If you were swim or diving off the sea-coast of Votua , Fiji a few twelvemonth ago , you might have date something strange : Two guys screwing plastic bottles into the sand and putting hunk of precious coral on a automobile balanced above the water on a pole . This was n’t performance graphics , but scientists illustrating that the previous byword “ the enemies of my enemies are my acquaintance ” holds true even on a coral Rand .
Coral Reef are in trouble . They ’re degrade world - wide , and the tropic Pacific has lost around half of its coral in just the last few decades . On these Pacific Witwatersrand , one of the major causes of coral red is predation by the crownwork - of - thorns ocean star ( Acanthaster planci ) , which eat out at coral and opens the door for seaweeds and other algae to get along in and contend for resources with whatever coral is left standing . That ’s bad not only for the corals , but other plants and animate being that look on the reefs for home ground and solid food . A sea star outbreak , say biologistMark Hay , can be withering and have cascade down event on many other species .
However , Hay has recentlyfoundthat seaweed is n’t always trouble for precious coral . In fact , in the right circumstances , the coral ’ challenger can become their accomplices against the sea stars , turning from “ pure foe into body guards . ”
Hay and marine biologist Cody Clements study coral , sea stars , and algae in a few spots around Votua on Fiji ’s “ Coral Coast ” to see how their interactions affect coral growth and survival of the fittest . This is where the nursing bottle number in . They collected coral branches from 20 different colonies and glued them to the reduce - off necks of charge plate soda bottles . The bottle cap were embed in the seabed and the cervix were screwed back in . These experimental corals were then surrounded with dissimilar amounts of chocolate-brown seaweed fronds . The researchers returned to the corals monthly to weigh them , using a waterproofed electronic plate that they view as above the water on a tripod .
The pair found that coral growth decreased as seaweed density increased , which was n’t surprising — but they also discovered that more seaweed top foreshorten the corals ’ chances of being lash out by sea stars . Once the seaweed covered about 40 to 60 pct of the coral ’s control surface , its chance of being attacked leave out to zero . Even seaweed - address corals that were snipe suffered less scathe than red coral that had none on them .
A seaweed cloak , Hay and Clements say , appears to keep the ocean virtuoso from detecting , getting to and feast on the precious coral . Sargassum polycystum , which is the type of seaweed the scientist worked with , as well as many other seaweed in the region , are tough and abrasive , and form thick canopy around coral Colony . That has costs for the precious coral , but also provide a ocean superstar - test copy covering that can give them a chance to pull through attacks and recover . The corals ' competitors wind up up supply a nett benefit .
Fiji ’s precious coral have another ally . During their research Hay and Clements met a local humankind who collect crown - of - thorns ocean stars from the reefs and apply them as fuel for bonfires on the beach , an fast-growing strategy that they say might aid corals elsewhere .
