A domino effect in coral reefs?

USGS coral reefs
A diverse coral reef in the U.S. Virgin Islands. PHOTO BY CAROLINE ROGERS/USGS.

Staff Report

Researchers who tended multiple patches of coral species in an underwater lab found that  diverse colonies are much more resilient than those comprised of single species.

A study led by Georgia Institute of Technology scientists found that the “effective extinction” of many coral species is making the remaining reef systems more vulnerable.

In experiments around Fiji, the marine scientists created single-species colonies of coral. When they dived down to monitor the patches, they found some of plots entirely wiped out and covered in algae.

“Rows of corals had tissue that was brown – that was dead tissue. Other tissue had turned white and was in the process of dying,” Cody Clements said in a press release describing the findings, published Jan. 2019 in the journal Nature Ecology & Evolution. The findings reinforce the idea that diverse ecosystems are often healthier, more resilient to impacts and more sustainable.

Working by kayak, Clements set up 48 concrete underwater tables with 864 coral “planters” made of cut-off plastic soda bottles. Then he planted different coral communities, some with single species, others mixed in different proportions. After 16 months, it was clear that the plots with more coral species grew better, while the single-species plots basically died.

The experiment will help scientists quantify biodiversity’s contribution to coral survival as well as the effects of biodiversity’s disappearance. It can also help improve reef restoration efforts.

Coral reefs around the world have been hit hard by global warming, especially during a recent mass global bleaching event from 2014 to 2016. Since the early 1980s, live coral reef cover in the Caribbean has declined from 60 percent to 10 percent.

As of 2008, about 20 percent of the world’s coral reefs had already been lost. Scientists expect another 20 percent to die within the next 10 to 15 years. By 2050, at least half of all coral reefs will be dead. If global warming can be capped at 1.5 degrees Celsius, perhaps 10 percent of corals can survive through 2100, but on our current emissions path, corals will probably be wiped out.

That’s bad news for the oceans because reefs are the nurseries for marine life, including many species that help feed people in coastal communities in developing countries.

Published by Bob Berwyn

Environmental journalist covering climate change, forests, water, mountains and biodiversity.

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