Coral gets bailed out by an en­emy: study

The China Post - - LIFE GUIDE POST -

Un­der at­tack from hordes of ravenous starfish, Pa­cific coral is get­ting help from an un­ex­pected source — sea­weed, an arch en­emy, re­searchers said on Wed­nes­day.

Sea­weed is no friend of the frag­ile ecosys­tems of coral reefs, pump­ing out harm­ful chem­i­cals, block­ing out life-giv­ing sun­light, and rub­bing up against and dam­ag­ing the threat­ened marine in­ver­te­brates.

But it turns out the plants also fend off coral-munch­ing crown-ofthorns starfish, which pose an even big­ger threat, ac­cord­ing to a study pub­lished in Pro­ceed­ings of the Royal So­ci­ety B: Bi­o­log­i­cal Sciences.

So be­ing cov­ered in sea­weed rep­re­sents the lesser of two evils for coral: “bet­ter than be­ing eaten,” said study co-au­thor Cody Cle­ments, a grad­u­ate stu­dent at the Ge­or­gia In­sti­tute of Tech­nol­ogy in the United States.

“Corals sur­rounded by sea­weeds were vir­tu­ally im­mune to at­tack by the sea stars, es­sen­tially con­vert­ing sea­weeds from en­e­mies to friends,” said co-au­thor Mark Hay, a pro­fes­sor at the univer­sity.

The re­search could be help­ful in man­ag­ing coral reefs, which are un­der in­creas­ing threat from cli­mate change, chem­i­cal run-off from farm­ing, and the crown-of-thorns starfish.

Sea stars have a unique feed­ing mech­a­nism by which a sack-like stom­ach emerges from their mouth to en­velop and ex­ter­nally di­gest the corals’ liv­ing tis­sue, killing them.

“All they leave be­hind are the coral skele­tons,” said Cle­ments.

Crown-of-thorns sea stars are a ma­jor prob­lem in the Pa­cific, which is home to the world’s big­gest coral reef ecosys­tem, the Great Bar­rier Reef.

Its coral has de­clined by more than 50 per­cent over the past 25 years with sea stars get­ting much of the blame, the re­searchers said in a state­ment.

In a two-year study in a pro­tected marine area off the coast of the Fiji is­lands, Cle­ments ex­am­ined what sea stars and sea­weed did to coral.

He used por­ta­ble coral sam­ples to test their re­ac­tion to dif­fer­ent sizes of sea­weed growth.

In the ab­sence of sea­weed, coral mass more than dou­bled in about four months. But coral which shared its habi­tat with mul­ti­ple sea­weed fronds grew a mere 40 per­cent over the same pe­riod.

Re­searchers then moved on to study­ing sea star at­tacks, and found they tar­geted ex­posed parts and not those pro­tected by plant growth.

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