Acidic ocean poses global coral reef threat

Many of the world’s coral reefs could begin to erode within 30 years as a result of increasing ocean acidity, according to new research co-authored by two researchers from SOEST and others.

The authors found that the sands which provide material for building and maintaining coral reefs will begin to dissolve due to increasing ocean acidity.

Their paper, published in Science, shows the rate at which coral reef sediments dissolve is ten times more sensitive to ocean acidification than the rate at which corals grow. Corals are expected to grow more slowly due to ocean acidification and this new study shows dissolving sands could greatly exacerbate reef loss associated with this reduction in coral growth.

“This study clearly shows that dissolution of coral reef sands is an important process that is ongoing in various locations throughout the world,” said Eric DeCarlo, SOEST oceanography professor and co-author of the study. “However, this process, which in an important factor in determining whether coral reef platforms will continue to accumulate or begin to disappear, had largely been ignored prior to this work.”

The researchers placed 57 benthic chambers underwater at a coral reef monitoring site in Kaneohe Bay maintained by DeCarlo, and three other reef locations in the Pacific and Atlantic Oceans to measure the impact of future seawater acidity in dissolving the sands that make up coral reef systems. Patrick Drupp, co-author of the paper and UHM oceanography graduate student at the time of the work, participated in the field work in Kaneohe Bay.

The research team then developed a model extrapolating their results for 22 coral reefs across the ocean basins.

Once the ocean reaches a tipping point in acidity, the reef sediments begin to dissolve faster than they accumulate. The time it takes to reach this threshold will depend on the rate of seawater acidification on the reefs. One study suggests more rapid acidification of seawater on reefs – which could mean that reef sediments start to dissolve by 2020. A slower rate of open ocean acidification would still mean that reef sediments will be dissolving at 20 of the 22 reefs modelled, before the end of this century.

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