Study Shows Some Coral Try­ing to Adapt to Cli­mate Change

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A new study led by the Univer­sity of Mi­ami (UM) Rosen­stiel School of Ma­rine and At­mo­spheric Sci­ence dis­cov­ered that moun­tain­ous star coral—found in Florida and the Caribbean—can adapt to high wa­ter tem­per­a­tures and acid­ity con­di­tions. This could say coral reefs may yet sur­vive some of the short-term im­pacts of global warm­ing on the oceans.

The re­searchers ex­posed two threat­ened Caribbean reef-build­ing coral species, staghorn coral and moun­tain­ous star coral, to com­bi­na­tions of nor­mal (26 de­grees Cel­sius) and el­e­vated tem­per­a­ture (32 de­grees Cel­sius) and in­creased car­bon diox­ide lev­els (ph 7.8/800 ppm) for nine weeks. Ge­netic and phys­i­o­log­i­cal data such as skele­tal growth was then col­lected on the corals to de­ter­mine if stress events are recorded in a coral's skele­tal his­tory.

The re­searchers found that the staghorn coral was more sen­si­tive to heat stress. It ex­pe­ri­enced 100 per­cent mor­tal­ity af­ter 25 days at the el­e­vated tem­per­a­ture of 1.5 de­grees Cel­sius above the his­tor­i­cal max­i­mum monthly mean tem­per­a­ture for the Florida Keys. South Florida wa­ters could be­gin to ex­pe­ri­ence hot spells of this in­ten­sity and du­ra­tion once ev­ery five years by 2035, which ac­cord­ing to the re­searchers sug­gests that the species could be­come in­creas­ingly rare within 20 years.

The moun­tain­ous star coral sur­vived 62 days at the el­e­vated tem­per­a­ture and quickly re­cov­ered when tem­per­a­ture was re­duced at the end of the ex­per­i­ment. Re­duced ph did not af­fect sur­vival but did sig­nif­i­cantly im­pact growth un­der nor­mal tem­per­a­tures.

"Based on these re­sults we pre­dict that moun­tain­ous star coral will very con­ser­va­tively be able to tol­er­ate any warm­ing the Florida Keys is likely to ex­pe­ri­ence now un­til 2060 and very pos­si­bly to the end of the cen­tury," said Chris Lang­don, lead re­searcher and au­thor on this study.

Coral reefs are es­pe­cially vul­ner­a­ble to cli­mate change be­cause they are eas­ily af­fected by warm wa­ter. When ocean tem­per­a­tures rise, the al­gae that give coral its bright col­ors leave their host, caus­ing it to look white, a con­di­tion known as 'coral bleach­ing'. The loss of al­gae, which pro­vide coral with much of its en­ergy, make corals vul­ner­a­ble to star­va­tion and dis­ease.

The moun­tain­ous star coral had spe­cial al­gae, called D sym­bionts, which the re­searchers be­lieve made it able to adapt to the ex­per­i­men­tal cli­mate change con­di­tions.

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