The price tag

4.8 to 12.7 million metric tonnes of plastic enter the ocean each year (Jambeck et al., 2015). Recent studies suggest that the annual socio-economic costs of ocean plastics pollution are as high as US$ 2.5 trillion. While clearly plastics pollution represents a major challenge, there are other ocean pollutants that also require urgent action.

Not quite as visible and widely talked about as plastic but with comparable impacts, nitrogen is also a major ocean pollutant, the scale of which is around the same as plastics at about 10 million metric tons of anthropogenic nitrogen entering the ocean each year, mainly from land-based sources including untreated or insufficiently treated wastewater, and fertilizer and manure run-off from farms (UNDP - Nitrogen – ocean plastics pollution’s forgotten neighbour).

Nitrogen, as well as phosphorous, are key nutrients found in aquatic ecosystems. When an excess amount of these nutrients is released, this results in coastal eutrophication, which leads to coastal dead zones or hypoxic (low oxygen) areas in the ocean. It already accounts for about 500 dead zones, covering more than 245,000 km² globally, equivalent to the surface of the United Kingdom. Most marine life cannot survive in such dead zones, resulting in the collapse of some ecosystems.

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