Caribbean reefs losing species

(CNS): While reefs all over the world are at risk, those in the Caribbean have been devastated, according to research by the European Commission Environmental Department. In particular local reefs are suffering from the decline in population of two key species — the staghorn and elkhorn corals, which were recently listed under the US Endangered Species Act.

The Caribbean, states the EC, has the largest number of corals that are listed as Critically Endangered or Endangered. According to the research, climate change and human impacts are placing one-third of reefs at serious risk of extinction. Another area at risk aside from the Caribbean is the Coral Triangle in the western Pacific. Humans can have negative impacts on coral reefs through a number of means, including increased coastal development, sedimentation due to poor land-use and watershed management, sewage discharge, pollution from agrochemicals, coral mining and over-fishing, the EC said in a release.

“Coral reefs harbour the highest concentration of marine biodiversity in the world, form the basis of ecosystems and food webs that sustain communities and provide coastal protection,” it said. “Climate change and human impacts are placing one-third of reefs at serious risk of extinction. These impacts reduce the resilience of corals to withstand global threats from a rise in sea surface temperatures and increased ocean acidification arising from climate change. Higher temperatures lead to heat stress, which causes the coral to expel the zooxanthellate algae that live in their tissues in a protective, symbiotic relationship.”

The EC said researchers say this increases the risk of mass coral bleaching and mortality from diseases, some of which can kill 500 year old colonies within months. Additionally, ocean acidification is reducing ocean carbonate ion concentrations, which in turn limits the ability of corals to build skeletons and reef structures. Categories and criteria from the International Union for Conservation of Nature (IUCN) Red List were used to identify corals that are ‘Vulnerable’, ‘Endangered’ or ‘Critically Endangered’.

“The results emphasise the widespread plight of coral reefs and the urgent need for conservation measures. The majority of the species were found to be vulnerable. Of 704 species studied that could be assigned conservation status, 32.8 per cent were in categories with an elevated risk of extinction,” said the EC.

Researchers also found the proportion of corals threatened with extinction has increased dramatically over the last 2 decades and corals are at greater risk of extinction than any group of land-based animals apart from amphibians. Forty percent of coral species only inhabit shallow-waters and are therefore more vulnerable to human impacts and 303 species are highly susceptible to bleaching.