Harmful Impacts of Eutrophication Case Study

Description and Causes

Fundamentally, eutrophication is a common freshwater and coastal marine eco-system phenomenon that is marked increased supply rate of organic matter, which consequently causes excessive algal and plant growth (Schindler,2006). Naturally, it is caused by ageing of the water body as the number of sediments gradually increases over centuries. However, the natural rate of eutrophication can be amplified by human activities or commonly known as cultural eutrophication. Many studies have established a strong correlation between nutrient concentrations in rivers and streams with human land use, especially in the 20th century. According to Howarth et al. (1996), the urban and agricultural activities in the watersheds have induced a nitrogen and phosphorous nutrients flux consequently causing the cultural eutrophication.

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Regardless of nature of the cause, nutrient enrichment occurs through both point and non-point sources. In the point sources, the nutrients are introduced into an aquatic system through wastewater effluents from both industries and municipals, in addition to stormwater discharge. Nonpoint sources, on the other hand, include agricultural fertilizers, livestock wastes, construction sites, abandoned mines and urban runoff (Carpenter et al.,1998).

Harmful impacts of Eutrophication

The greatest direct disruption due to eutrophication is felt in the aquatic ecosystem. As a result of increased nutrient supply, the waterbodies experience explosive growth of phytoplankton and algal blooms. Consequently, the process of dissolving oxygen is greatly inhibited and this results in oxygen depletion which ultimately causes the death of both animal and plant species in the aquatic zones.

To human life, the upsurge of the highly toxic algal blooms adversely promotes anaerobic conditions which extensively deteriorates the quality of water hence reduced availability of drinking water. For instance, the Wuxi town of about 2 million population went for more than a week without piped drinking water because of the severe algal blooms attack on Lake Taihu in 2007 (Duan et al., 2009). In addition to endangering fishing activities, the anaerobic conditions resulting from eutrophication increases chances of cyanobacteria which are extremely toxic to both humans and animals even in small concentrations (Blaha & Marsalek,2009).

Mitigation Measures

Laws and Initiatives

To against the deteriorating state of surface waters due to eutrophication, states across the globe have passed laws accompanied by regulating bodies to implement them. These laws centrally aim at controlling the water quality through regulation of point source nutrient levels. For instance, in the United States, the overall law regulating the quality of water is the Clean Water Act. This Act is regulated by EPA, which has specifically established a numeric nutrient threshold that should be adhered during effluent discharges. Chapter NR 217 of EPA's Winscon Legislature gives the standards and limitations to regulate the amount phosphorus nutrient introduced into surface water hence overall regulation of eutrophication. At the international level, the Agenda 21 further requires that the United Nations member countries should review, strengthen and restructure their existing institutions to enhance their efficiency in the management of water-related activities (De,1992).

Owing to the critical state of the surface water, several initiatives and programs have been established to help in reduction of nutrient pollution. For example, the National Oceanic and Atmospheric Administration (NOAA) through it North Fisheries Center and National Center for Coastal Ocean Science have identified Oyster as an efficient nutrient reduction fish species. Accordingly, they have resumed on a campaign to encourage the fishing communities and regulators in Connecticut and across the nation to embrace shellfish aquaculture which has been found to provide $ 8.5 to $ 23 million worth of nutrient reduction benefits (NOAA,2018).

Current state and recommendation

In a study carried out by Anderson et al. (2015) to examine spatial and temporal trends of eutrophication in Baltic Sea, there has been a remarkable reduction of nutrients pollution over the last two decades. This is a clear indication of the efficacy of the current collaboration efforts in monitoring and maintenance of high international standards regarding effluent quality. However, although management of eutrophication is a complex issue, the collective efforts of citizens, the policy makers and scientific community will further reciprocate to improved trends in curbing this pollution.

References

Andersen, J. H., Carstensen, J., Conley, D. J., Dromph, K., FlemingLehtinen, V., Gustafsson, B. G., ... & Murray, C. (2017). Longterm temporal and spatial trends in eutrophication status of the Baltic Sea. Biological Reviews, 92(1), 135-149.

Blaha, L., Babica, P., & Marsalek, B. (2009). Toxins produced in cyanobacterial water blooms-toxicity and risks. Interdisciplinary toxicology, 2(2), 36-41.

Carpenter, S. R., Caraco, N. F., Correll, D. L., Howarth, R. W., Sharpley, A. N., & Smith, V. H. (1998). Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological applications, 8(3), 559-568.

De, J. R. (1992). United Nations Conference on Environment & Development Rio de Janerio, Brazil, 3 to 14 June 1992. Reproduction, 351(10.1007).

Duan, H., Ma, R., Xu, X., Kong, F., Zhang, S., Kong, W., ... & Shang, L. (2009). Two-decade reconstruction of algal blooms in China's Lake Taihu. Environmental Science & Technology, 43(10), 3522-3528.

Howarth, R. W., Billen, G., Swaney, D., Townsend, A., Jaworski, N., Lajtha, K., ... & Berendse, F. (1996). Regional nitrogen budgets and riverine N & P fluxes for the drainages to the North Atlantic Ocean: Natural and human influences. In Nitrogen cycling in the North Atlantic Ocean and its watersheds (pp. 75-139). Springer, Dordrecht.

NOAA.(2018).What is eutrophication?. Retrieved from https://oceanservice.noaa.gov/facts/eutrophication.html

Schindler, D. W. (2006). Recent advances in the understanding and management of eutrophication. Limnology and oceanography, 51(1part2), 356-363.