Coral plant­ing of­fers hope for reefs

Sci­en­tists have learned to re­grow coral – and re­vive dam­aged ar­eas

The Guardian Weekly - - International News - Oliver Mil­man

As an ocean early warn­ing sys­tem, coral reefs have been sound­ing the alarm for years. They have been bleached white by marine heat­waves and killed off en masse by a com­bi­na­tion of fac­tors in­clud­ing pol­lu­tion, over­fish­ing, acid­i­fi­ca­tion and cli­mate change.

But now sci­en­tists in Florida, and other trop­i­cal lo­ca­tions, are at­tempt­ing to stop the rot by creat­ing coral “nurs­eries” in which young pop­u­la­tions can be raised in con­trolled con­di­tions be­fore be­ing planted on de­nuded reefs. Off the south­ern tip of Florida, a sprawl­ing marine farm­ing oper­a­tion has been es­tab­lished in which corals are painstak­ingly grown on an­chored fi­bre­glass trees and then planted on the bar­rier reef.

“The idea is to do as much as we can now to give these coral pop­u­la­tions a fight­ing chance,” says Jes­sica Levy, pro­gramme man­ager at the Coral Restoration Foun­da­tion. “If you don’t put back the ma­te­rial and di­ver­sity that has been lost, the pop­u­la­tions are go­ing to crash and be­come ex­tinct. For reefs, you’re look­ing at a global ex­tinc­tion of the ecosys­tem if things don’t change quickly.”

Florida has the world’s third-largest bar­rier reef, with nearly 1,400 species of plants and an­i­mals and 500 species of fish, but the reef is van­ish­ing fast. Re­search found roughly half has dis­ap­peared over the past 250 years. Cov­er­age of acro­p­ora, the pri­mary genus of reef-build­ing corals, has plum­meted 97%. “The reef is pretty bar­ren right now,” says Levy.

The mal­adies are nu­mer­ous and stretch back decades. A bur­geon­ing Florid­ian pop­u­la­tion and mass tourism have led to wa­ter pol­lu­tion and di­rect dam­age to corals, while agriculture has sent tor­rents of nu­tri­ents flow­ing on to the reef.

Although reg­u­la­tions have curbed some of these lo­cal risks, cli­mate change re­mains a big threat. In 2014 a spike in wa­ter tem­per­a­tures led the Florida corals to bleach – when a reef ex­pels its sym­bi­otic al­gae un­der heat stress, whitens and po­ten­tially dies.

It hap­pened again in 2015, as a pro­longed global bleach­ing event gripped the planet’s corals. Aus­tralia’s Great Bar­rier Reef was cooked to the point that it re­port­edly smelled of death.

The world is on course for a tem­per­a­ture in­crease that will com­fort­ably wipe out most of the coral ecosys­tems, a sce­nario that would strip away a cru­cial nurs­ery and smor­gas­bord for count­less marine species, di­min­ish fish­eries and re­move a vi­tal buf­fer to storms that will in­ten­sify as the planet warms.

“The out­look for the Florida reef is grim,” says Kim Cobb, a coral ex­pert at Ge­or­gia In­sti­tute of Tech­nol­ogy. “The threats are over­whelm­ing. Just as the reef is climb­ing out of decades of sys­temic prob­lems it is un­der in­creas­ing threat from cli­mate change.”

The Coral Restoration Foun­da­tion has in­creased coral re­plant­ing as the sit­u­a­tion has de­te­ri­o­rated, and the foun­da­tion’s un­der­wa­ter trees are be­com­ing sought-after items for stressed reefs around the world. Part­ner­ships have formed to pro­vide trees to places such as Ja­maica and Colom­bia. A char­tered fish­ing oper­a­tion in Mex­ico is in talks to do the same. Last month, it was an­nounced 100 corals had been suc­cess­fully planted on the Great Bar­rier Reef, the world’s largest liv­ing struc­ture, us­ing the tree frames.

The oper­a­tion came about after trop­i­cal fish col­lec­tor Ken Ned­imyer no­ticed a rare type of coral called Acro­p­ora cer­vi­cro­nis grow­ing on his “live rock” farm in 2003. A loop­hole in en­dan­gered species laws meant the coral was his to keep, so he be­gan cut­ting it up to grow new coral from frag­ments. Ned­imyer hoped to re­grow enough coral to start patch­ing up Florida’s reef. Ini­tially, the frag­ments were mounted on sunken con­cen­tric blocks that mim­icked reefs. But the real break­through came in 2011 with the de­vel­op­ment of fab­ri­cated trees on which dozens of pieces of coral can be dan­gled from the branches.

Backed by fund­ing from the fed­eral govern­ment and con­cerned donors, the foun­da­tion now has about 700 trees ar­ranged in seven nurs­eries along the reef sys­tem as far as Key West. Re­trieved frag­ments of wild coral are sliced into finger-sized pieces, sorted into ge­nomic types and strung from the fi­bre­glass and PVC trees, which are an­chored to the seabed and buoyed with a float. Along­side the staghorn and elkhorn corals, sway­ing gen­tly on lines in the cur­rents, are boul­der-cov­er­ing corals that are mounted on nearby plat­forms.

This en­vi­ron­ment lets the corals grow three times faster than nor­mal. Even so, it takes up to nine months for them to reach the size of a small foot­ball, at which point they are taken to be at­tached to an ap­pro­pri­ate reef us­ing a spe­cial putty. So far in 2018 more than 18,000 corals have been planted on to reefs, dou­ble that achieved an­nu­ally five years ago. Around eight in 10 planted corals sur­vive at least a year.

This work is la­bo­ri­ous and oc­ca­sion­ally fraught. The trees need to be reg­u­larly cleaned of de­tri­tus, while about 300 coral geno­types across nine species must be sorted and tagged. Re­grown coral can be swiftly wiped out by hot or cold snaps, storms or disease. Hur­ri­cane Irma stripped corals off the trees, although the struc­tures them­selves were al­most all un­scathed. “We lost a fair bit of stock with Irma,” says Levy. “This work can be very hard as well as very re­ward­ing. You plant corals and watch them grow for sev­eral years and then some­thing out of your con­trol can hap­pen.”

The largest of the nurs­eries, lo­cated 5km off the Key Largo coast, has about 500 trees, which look a bit like giant, an­ti­quated TV ae­ri­als. Branch­ing staghorn and elkhorn coral dan­gle from the trees just three me­tres un­der­wa­ter.

A con­stel­la­tion of marine life, such as trum­pet fish, hog fish and trig­ger fish, flit be­tween the trees. A nearby reef site is dot­ted with re­planted corals bear­ing the tags of the Coral Restoration Foun­da­tion, although the over­all coral cov­er­age is scant.

The bleak scene is com­pleted by stands of life­less pil­lar coral, rav­aged by a bac­te­rial disease that swept through the Keys last sum­mer. A nearby brain coral is split by jagged white lines, fur­ther ev­i­dence of disease. The ori­gins of many coral dis­eases are vague but at least one ma­jor out­break has been linked to hu­man fae­cal waste: the Keys only gained a fully func­tion­ing sewer sys­tem dur­ing the past decade. Re­cent re­search has found that these dis­eases will worsen as the oceans warm.

The scale of the foun­da­tion’s task is “mon­u­men­tal”, says Cobb. But the restoration work could help pro­vide a life­line for reefs, she says.

A trum­pet fish swims through a coral nurs­ery off the Key Largo coast­line

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