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17 January 2021

Nutrient pollution

The excess of nitrogen and phosphorus in the ocean

Photo Rosie Steggles @unsplash

This type of pollution is caused by the over enrichment of water with nitrogen and phosphorus, usually coming from land based activities such as agriculture, sewage, industrial run-off and fossil fuel combustion. A 2017 global water quality study has identified that human activities have doubled nitrogen concentrations and tripled phosphorus concentrations as compared to naturally existing levels in the ocean. 

As nitrogen and phosphorus are limiting nutrients in the ocean, they have the capacity to cause persisting coastal issues like eutrophication that lead to hypoxic conditions and harmful algal blooms. Eutrophication is the excessive and rapid growth of photosynthetic marine phytoplankton and algae, that lead to lower light conditions in the surface waters and massive deoxygenation events called “dead zones” that can persist without adequate mixing and reoxygenation of the water column. 

These oxygen minimum zones lead to permanent or seasonal collapse of entire ecosystems with large amounts of fish and coral die off. Harmful algal blooms (HABs) cause the above mentioned oxygen depletion, but also have the ability to be toxic to both humans and marine wildlife. Around 80 species of diatoms, dinoflagellates and cyanobacteria are known to produce hazardous toxins that are easily passed up the food chain when shellfish such as oysters, scallops, mussels and clams filter feed on the toxic organisms and cause various types of poisoning and even death upon consumption by humans. 

Whether you appreciate the intrinsic value, scientific value, biodiversity value, life support value or the economic value of the ocean, it is clear that without this body of water the human population would not exist on this planet or be in the prosperous state that we are today. 

We all depend heavily on the resources and life support the ocean provides, and we are dwelling further into the unknown by continuing to degrade ocean health. With the complex and interconnected problems facing our ocean, there is no question as to why we need more ocean science and exploration. We must expand our understanding of the ocean and establish baseline data for all essential ocean variables to understand the impacts we are having on the ocean, what we should do about it, and how to manage this most important resource in a more effective and sustainable manner.



Credits to Maja Krass – Bachelor Thesis World Bachelor in Business Program: “How Private Vessels Can Aid Marine Scientific Research”, April 2020  “Marine microbial community dynamics and responses to ….” 17 Jan. 2019,  “Ocean acidification due to increasing … – OceanRep – Geomar.”  “Ocean Acidification | Smithsonian Ocean.” 30 Apr. 2018, “Eutrophication and Hypoxia in Coastal Areas – World ….”  “Manual on harmful marine microalgae – UNESCO Digital Library.”


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Ocean biodiversity

How the ocean produces oxygen

Coral Bleaching



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