Every year, an area of ocean around the size of New Jersey ‘dies’ at the mouth of the Mississippi. Now, new research has shown that the main culprit for the Gulf of Mexico’s dead zone is the farming industry.

It’s not news to many – we’ve already reported on how there is concern about water quality near farms which use a lot of fertilizers and pesticides, so it is little shock to discover that the fertilizers from corn and soy, and the animal waste from farms around the Mississippi, and in Indiana and Ohio along the Ohio river, are causing problems in their local rivers.

Dead zones in oceans are caused by very low levels of oxygen in the water, a condition termed hypoxia. The high levels of nitrogen and phosphorus in some fertilizers helps to cause hypoxic conditions. High levels of nitrogen and phosphorus also cause large algae blooms. When these algae die, they sink to the bottom of the ocean where bacteria start to decompose them. This decomposition process much of the oxygen in the surrounding water and leads to a dead zone where no marine life (save for a few species of jellyfish) can live because the oxygen levels are too low.

Fertilizers are not seen as a pollutant by the EPA therefore farmers are not required to regulate their release of it. Animal waste is however, and animal waste is supposed to be contained for 25 years before being released. Recent research has shown that phosphorous from manure is not just emanating from these containers of 25 year old manure – around a third of phosphorous pollution in rivers comes from pastured animals.

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