Ocean acidity threatens coral reefs

Scientists warn that we may see coral reefs disintegrating due to carbon dioxide levels by 2100 as the oceans become more acidic. Research leader Dr Jacob Silverman, from the Carnegie Institution in Washington D.C. said: “These ecosystems, which harbour the highest diversity of marine life in the oceans, may be severely reduced within less than 100 years.”

This stark warning comes following a study of the impact of various factors upon the metabolism of coral reefs in the northern Red Sea. The research showed that the ability of the coral to build new structures depended strongly on water acidity and to a lesser extent temperature.

Dr Silverman said: “A global map produced on the basis of these calculations shows that all coral reefs are expected to stop their growth and start to disintegrate when atmospheric CO2 (carbon dioxide) reaches 560 parts per million (double its pre-industrial level), expected by the end of the 21st century.”

Corals reefs are built by the corals themselves which secrete a hard skeleton of calcium carbonate by extracting dissolved ions from the seawater. As the sea absorbs carbon dioxide, hydrogen ions are dissolved, this results in an increase in the acidity of the water. When the acidity level reaches a certain point, the corals are unable to extract the necessary minerals from the water and cannot continue to build their hard skeletons.

Corals are not the only organisms in the sea that rely on building calcium carbonate shells or internal structures (calcifying species). Molluscs, such as abalone, limpets and conch; crustaceans such as lobsters and crabs; coralline algae; and echinoderms which include star fish and sea urchins may all be affected by ocean acidification.

While the full ecological consequences of ocean acidification are still uncertain, it appears likely that many calcifying species will be adversely affected. If atmospheric carbon dioxide levels can be reduced and the increase in emissions which has been occurring since the industrial revolution can be halted, ocean acidification may not have such disastrous consequences. Read more..