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Eutrophication and You

Jacob Greenlee

Everyone loves the beautiful colors of large bodies of water, especially if it is a glimmering emerald green – but not if it’s caused by eutrophication. Large swathes of green, brown, and even red algae can coat bodies of water in a suffocating blanket that chokes the life from organisms below. These large swathes of algae, known as Harmful Algal Blooms (HABs), pose a significant threat to the environment as they contaminate the meager 1% of freshwater available to humans. By understanding eutrophication and why it is a threat, steps can be taken to preserve the environment and our health.

More specifically, eutrophication is the process through which excessive levels of algae grow due to an excessive intake of necessary nutrients, such as phosphorus and nitrogen. These nutrients are among what are known as limiting factors, factors like sunlight, carbon dioxide, and nutrients found in fertilizers that determine how much of a population can grow. When limiting factors become more plentiful in the environment, the extent to which algae populations can grow also increases. Essentially, eutrophication is exacerbated by the unregulated use of products–like fertilizers–that contain limiting factors such as phosphorus and nitrogen for agricultural practices which leads to runoff into lakes. for example, over 50% of phosphorus used for agriculture ends up in our waterways.

Eutrophication has a variety of negative effects on the environment and poses a threat to all organisms that live in or near contaminated areas. The most significant consequence of eutrophication is the creation of hypoxic conditions, the presence of very little oxygen. As algae populations rapidly bloom across the surface of water, they block out sunlight, killing plants below the surface of the water along with animals who feed on them. In addition, when the algae die, they sink to the bottom along with all of their dead biomass, rapidly consuming oxygen through decomposition and further killing more organisms. Decomposing organisms also produce carbon dioxide, lowering the pH of bodies of water and leading to the acidification of water bodies – where more organisms die to acidic conditions. Around sixty-five percent of estuaries and coastal waters in the US are affected by excessive nutrient input, leading to large-scale consequences like mass poisoning and the death of wildlife, significant losses to aquaculture industries, reduced water quality in homes and facilities, public health risks, which all result in a loss of 2.2 billion dollars in the US annually for corrective measures.

Thankfully, there are several ways to combat eutrophication and protect the environment. One way is to introduce bivalve mollusk populations, which naturally filter – and remove – nutrients from the water. This tactic can also save money by reducing the same amount of nutrients a $470 million dollar investment in traditional practice can. Additionally, using satellite imagery to monitor and predict which waterways are at risk of eutrophication can allow preventive measures to be quickly made. Finally, biomanipulation – altering food webs to restore ecosystem health – pollution control, and monitored agriculture could help prevent the growth of algae.


  1. “Why we need to fix the world's freshwater algae problem” World Economic Forum.

  2. “What is eutrophication?” National Ocean Service.

  3. “Eutrophication: Causes, Consequences, and Controls in Aquatic Ecosystems”

  4. “Eutrophication” Brittanica.

  5. Picture Source:


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