Coral suffers ‘osteoporosis’ from rise in ocean acidity

CORAL reefs develop “osteoporosis” as a result of the ocean becoming more acidic due to carbon dioxide emissions, scientists have found.

As carbon dioxide builds up in concentration in the ocean, it becomes more acidic, and this is impeding the growth of coral, a study in Geophysical Research Letters has revealed.

Scientists from the Woods Hole Oceanographic Institution (WHOI) in Falmouth, Massachusetts, found significant reduction in the density of coral skeleton along much of the Great Barrier Reef, the world’s largest coral reef system, and also on two reefs in the South China Sea, which they attribute largely to the increasing acidity of the waters surrounding these reefs since 1950.

“This is the first unambiguous detection and attribution of ocean acidification’s impact on coral growth,” said lead author and WHOI scientist Weifu Guo.

“Our study presents strong evidence that 20th century ocean acidification, exacerbated by reef biogeochemical processes, had measurable effects on the growth of a keystone reef-building coral species across the Great Barrier Reef and in the South China Sea.

“These effects will likely accelerate as ocean acidification progresses over the next several decades,” he adds.

The ocean has experienced a 0.1 unit decline in ph since the pre-industrial era, and scientists are just now discovering what effect that has on marine life.

Ocean acidification has led to a 20 per cent decrease in the concentration of carbonate ions in seawater. Calcium carbonate is what corals use to create their skeletons, so this decline means that they are at risk.

Because of the reductions in these concentrations, the density of their

‘Corals really need the strength they get from their density, because that’s what keeps reefs from breaking’

skeletons reduces, whittling away at the coral’s strength, much like osteoporosis weakens bones in humans.

“The corals aren’t able to tell us what they’re feeling, but we can see it in their skeletons,” said Anne Cohen, a WHOI scientist and co-author of the study.

“The problem is that corals really need the strength they get from their density, because that’s what keeps reefs from breaking apart. The compounding effects of temperature, local stressors, and now ocean acidification will be devastating for many reefs.”