MADRID — The International Union for Conservation of Nature (IUCN), warns that climate change and nutrient pollution are depleting the oceans of oxygen in a report published in December.

The report states that nitrogen and phosphorus runoffs from sewage, agricultural waste and industrial pollution are the main cause of oxygen deletion, especially in coastal seas.

According to the BBC, the study also found that climate change is heating the oceans and reducing the amount of oxygen they can hold.

The study found the oxygen dissolved in the ocean has dropped two percent globally and as much as 40 percent in parts of the tropics.

The study warns that the combined effects of warmer oceans and run offs could affect the top 1,000 meter of the water column, which is richest in biodiversity.

The IUCN states that deoxygenation harms bigger fish that are oxygen sensitive, such as tuna, marlin and sharks, but favors microbes and jellyfish that are not.

The report suggests that the lack of oxygen would force the fish to live closer to the surface, where they are vulnerable to overfishing.