Eutrophication is the excess availability of nutrients needed for photosynthesis (1). Often times these excess nutrients are phosphorus and nitrogen from fertilizers, but could also be increased amounts of available sunlight or carbon dioxide (2). Eutrophication occurs naturally over many years, but is often sped up by human activities that dump phosphorus and nitrogen into aquatic ecosystems (1).
These excessive nutrients allow for rapid growth of algae, creating dense algal blooms (1). The large areas covered by algal blooms and then limit the amount of sunlight penetration and reduce the growth rate of underwater plants and can cause them to die off (1). Photosynthesis during eutrophication can also cause the deletion of dissolved inorganic carbon levels and raise pH levels to extreme highs (1). During times of eutrophication a thick blue-green layer of algae can be seen covering the top of a body of water (3).
Eventually the algal blooms will die off and during this process microbial decomposition severally depletes the dissolved oxygen concentration within the water (1). This creates anoxic, or dead zone, that lacks enough oxygen to support most organisms living in the body of water; causing fish and other wildlife to die off, sometimes in large quantities (1). Other consequences of eutrophication are degraded water quality and public heath risks (1).
One method to remediate eutrophication is to use constructed wetland systems. The two most efficient systems are vertical flow systems and horizontal flow systems (5). These systems can remove approximately 20-52% of nitrogen and 35-66% of phosphorous, the two main nutrients that can cause eutrophication when in excess (5). The constructed wetlands should contain plant species that thrive within the environment; the plants then require more nutrients and thus remove more from the eutrophic waters. Furthermore, even more nutrients can be collected and removed from the water by regularly harvesting and replanting the plant species within the constructed wetlands (5).
Another method of remediation is restoring macrophytes, aquatic plants, within shallow lakes (6). Different communities of macrophytes can be added to the shallow waters and quickly improve the transparency and turbidity of the lake waters (6). After flowing through the macrophytes the nutrients of the water can be reduced anywhere from 58-80% (6).
1. Chislock, M; Doster, E; Wilson, A; Zitomer,R. Eutrophication: Causes, Consequences, and Controls in Aquatic Ecosystems. Nature Education (2013). Accessed December 22, 2014.
2. Csaba, J; Csaba, P. Water Resources Management and Water Quality Protection. Accessed December 22, 2014. http://www.tankonyvtar.hu/hu/tartalom/tamop425/0032_vizkeszletgazdalkodas_es_vizminoseg/ch09s02.html
3. Leveille, W. Eutrophication in Aquatic Ecosystems. Accessed. December 22, 2014. http://wleveille.blogspot.com/2013/02/eutrophication-in-aquatic-ecosystems.html
4. River algae Sichuan. Accessed December 22, 2014. http://en.wikipedia.org/wiki/File:River_algae_Sichuan.jpg
5. Biswas, D; Jiang, G; Li, L; Li, Y; Nian, Y. Potential of constructed wetlands in treating the eutrophic water: Evidence from Taihu Lake of China. Bioresource Technology. 99 (2008). 1656–1663.
6. Chua, H; Li, X; Pu, P; Wang, G; Xia, M; Zhang, L. A Mosaic Community of Macrophytes for the Ecological Remediation of Eutrophic Shallow Lakes. Ecological Engineering. 35 (4). 582-590.