Have you ever encountered a green water body with an abundance of algae floating on the surface? That is a significant symptom of eutrophication. An increasing number of lakes and water bodies look like this globally, including some of our most crucial bodies of water.
What is Eutrophication?
Eutrophication is a process by which excess nutrients such as phosphorus (P) and nitrogen (N) deposit into a body of water and become concentrated in particular areas. This process disturbs natural systems and often causes adverse effects. While eutrophication is a natural process in aging lakes, human activities accelerate this process in younger waters by depositing excess nutrients (Castro & Freitas, 2010). Some human activities that drive this process include population growth; urbanization; industrial expansion; agricultural pollution; water supply development; and changes in land use.
These areas of high nutrients often experience accelerated algae growth, resulting in algae blooms. These blooms disturb the aesthetic nature of the water bodies and impact water oxygen levels. As these algae blooms begin to spread, they quickly take in the oxygen from the water, decreasing oxygen levels. With lower oxygen levels, the fish populations become trapped in hypoxic (deficient levels of oxygen) waters leading to their mortality, also known as fish kills. These hypoxic areas in the waterbody are also called dead zones. These dead zones are areas where the eutrophication process is causing such low oxygen levels that nothing can survive in these areas.
In addition to causing biodiversity loss, eutrophication also impacts human health and the economy. This process reduces water quality, causing it to become undrinkable. Some toxins are irritants, and some are suspected to be carcinogens. The fish in these lakes can also become inedible and sometimes toxic, thus affecting the livelihoods of the local communities.
Eutrophication and Climate Change
Climate change has also had a hand in accelerating eutrophication. Changes in climates and temperatures impact the natural cycle and processes of water bodies, leading to “significant changes in the physical structure and the biological configuration of the waters.” Eutrophication processes often thrive in warmer, nutrient-rich areas with prolonged ice-free seasons. So as climate change prevails, the warmer season lengthens in places with colder winters, such as Canada. As the warmer periods in a year extend, so does the growing period for these plants and toxins.
A Case Study of Lake Erie
Lake Erie is the world’s eleventh-largest lake in terms of surface area and is situated on the international boundary between Canada and the United States. It “supplies drinking water to 11 million [people, contains] 50% of the fish found in all of the Great Lakes combined,” and is home to numerous aquatic species.
It is the southernmost, warmest, and shallowest of the Great Lakes, making it the perfect breeding ground for eutrophication. Because of this, eutrophication is nothing new to Lake Erie, as concerns began in the 1960s and 1970s when increased phosphorus inputs from various human activities resulted in a notable degradation in water quality. In response, in 1972, phosphorus abatement programs were initiated as part of the Great Lakes Water Quality Agreement, which had quick success in Erie and reigned till 1987. But the declaration of the ‘restoration’ of Lake Erie quickly reversed, and algae populations have continued to increase and affect the lake since the mid-1990s and have caused excessive oxygen depletion.
The current eutrophication of Lake Erie threatens all the services provided by this lake. Consequently, gaining a handle on this issue will not only help sustain the services currently offered by the lake but will also enhance the potential for future services.
Solutions to Eutrophication
As part of any remediation project, further research into reliable indicators of eutrophication and direct indicators of the sources of these nutrients is necessary to manage these ecosystems.
Understanding which nutrients is essential for mitigation is also crucial to successful management. Research has concluded a unanimous agreement that reducing phosphorus inputs will directly benefit eutrophication reduction. However, there is a gap in research about nitrogen’s role in eutrophication, as reducing nitrogen alone will not aid mitigation. Research into reducing phosphorus and nitrogen inputs together is still needed before understanding the optimal course-of-action.
There are many innovative approaches to solving eutrophication. An example of a solution to the source of of the issue is vertical farming. Vertical farming is an excellent alternative to intensive agriculture with less input of nutrients. Vertical farming is a closed system that does not deposit nutrients into earth systems.
Another innovative solution to eutrophication is duckweed. Duckweed can be used as a remediation for the aftermath of he process. Duckweed is a plant that has taken nutrients used in agricultural practices and provides oxygen back into the water source. The use of duckweed has the potential to reverse the adverse effects of eutrophication and restore natural ecosystems.
Canada has begun their remediation process for Lake Erie. It recognized the eutrophication of the lake as an ecological risk. Their action plan was published in February 2018 and will start in 2023, with revision every five years after. The plan outlines the importance; their actions to achieve phosphorus reduction targets; their efforts to improve policies; and areas needing more research.
Canada, E. and C. C. (2018, March 13). Government of Canada. Canada.ca. Retrieved December 8, 2022, from https://www.canada.ca/en/environment-climate-change/services/great-lakes-protection/action-plan-reduce-phosphorus-lake-erie.html
Castro, P., & Freitas, H. (2010). Linking anthropogenic activities and eutrophication in estuaries: The need of reliable indicators. Eutrophication: Causes, Consequences and Control, 265–284. https://doi.org/10.1007/978-90-481-9625-8_13
Dokulil, M. T., & Teubner, K. (2010). Eutrophication and climate change: Present situation and future scenarios. Eutrophication: Causes, Consequences and Control, 1–16. https://doi.org/10.1007/978-90-481-9625-8_1
Kane, D. D., Conroy, J. D., Richards, R. P., Baker, D. B., & Culver, D. A. (2014). Re-eutrophication of Lake Erie: Correlations between tributary nutrient loads and phytoplankton biomass. Journal of Great Lakes Research, 40(3), 496-501. Retrieved from: [PDF] researchgate.net
Landesman, L., Fedler, C., & Duan, R. (2010). Plant nutrient phytoremediation using duckweed. Eutrophication: Causes, Consequences and Control, 341–354. https://doi.org/10.1007/978-90-481-9625-8_17
Sayer, C.D., Davidson, T.A., Rawcliffe, R. et al. Consequences of Fish Kills for Long-Term Trophic Structure in Shallow Lakes: Implications for Theory and Restoration. Ecosystems 19, 1289–1309 (2016). https://doi.org/10.1007/s10021-016-0005-z
Scavia, D., Allan, J. D., Arend, K. K., Bartell, S., Beletsky, D., Bosch, N. S., … & Zhou, Y. (2014). Assessing and addressing the re-eutrophication of Lake Erie: Central basin hypoxia. Journal of Great Lakes Research, 40(2), 226-246. Retrieved from: Assessing and addressing the re-eutrophication of Lake Erie: Central basin hypoxia – ScienceDirect
Watson, S. B., Miller, C., Arhonditsis, G., Boyer, G. L., Carmichael, W., Charlton, M. N., … & Wilhelm, S. W. (2016). The re-eutrophication of Lake Erie: Harmful algal blooms and hypoxia. Harmful algae, 56, 44-66. Retrieved from: https://ciglr.seas.umich.edu/wp-content/uploads/2017/09/Watson_etal.pdf.pdf
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