Smith­so­nian flags ‘ dead zones’ that threaten co­ral reefs

Low- oxy­gen ar­eas choke off marine life

Chicago Sun-Times - - NATION/WORLD - Doyle Rice @ us­ato­day­weather USA TO­DAY

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.

SMITH­SO­NIAN TROP­I­CAL RE­SEARCH IN­STI­TUTE

Sponges die from lack of oxy­gen in the wa­ter.

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