Corals in peril

Threats to Cayman’s corals from an encroaching white plague disease and other menaces may affect not just the corals, but also the very existence of the Islands, scientists warn.

Coral reefs are vital to Cayman’s future because they protect against hurricanes and form the foundation upon which the Cayman Islands are built.

Andy Bruckner, a coral reef scientist who was recently involved in monitoring the effects of white plague on some of the islands’ oldest corals and in training local divers and environmentalists to assess the impact of the disease, explained that the decline of the world’s coral could have disastrous effects.

“The entire Cayman Islands were built by coral initially. If you drill through the rock that’s here, all that is limestone that has been laid down by the corals,” he says. “Those corals are continuously trying to grow up towards the level of the ocean. We know that sea levels are rising and so, by having healthy corals, they’ll continue to keep up with that and the Cayman Islands  will be here indefinitely.

“If we lose all our corals, and the sea level rises, ultimately the Cayman Islands will be flooded – not in our lifetime, but with the predictions of how fast sea levels are rising, we’re going to lose places that are very important.”

Coral reefs are also vital for Cayman’s fish population since much of the local marine life depends on the reefs for shelter, nursery areas and breeding grounds.

And as the coral reefs decline and diminish, there is less protection for the islands in the event of severe hurricanes.

“These corals provide a barrier to storms. Without those corals, the [reef] structure will start to break down over time, so they may all die. You still will have the massive boulders for 10-15 years, but over time, other things will get in there that will corrode away the skeleton, causing it to collapse, and once you lose that physical barrier, hurricanes will cause a lot more damage when they come through the island,” Bruckner says.

He recently spent two and a half weeks in Cayman, checking 10,000 corals at 48 sites on Grand Cayman, Cayman Brac and Little Cayman with a team of other researchers and trainees.

White plague, believed to be a result of stress the corals suffered during mass bleaching due to higher sea temperatures last year, has hit large boulder corals on all three islands. These corals are the main frame-builders of the reefs. The disease can spread at a rate of 1 to 2 centimetres a day, causing massive impact on corals that grow a mere centimetre or less a year.

Bruckner, who works with the Living Oceans Foundation, says this year’s hurricane season, forecast to be one of the most active on record, may be a blessing in disguise for the corals because the hurricanes bring colder water, lowering the sea temperature and perhaps halting the disease.

But white plague is far from the only threat to the corals. They face many other hazards, some in the form of other marine life, like snails and damsel fish, and some from humans.

“In addition to the various algae/seaweeds overgrowing the reef and the various diseases, such as white plague, there’s of course the very prosaic boat groundings and anchorings, as well as any other direct destruction, such as from digging/dredging channels.. If the dredge silt washes out on to live coral, [it can] smother it ,” says John Bothwell, senior research officer at the Cayman Islands Department of Environment.

“For climate change, the bleaching stress to corals is the big one, but another long-term stress is ocean acidification,” he adds. “Basically, it makes it harder for corals to build their skeletons, which adds to their stress. Also, after the corals die, it makes the reef erode faster.”

Bothwell says the corals face almost too many threats to list. “That’s why it’s so important that we control the ones we can, like boat groundings and anchorings, general pollution, siltation and direct dredging work, etc, and participate in the big ones, like reducing carbon emissions for climate change,” he says.

The Department of Environment plans, budgets permitting, to begin more education, training and monitoring programmes to help protect Cayman’s coral reefs, as well as a more organised system of reporting anomalies spotted by divers at dive sites.

Bruckner believes education is one of the most important elements when it comes to protecting the reefs, especially from human  carelessness and interference. He cites tourist divers and snorkellers as one of the threats to the corals but believes that getting cruise ship and airline passengers to watch educational videos or read material about the importance, and delicacy, of the reefs could convince them to stop standing on corals while snorkelling or damaging them while diving.

“The weakest link is probably with the cruise ships when you have people going snorkelling. A lot of them will still stand on corals, they break it and you don’t want to do that… I think education will go a long way by making sure they are more responsible snorkellers and divers.”

Bruckner says corals are also at risk from developments on land that are built next to the coast or canals, especially when mangroves are removed, as these prevent run-off of waste into the sea and onto the corals.

While individual divers may not be able to do anything on their own about the larger threats of rising ocean levels, climate change and warmer seawater temperatures due to El Nino, there are steps they can take to ease pressure on the reefs, Bruckner says, but he stresses that divers need to be properly trained beforehand.

These steps include programmes to remove harmful pests from reefs, including a snail that is destructive to endangered elkhorn coral, and a species of damsel fish whose eating habits can lead to a coral being overrun with algae and seaweed.

“It would be possible, with training, to get volunteers – recreational divers or dive operators – to monitor some of those colonies and when they see the snails to remove them and to try to get the population back under control,” Bruckner says.

He envisions programmes similar to the efforts of local divers to control the invasive lionfish population to remove other pests from the reefs.

“We can’t really afford to lose any more coral. Corals are in a crisis worldwide, not just in the Cayman Islands. The Caribbean has been hit particularly hard. We traditionally have had 50 to 80 per cent of living coral cover on reefs throughout the region and most reefs now have 5 per cent, 7 per cent.

“The Cayman Islands is lucky because you still have a lot of coral. We still saw sites with 15-20 per cent coral cover, which is lower than you had two decades ago but still more [than elsewhere in the Caribbean] and you still have a lot of the important frame-building corals,” Bruckner says.

He also described other “low-tech” ways individuals can help the corals, such as simply picking up pieces of broken coral from sand underwater and placing them back in a site where they can continue to grow.

“A lot of times when a hurricane comes through, it breaks up a lot of coral. If that breaks up and lands on the reef, it is probably going to survive as long as the rest of the conditions are OK, because the coral is a colony. It’s like a plant where you can taking a clipping.

“Because you have reefs that have spurs and sand channels, a lot of the broken up coral lands on the sand. That’s going to die. So a major hurricane like… Ivan came through here, one of the things that could have been done was to mobilise large teams of divers to go out and pick up all that coral that’s still alive that’s in the sand and get it onto the hard bottom, not putting it on top of other corals, putting it into little holes and wedging it in place. A lot of that will attach to the bottom and grow into a new colony so you can save what’s left,” he says.

Local environmentalists hope that the proposed National Conservation Law will offer additional protection to Cayman’s coral. While the current Marine Conservation Law gives blanket protection to corals, one has to prove that damage to reefs has been done intentionally, and it does not offer specific protection to individual species.

Bothwell says the new law contains a list of individual species of animals and plants, including corals. “If there are particular species of coral in that area that are critical, they could get treated differently in an environmental impact assessment,” he says. “This will be a very long term thing we’ll have to work towards, but it’s laying the groundwork for… looking at a finer scale of potential problems,” he says.