pollution is toxicat high concentrations, <strong>and</strong> can harm infants as well as cattle if levels reach 45 mg/L (Carpenteret. al., 1998). Because <strong>of</strong> this <strong>and</strong> other negative effects associated with eutrophication,numerous papers exist concerning the assessment <strong>and</strong> management <strong>of</strong> eutrophic aquaticecosystems. One such paper describes rating eutrophic levels based on concentrations <strong>of</strong> nitrate,as nitrogen is the most limiting nutrient for phytoplankton growth (Stefanous et. al., 2000).In this study we observed the process <strong>of</strong> eutrophication in a system <strong>of</strong> aquariums bytreating the submerged macrophyte <strong>of</strong> a species <strong>of</strong> Elodea that is common to temperate low-l<strong>and</strong>streams <strong>and</strong> lakes, with fertilizer run-<strong>of</strong>f applied to potted corn plants (Madsen <strong>and</strong> Baattrup-Pedersen, 1995). Our group conducted this experiment in order to better underst<strong>and</strong> the effects <strong>of</strong>fertilizer input <strong>and</strong> eutrophication on aquatic systems. We hypothesized that eutrophicationwould occur in tanks treated with fertilizer <strong>and</strong> that no significant evidence <strong>of</strong> eutrophicationwould occur in our control tanks. Based on our hypothesis we predicted that inputs <strong>of</strong> fertilizershould increase the growth <strong>of</strong> the Elodea plants in our experimental tanks, while the plants in ourcontrol tanks should have a significantly lower increase in growth. Additionally we predictedthat nitrogen, phosphorus, <strong>and</strong> ammonia concentrations as well as optical density <strong>of</strong> treated tanks2