Scientists predict that the Gulf of Mexico may have a record-setting dead zone this year. The low end of the estimate is a zone the size of Connecticut, Rhode Island and the District of Columbia combined. The high end of the estimate is a zone the size of New Jersey. (Does anyone else see the irony/joke in that?) The large dead zone prediction stems from the flood conditions in the Mississippi River watershed this year, which transported more-than-usual excess nutrients to the Gulf. This shows us once again that the oceans and coasts are intricately linked to what happens upstream, in inland watersheds that are far from the coast, and effective management needs to consider these linkages.
QUICK SCIENCE ASIDE: A “dead zone” occurs when the oxygen level in the water is extremely low (called hypoxic) or absent altogether (called anoxic) and can not support life in waters near the bottom. Fish, crabs, oysters, clams, or anything else living in that water either leaves (if it can) or dies. Dead zones can cause massive fish kills, like the one shown at right.
Dead zones occur when excess nutrient pollution enters the water, causing a cascade of biological activity that sucks up the oxygen. This excess pollution comes from us, humans, from fertilizer, agriculture runoff, storm water, industrial waste, or any other source that contains high levels of nutrients (the main culprits being phosphorus and nitrogen). Regulations over the past several decades have tried to curb the amount of nutrients entering our waterways, but huge dead zones still occur.