Parts of the world’s oceans are running low on oxygen, a new study finds. Fertilizers and other chemical pollutants in river runoff fuel blooms of algae that cause oxygen levels to dip precipitously when they die. A review of research into these so-called ‘dead zones,’ detailed in the Aug. 15 issue of the journal Science, finds that the number of dead zones has roughly doubled every decade since the 1960’s. The study authors, Robert Diaz of the Virginia Institute of Marine Science and Rutger Rosenberg of the University of Gothenburg in Sweden, tallied 405 dead zones in coastal waters worldwide today, affecting about 95,000 square miles (245,000 square kilometers) of ocean, an area about the size of New Zealand. While that may seem small compared to the total coverage of the oceans, the local effects can be devastating to marine ecosystems. These dead zones occur when fertilizer runoff dumps excess nutrients, such as nitrogen and phosphorous, into coastal waters, providing food for algae. When these microscopic plants die and sink to the ocean bottom, bacteria feed on them and subsequently consume all the oxygen dissolved in the water. This leaves fish and other bottom-dwelling sea […]