Wanted: Rare coral sightings

The Department of Environment is on the hunt for staghorn and elkhorn coral in the Cayman Islands and is appealing to the swimming, snorkelling and diving public to help keep track of these rare branching corals.

This critically endangered coral was once common in Cayman but is now a rarer sight, having been reduced by up to 95 per cent over the past 30 years due to coral bleaching, disease, hurricanes, sedimentation, nutrient enrichment and habitat damage.

Once they receive feedback from the public on where staghorn and elkhorn corals have been spotted, Department of Environment staff will visit the reported locations of the coral and map the distribution of the elkhorn and staghorn, as well as assess their condition and identify potential threats.

“Staghorn and elkhorn corals are a relatively fast-growing branching corals, which means they provide a considerable amount of complex reef structure that forms important habitat for reef creatures,” said Tim Austin, deputy director of the Department of Environment.

“These two species of corals were once the most dominant and important shallow water reef-building species in the Caribbean, but a precipitous decline beginning in the early 1980s, due primarily to diseases, has reduced their abundance by up to 95 per cent. Today, only small remnant populations survive, and it is these areas that we are trying to identify and map in our recent research efforts,” he added.

Staghorn and elkhorn corals are listed as critically endangered on the International Union for Conservation of Nature’s Red List of Threatened Species. “Their listing reflects the fact that there has been a population reduction exceeding 80 per cent over the past 30 years due, in particular to the effects of disease, as well as other climate change and human-related factors,” said Mr. Austin.

In 2006, the United States, through the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service, also listed the two coral species on their Endangered Species Act, giving them special status for protection and restoration work.

The Acropora genus, in which these two corals are found, forms the most abundant and species-rich group of corals in the world. Only three of the species of this genus are found in the Caribbean and around the Cayman Islands – staghorn coral (Acropora cervicornis), elkhorn coral (Acropora palmata), and fused staghorn (Acropora prolifera), which is a hybrid of the two.

Workshop scheduled

The National Oceanic and Atmospheric Administration is funding an Acropora Workshop in the Cayman Islands on 16, 17 and 18 April. The workshop, organised by the Coral Reef Research Club at St. Matthew’s University’s School of Veterinary Medicine and the Coral Disease and Health Consortium.

The goal of the workshop is to provide a method to assist coral reef managers, particularly those with limited resources, to assess and manage the health of their respective coral populations.

Scott Taylor from SMU, who is coordinating the workshop, said the purpose of the three-day event is to get “different professionals together and sit down and work out ways we can deal with some of the problems we are seeing with Acropora”.

“There will be people who regularly go out and do surveys on the reef and count corals and measure corals… There will be people who study coral diseases and how diseases are spread around the reef throughout the region. There will also be animal health professionals, and that is where the veterinary school comes in. We have people who regularly work with animal diseases and we are looking at the same types of microbes seen in coral as we do in other animals,” he said.

A combination of natural and human-induced stressors have affected the staghorn and elkhorn corals, locally and regionally, over the years.

“Staghorn and elkhorn corals require very clear waters with high sunlight, lots of water movement (waves and currents) and good water quality in which to thrive. Land-based sources of pollution, such as runoff, sewage discharge, dredging and coastal development have all increased nutrient levels, sediment loading and turbidity contributing to poor water quality,” said Mr. Austin.

He added that runoff can also reduce oxygen levels and possibly introduce disease pathogens and that high nutrient levels can also allow large fleshy algae, known as macroalgae, to overgrow corals.

Diseases

“The two most significant diseases affecting staghorn and elkhorn corals are white-band disease and white pox/patchy necrosis. These two diseases are thought responsible for the rapid decline of these corals throughout the 1980s,” Mr. Austin explained.

Corals have also been affected by climate change and its associated increased water temperature and elevated light levels that are believed to cause bleaching, reduced coral growth rates and deposition rate of their calcium carbonate skeleton.

“Overfishing and disease have caused a reduction in a number of important predatory fishes such as groupers, and herbivores (plant eaters) such as parrotfish. Reduction in numbers of predatory fishes can also lead to an increase in organisms that feed on staghorn and elkhorn, such as the short coral snail, fireworm, and damselfish.

“Furthermore, without a healthy herbivorous fish population, macroalgae growth limits the recovery of stressed corals and the settlement of new baby corals to replace those that have been lost from disease, bleaching, predation and overgrowth,” said Mr. Austin.

When you spot them…

Anyone who spots the elkhorn or staghorn corals is asked to email the Department of Environment on [email protected] and give details about which species was spotted (staghorn or elkhorn); location of the sighting, with a detailed description of the distance from shore and the depth of water; when the coral was sighted; how much area was covered by the coral; its condition, including details of whether it was diseased, bleached, healthy, etc.; and any other notes or comments.

Those who send information to the department are also asked to include their contact information so they can be reached if further details are needed.

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Staghorn is critically endangered.
PHOTO: Chris and Joanna Humphries
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