‘Dead zones’ threaten oceans

Stuart Wakeham in the Atlanta Journal-Constitution: When you look in the waters of coastal Georgia and you see an ocean seemingly teeming with life, it is difficult to comprehend that large sections of the world’s oceans are considered “dead zones.” These are areas of the oceans where low levels of dissolved oxygen have either killed or driven off most of the fish and shellfish sought by commercial and recreational fishermen.

Oxygen-deprived areas of ocean have spread exponentially since the 1960s, affecting a total area of more than 95,000 square miles. Georgia’s waters may not be immune to the threat.

Natural and man-made processes cause dead zones. It begins when excessive loads of nutrients are introduced to the water from sewage, storm runoff containing fertilizer and other sources. These nutrients promote the growth of microscopic algae called phytoplankton. When phytoplankton die and decay, the process, if excessive, can consume much of the dissolved oxygen in the water, leading to an oxygen deficit (hypoxia).

…Although not considered a dead zone, Georgia’s coastal waterways are showing discouraging signs. Skidaway Institute scientist Peter Verity has monitored local water conditions for more than 20 years and documented a steady decline in dissolved oxygen; some areas approach hypoxic during the summer.

…Dead zones make up less than 2 percent of the world’s ocean volume. The model predicts that global warming could cause dead zones to grow by a factor of 10 or more by 2100….

The beach and boardwalk on Jekyll Island, a barrier island off the coast of Brunswick, Georgia. Shot by normanack, Wikimedia Commons via Flickr, under Creative Commons Attribution ShareAlike 2.0 License