Plas­tic In The Ocean? This Batch Is For Sci­ence

Soundings - - Dispatches - By Elaine Lembo

Areef- mim­ick­ing project in the Mediter­ranean Sea is de­ploy­ing plas­tic into the ocean, not re­mov­ing it. The tem­po­rary reef in the Gulf of La Spezia, off Italy’s north­west coast, should help de­ter­mine whether aquatic or­gan­isms can with­stand ocean acid­i­fi­ca­tion.

The 12-month ex­per­i­ment is a col­lab­o­ra­tion among sev­eral uni­ver­si­ties and agen­cies, says Fed­er­ica Ragaz­zola, of the In­sti­tute of Marine Sciences at the Univer­sity of Portsmouth in the United King­dom. It will test the in­flu­ence of coralline al­gae on nearby life forms. The idea is to see whether or­gan­isms liv­ing in­side the al­gae might have a sur­vival ad­van­tage in an era of cli­mate change.

“We don’t aim to put more plas­tic in the ocean,” she says. “We de­ployed lit­tle plas­tic reefs be­cause we want to test the buf­fer ef­fect of coralline al­gae on its as­so­ci­ated fauna. The plas­tic reef will even­tu­ally be re­moved from the sea and placed in an aquar­ium for the ‘acid test.’ ”

As the world’s oceans warm and acid­ify, co­ral fail to ab­sorb the cal­cium car­bon­ate they need to main­tain skele­tons. The re­sult­ing “bleach­ing” is a dis­solv­ing, or die-off, of the reef and a drop in ecosys­tem di­ver­sity.

Sci­en­tists clas­sify co­ral as an an­i­mal, but coralline al­gae is a seaweed. “Both have a cal­cium car­bon­ate struc­ture, but it’s ac­tu­ally a dif­fer­ent type of cal­cium car­bon­ate,” Ragaz­zola says. “There are a lot of or­gan­isms in the sea that have cal­cium car­bon­ate struc­ture.”

Red coralline al­gae’s car­bon­ate struc­ture is vul­ner­a­ble to ocean acid­i­fi­ca­tion; its sway­ing fronds, within which thrive myr­iad or­gan­isms, may act as a buf­fer, Ragaz­zola says. “To test this hy­poth­e­sis, we had to cre­ate an ar­ti­fi­cial reef which would mimic the struc­ture as closely as pos­si­ble to the real al­gae, but of course, it had to be made by some ma­te­rial other than car­bon­ate,” she says.

After 12 months, her team will re­move the ar­ti­fi­cial reef and some of the real reef, and test them in an aquar­ium with high car­bon diox­ide lev­els. The process should show whether the or­gan­isms are bet­ter off in the real reef or in the shel­ter of the al­gae fronds.

To copy the fronds of coralline al­gae, Ragaz­zola used a biodegrad­able elas­tomer, which is an elas­tic sub­stance like rub­ber. “We wanted to re-cre­ate the same struc­tural char­ac­ter­is­tic of the al­gae, which need to be able to bend and move with the cur­rents,” she says.

The plas­tic reef quickly at­tracted biofilm — a thin, slimy layer of bac­te­ria. It is es­sen­tial in the re­cruit­ment of other species, Ragaz­zola says. “We are now in­ves­ti­gat­ing some biopoly­mers that can de­grade and that could be used as ar­ti­fi­cial reef with the aim to re­store the reef,” she says. “Ide­ally they will dis­ap­pear, leav­ing only the re­cruited species form­ing the reef. So no ex­tra plas­tic in the ocean. We have plenty al­ready.”

The project is in the Med be­cause coralline al­gae are im­por­tant “bio con­struc­tors” there, Ragaz­zola says. “There’s no other project work­ing on a mimic sce­nario,” she says. “Usu­ally the restora­tion projects are more fo­cused on co­ral reefs.”

The depth of the ar­ti­fi­cial reef is about 4½ feet, same as the nat­u­rally oc­cur­ring reef. And it can with­stand a hu­man pres­ence; Ragaz­zola says chil­dren from a lo­cal sum­mer camp are tal­ly­ing new for­ma­tions while snor­kel­ing, pro­vid­ing an im­por­tant mon­i­tor­ing ser­vice. “We think this is a good way to get peo­ple in­volved in the project and will also help us to pro­tect the reefs,” she says. “One of the reefs was re­moved by a guy who wanted to take it home.”

Small plas•ic s•ruc•ures mean• •o mimic na•ural coralline al­gae may help de•er­mine whe•her or­gan­isms liv­ing in­side •he al­gae can •ol­era•e ocean acid­i­fica•ionm

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