Increased survival of aquatic life through algal pretreatment of nitrate-contaminated runoff

Industrial discharges, agricultural runoff, and waste from livestock farms contain high concentrations of nitrates which contaminate groundwater, rivers, lakes, and oceans. Accumulation of nitrates in water bodies has been shown to have significant negative effects, from physiological harm to fish and invertebrates to ecosystem-level impacts and food web-wide effects. Elevated nitrate levels also contribute to harmful algal blooms and eutrophication, creating dead zones that further threaten aquatic life. Humans may develop several health complications such as methemoglobinemia in infants, increased risks of certain cancers, thyroid dysfunction, and other health problems from consuming aquatic animals with high levels of nitrate. This research explores methods for reducing the toxicity of nitrate on aquatic life. We hypothesized that treating nitrate-contaminated river water with algae (algal pretreatment) will reduce nitrate levels and allow fish introduced into the treated water to survive longer than they would in untreated water. We tested our hypothesis by adding a range of nitrate concentrations to river water, performing or withholding algal pretreatment, and then adding fish. We found that algal pretreatment extended fish survival by up to 50%, supporting the hypothesis that algal pretreatment can effectively mitigate the harmful effects of nitrate runoff on aquatic life. We believe the ability of algae to consume nitrate makes them an effective tool to protect aquatic life. Further studies are needed to confirm that the reduction in nitrate by algae was the cause of the increase in fish survival.