Smithsonian flags ‘ dead zones’ that threaten coral reefs
Low- oxygen areas choke off marine life
Dead zones affect dozens of coral reefs around the world and threaten hundreds more, according to a study by Smithsonian Institution scientists released Monday.
This is the first study to find such a link, said lead author Andrew Altieri of the Smithsonian Tropical Research Institute in Panama.
After seeing a massive coral reef dieoff on the Caribbean coast of Panama in September 2010, Altieri and his team suspected it was caused by a dead zone — a low- oxygen area that kills marine life — rather than by warm or acidic ocean water, both of which are wellknown causes of coral die- offs.
“Ocean warming and acidification are recognized global threats to reefs and require large- scale solutions, whereas the newly recognized threats to coral reefs caused by dead zones are more localized,” Altieri said.
He said his findings can be extrapolated to coral reefs worldwide, adding that such dead zones may be common in the tropics but have gone largely unreported, simply because scientists never looked for them.
“Based on our analyses, we think dead zones may be underreported,” said Nancy Knowlton of the Smithsonian’s National Museum of Natural History and study co- author.
“For every one dead zone in the tropics, there are probably 10 — nine of which have yet to be identified,” she said.
A dead zone occurs at the bottom of a body of water when there isn’t enough oxygen to support marine life. Also known as hypoxia, it’s created by nutrient runoff, mostly from overapplication of fertilizer on farms.
The Gulf of Mexico has an annual dead zone that typically forms in the summer, which varies in size from year to year. The Chesapeake Bay also has an annual dead zone.
Nutrients such as nitrogen can spur the growth of algae. When the algae die, their decay consumes oxygen faster than it can be brought from the surface, the National Oceanic and Atmospheric Administration said. Fish, shrimp and crabs can suffocate.
Sponges die from lack of oxygen in the water.