Drought in the Midwest contributed to what has been measured as the fourth smallest 'dead zone' in the Gulf of Mexico since 1985, according to scientists with the Louisiana Universities Marine Consortium and the National Oceanic and Atmospheric Administration.
This year's dead zone measures about 2,889 square miles compared with a dead zone of 6,770 square miles last year.
The size of the dead zone can fluctuate based on river flow, amount of nutrients in the water and if any storms pass through mixing higher oxygen waters with lower oxygen waters.
The dead zone is a low-oxygen area that forms off the coast of Louisiana every summer when nutrients from agriculture and urban runoff flow down the Mississippi River into the Gulf.
These nutrients feed microscopic organisms that use up oxygen when they die and decompose on the water bottom.