Ocean “dead zones” expanding rapidly

A rapid increase in oxygen-free “dead zones” is making coastal fish stocks more vulnerable to collapse and putting coastal ecosystems from the Gulf of Mexico to the Baltic Sea at risk, scientists reported on Monday.

“Dead zones” are found in areas where algae suck the oxygen from the water, feeding on fertilisers washed from fields, sewage, animal wastes and pollutants from the burning of fossil fuels.

A study published in the US journal Proceedings of the National Academy of Sciences found that the number of hypoxic (low oxygen) zones is growing globally at a rate of 5% a year, endangering the food supply of hundreds of millions of people who depend on coastal fisheries.

Higher air temperatures may aggravate the problem of “dead zones” because oxygen dissolves less readily in warmer water.

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