x Abu Dhabi, UAEThursday 27 July 2017

The deep impact on the Gulf's coral reefs

The Arabian Gulf's coral reefs have been devastated by rising temperatures and coastal developments, but Mother Nature is fighting back, providing a healthier habitat for marine life.

Brain coral, known as Faviid Playgyra has been discovered on the lee side of a breakwater near Marina Mall in Abu Dhabi. Antonie Robertson / The National
Brain coral, known as Faviid Playgyra has been discovered on the lee side of a breakwater near Marina Mall in Abu Dhabi. Antonie Robertson / The National

When teachers Steve and Anna Elwood moved from downtown Abu Dhabi to Raha Beach last May, they brought out their snorkelling equipment to see if any sea life had colonised the new shoreline.

Given that building work at Al Zeina had barely finished and the rock breakwater had only been in place for less than a year, their expectations were low.

“We do a lot of snorkelling around Dibba so we went out to see what was there,” Anna recalls.

“Given how much construction work is happening on the Abu Dhabi coast, we weren’t expecting much. We thought we’d only see a couple of tiny fish.

“We were really impressed about how many big fish we saw. We saw much more than we expected to see. We were seeing schools of 15 to 20 fish.”

It was more than just fish. Boulders that had until recently been part of the Hajar Mountains were now supporting colonies of colourful sponges alongside sea squirts, starfish and oysters. Above the waterline, egrets and cormorants are now a familiar sight along the new beach. The complex’s lifeguards have also reported regularly seeing pods of dolphins cruising the channel separating Raha Beach from Yas Island.

“It just shows you how nature recovers,” she adds.

That same story has been playing out at the other end of the capital for 20 years, where the coral colonies that have been growing on the Lulu Island breakwater are now reaching maturity.

John Burt, a marine biologist at New York University Abu Dhabi, says that while coral in the Gulf is generally in decline, such offshore breakwaters have helped create “dense and diverse” marine ecosystems, even if that was never the intention behind their creation.

“They represent an ecological improvement because they’re a hard substrate and they’re also complex, and therefore an improvement for fish,” he says.

“They’re colonised within a couple of months by fish. Coral is very slow [to grow], but Lulu Island is approaching what we call a mature community. There are points on Lulu Island that are fairly heavily encrusted with coral.”

However, he says those examples of nature adapting to the changed environment are at odds with what is otherwise an unrelenting succession of bad news for the marine ecosystem of the southern Gulf.

One reason for Burt’s presence in the UAE is because the Arabian Gulf serves as a natural laboratory to study coral reef ecology in extreme environments.

The Gulf is rated as the world’s warmest sea and the site of increasingly frequent mass bleaching events, where sustained warmer temperatures cause the coral to expel the algae that provide 90 per cent of the coral’s food source. If sustained, heat stress will kill the host coral.

No such events were recorded in the Gulf from 1950 until 1981 but since that first incident, there were two more in the 1990s and three since 2000, including the last two summers.

Burt says the way species cope here will predict how reefs elsewhere will adjust to rising sea temperatures caused by climate change.

But if the Gulf’s natural coral reefs are the equivalent of a canary in a coal mine, this is not a canary that is likely to be accepted for life
insurance. “These reefs are described as the most damaged in the world,” he explains.

“We’ve effectively lost 70 per cent of our reefs. Another 20 per cent is at risk. Only three per cent are considered to be relatively pristine. These impacts have already happened.”

Compare that with the worldwide figure in which one fifth of reefs have been destroyed by factors such as bleaching or development.

Burt is able to rattle off many more depressing statistics: fish stocks in this part of the Gulf have dropped by 81 per cent since 1978, some of the best coral reefs in the area were destroyed by construction of the Palm Jebel Ali, and reefs in the vicinity that survived the development are in serious decline.

But Dubai’s offshore mega-projects also demonstrate that coastal development has produced mixed fortunes for the areas’ marine ecosystems, even if the benefits were often not intended.

Dubai’s best-known examples, the Palm Jumeirah and The World, did not come at the cost of natural coral reefs because the seabed there was sand, but they have the effect of serving as artificial reefs.

“In Dubai, breakwaters are more important than natural reefs,” Burt adds.

“They’ve become large-scale artificial reefs. If you look at the breakwaters in the Palm Jebel Ali and the Palm Jumeirah, we have a density of fish, including commercially important species.

“Dubai’s natural reefs were 10 square kilometres in area. [The breakwaters] are an area of 350 square kilometres.

“Yes, we’ve impacted natural reefs, but we’ve created these large-scale artificial reefs that are many orders of magnitude larger in size.”

The ecosystem is different, with the result that the species that occur on breakwaters are not the same as those that occur on natural reefs.

Because the breakwaters are above the sea bed, they suit coral species less tolerant of sedimentation, but fragile species tend to be under-represented because breaking waves make it a high-energy environment.

“There are differences in these communities. They’re not the same as you get on a natural reef.

“You get some species that are less common on breakwaters, such as species that use the interstitial spaces, like damsel fish, which are reliant on coral. You get fewer species of coral, such as the relatively fragile ones. Natural reefs are low-energy environments because they’re deeper in the water.”

Of the 43 types of coral identified in the southern Gulf, only three are found on breakwaters.

The breakwaters off Dubai and Abu Dhabi are not the only unintended benefits that flow from offshore developments. The effective result of these offshore islands is that no commercial fishing occurs there.

“A lot of these coastal developments have become de facto marine protection areas,” Burt says.

“That includes these residential developments, but it also includes the oil rigs in the Gulf.”

Tight security means no fishing vessels can get anywhere near the oil rigs, with the result that each one becomes, in effect, a marine reserve.

That difficulty of access extends to marine biologists seeking to quantify if they act as fish havens.

“The evidence I’ve seen suggests that they are. They provide large 3D structures in areas typically dominated by sand,” Burt says.

The same dynamic works in places such as Al Zeina, where the marine environment is mostly sand and mud, so the introduction of hard surfaces such as the boulder breakwaters and concrete walls will increase the number of species present.

“It will have a positive impact on local biodiversity at that site,” he says. “In Al Zeina, the marine life will get more complex. Diversity will ramp up.”

That is good news for the Elwoods. As Al Zeina fills up with families, others have discovered the snorkelling potential on their doorstep.

“There’s a massive crab there – about a foot and a half across – and it was always around the same place about two to three metres down, just chilling out,” Anna says.

“It’s nice, having our own mini snorkelling area. I’ve had a look at some of the other breakwaters in Raha Beach and there have been beautiful parrot fish that were up to two hand-spans in size.

“It’s been a very pleasant find for a couple of outdoorsy people. When we can’t get away to Dibba, we come down here after work.”