Plastic In The Ocean? This Batch Is For Science
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.”
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