Increased activity of El Nino was the cause of the extinction of coral reefs in the Pacific ocean approximately 4 - 1,5 thousand years ago - the scenario can be repeated in the near future due to climate change, reinforcing this climatic phenomenon, oceanographers say in the article, published in the journal Science.

This "Bush" coral dies due to warming waters in the Pacific ocean, which carries with El Nino
© Photo: Lauren Toth

The phenomenon of El Nino (oy" in Spanish) is characterized by an abnormal increase in the temperature of surface water in the Central and Eastern tropical zone of the Pacific ocean. This process is the reverse of the La Nina ("girl"), that is, on the contrary, with a cold snap in the same zone of the ocean. These conditions follow each other with intervals of about a year.

And El Nino and La Nina effect on the scheme of circulation of ocean and atmospheric currents, which in turn affects weather and climate around the globe, causing droughts in some regions, and heavy rains in others.

Climate chronicle of the ocean

A group of biologists and climatologists under the leadership of Richard Aaronson (Richard Aronson) from the Technological Institute of Florida in Melbourne (USA) restored the history of the development of coral reefs in the Pacific ocean for the last six thousand years, studying the remains of coral reefs in the coastal waters near the Islands of Contador and Iguana, to the West of the Panama canal.

As the scientists explain, coral colony is one of the most sensitive indicators of climate change in the waters of the ocean. The slightest change in the average water temperature, movement of currents and acidity impact on the ability of corals to build calcareous shells. In particular, the warming of the water and increase the acidity prevent polyps to capture ions of calcium and carbon dioxide, which negatively affects the health of coral reefs.

Aaronson and his colleagues extracted deposits of fossilized shells, corals for the last six thousand years, and have calculated the rate of their growth. It turned out that about four thousand years ago the formation of new polyps actually stopped. Scientists do not believe so unexpected results and checked them, having studied sediments coral reefs off the coast of Japan and Australia. The new data confirm the initial findings oceanographers.

Boy" and corals

"We were shocked by the fact that in the sediment was simply no traces of growth for 2,5 thousand years of history. This time lag is approximately 40% of the total duration of the studied period. Coral reefs are considered to be sufficiently resilient ecosystems, and so powerful, large-scale and prolonged collapse, most likely, was caused by the climate changes. This change was the strengthening El Nino" - said one of the participants of the group Lauren He (Lauren Toth) from the Technological Institute of Florida.

As the scientists explain that the collapse of coral reefs in the Pacific coincides with the strengthening El Nino at this time due to periodic climatic fluctuations. Increasing strength El Nino resulted in the increase of water temperature and other changes adversely affecting the life of the colonies of polyps.

According to oceanographers, further changes in work flows and growth in average temperatures in the Pacific ocean due to climate change may lead to similar consequences.

"Climate change could once again to destroy coral reef ecosystems, but in this case, the main reason is ' attack" of humanity on the environment and the effect of the death of corals will be longer. Local problems such as water pollution and overfishing, must be stopped, but their strength is fading before climate change, which is the main threat to reefs today", says He.