The world's coral reefs face increased disruption to their ability to breed and recover from damage, as global warming whips up more powerful and frequent hurricanes and storms, says study.
"We have found clear evidence that coral recruitment, the regrowth of young corals, drops sharply in the wake of a major bleaching event or a hurricane," said lead study author Dr. Jennie Mallela of the ARC Center of Excellence for Coral Reef Studies and Australian National University.
AdvertisementUsing the island of Tobago in the Caribbean as their laboratory, Dr Mallela and colleague Professor James Crabbe of the University of Bedfordshire, UK, backtracked to 1980 to see what had happened to the corals in the wake of nine hurricanes, tropical storms and bleaching events.
"In every case, there was a sharp drop in coral recruitment following the event, often by as much as two thirds to three quarters. Not only were fewer new coral colonies formed, but also far fewer of the major reef building coral species recruited successfully," Jennie said.
"This finding mirrors our modeling studies on the fringing reefs of Jamaica, and on the Meso-American Barrier reef off the coast of Belize," said Professor Crabbe.
Tobago lies outside the main Caribbean hurricane belt and therefore is more typical of the circumstances of most coral reefs around the world.
Nevertheless, its corals are disrupted by a major storm or bleaching every three or four years, and the frequency of this may be growing.
"Climate researchers are seeing increasing evidence for a direct relationship between global warming and rising hurricane intensity as well as frequency," Jennie explained.
"Global warming produces significant increases in the frequency of high sea surface temperatures (SSTs), and hurricane winds are strengthened by warm surface waters," she said.
The high temperatures cause bleaching, while the storms inflict physical destruction on the corals as well as eroding the rocky platforms they need to grow on, or burying them in sand.
"Maintaining coral reef populations in the face of large-scale degradation depends critically on recruitment, the ability of the corals to breed successfully and settle on the reef to form new colonies. Our research suggests this process is severely disrupted after one of these major events," said Jennie.
According to Jennie, the concern is that if major storms and bleaching become more frequent as the climate warms, the ability of individual reefs to renew themselves may break down completely.