World / Science & Health

Coral reefs at risk of dissolving as oceans get more acidic: study

Reuters, AP

Coral reefs could start to dissolve before 2100 as man-made climate change drives acidification of the oceans, scientists said Thursday.

Acidification will threaten sediments that are building blocks for reefs. Corals already face risks from ocean temperatures, pollution and overfishing.

“Coral reefs will transition to net dissolving before end of century,” the Australian-led team of scientists wrote in the U.S. journal Science. “Net dissolving” means reefs would lose more material than they gain from the growth of corals.

Carbon dioxide, the main man-made greenhouse gas, forms a weak acid in water and threatens to dissolve the reef sediments, made from broken down bits of corals and other carbonate organisms that accumulate over thousands of years, it said.

The sediments are 10 times more vulnerable to acidification than the tiny coral animals that also extract chemicals directly from the sea water to build stony skeletons that form reefs, the study said.

Coral animals will be able to keep growing and replenish reefs long after sandy sediments start to dissolve, said lead author Bradley Eyre of Southern Cross University.

“This probably reflects the corals’ ability to modify their environment and partially adapt to ocean acidification whereas the dissolution of sands is a geo-chemical process that cannot adapt,” he wrote in an email.

The report said it was “unknown if the whole reef will erode once the sediments become net dissolving” and whether reefs ‘will experience catastrophic destruction’ ” or merely a slow erosion.

Some reef sediments were already starting to dissolve, such as at Kaneohe Bay in Hawaii, where other pollutants were contributing.

Eyre said it was unclear if the dissolution of sediments could be a long-term threat to entire islands, from the Pacific to the Caribbean. Other studies say that deep cuts in greenhouse gas emissions can limit acidification.

Most studies show that acidification will be overwhelmingly bad for ocean life, also threatening creatures such as oysters, lobsters and crabs. Another study Thursday, however, found that it might help the growth of some plants.

“An increase of carbon dioxide in the ocean theoretically could stimulate higher growth of kelp and seaweeds,” Kasper Hancke, a biologist at the Norwegian Institute for Water Research, wrote in a statement.

Wednesday, the tiny island nation of the Seychelles announced a pioneering marine conservation plan as part of a debt swap deal with creditors.

In an agreement described as the first of its kind, the Indian Ocean nation is designating nearly a third of its waters as protected areas, aiming to ensure the longevity of its unique biodiversity.

The archipelago’s 115 islands have been isolated by continental land masses for millions of years. The Aldabra atoll, a UNESCO World Heritage Site, is home to the world’s largest population of giant tortoises, critically endangered sea cows and spawning grounds for a number of rare species. But over-fishing has hurt their numbers.

The government Wednesday signed a bill restricting nearly all human activity in the waters around Aldabra and overall setting aside more than 210,000 square kilometers (81,000 square miles) as protected areas. The areas around Aldabra will ban all extractive uses such as fishing and petroleum exploration; the rest will be restricted to sustainable practices. The plan will be completed by 2021.

The deal with the country’s creditors was brokered by U.S.-based The Nature Conservancy and involved a $1 million grant by the foundation of actor Leonardo DiCaprio.

At the height of its debt crisis in the late 2000s, the Seychelles was one of the world’s top debt-ridden countries. Its sovereign debt peaked at nearly $1 billion, according to the World Bank. Today the debt stands at less than half of that, according to the finance ministry.

The deal allows for a certain amount of money to be repaid into a trust fund to support conservation-related projects, organizers said.