x Abu Dhabi, UAEMonday 24 July 2017

For ocean life, what lies beneath?

Scientists are studying whether man-made structures offer the same quality of marine habitat as natural coral reefs.

? Because of extensive coastal development, Dubai now has more than 65 kilometres of breakwaters, which equals 500 square kilometres of rocky habitat.
? Only three species of corals are known to live on breakwaters. For comparison, natural reefs in the Arabian Gulf are home to 43 coral species.
? Breakwaters have dense fish communities but these consist of fewer species.
? Because of extensive coastal development, Dubai now has more than 65 kilometres of breakwaters, which equals 500 square kilometres of rocky habitat. ? Only three species of corals are known to live on breakwaters. For comparison, natural reefs in the Arabian Gulf are home to 43 coral species. ? Breakwaters have dense fish communities but these consist of fewer species.

They sprang up during the UAE's building boom to protect luxury beachfront properties, marinas and ports. Now marine scientists are examining whether the country's stretches of breakwater - of which there are 65km in Dubai alone - can protect life in the ocean as well as on the shore.

While many agree that the breakwaters have gradually attracted thousands of fish and coral species, doubts remain over whether they can ever replicate the diversity of life found on natural reefs. Although coral reefs cover only 0.2 per cent of the ocean floor, they are home to around a quarter of all marine creatures. Dr Christophe Tourenq, the science and research manager at the Emirates Wildlife Society-World Wide Fund for Nature, said he is sceptical that breakwaters can support such diversity. "Of course you will see fish on the artificial structures," he said. "The question is, are the populations as viable as on a natural reef?

"You can have thousands of fish on breakwaters, but they can be of one or two species only. Some species have very specific requirements and I don't think artificial structures fulfil these requirements." Dr John Burt, an assistant professor of biology at New York University-Abu Dhabi, spent several years studying breakwaters in Dubai. He was part of a scientific team, headed by the United Nations University's International Network on Water, Environment and Health, that was hired by the property developer Nakheel to study the environmental impacts of its large coastal projects and the changes in the marine ecosystem they brought about. The collaboration has yielded important results allowing for comparisons between natural reefs and breakwaters.

"In terms of coral and fish communities, you get different assemblages in these two habitats," said Dr Burt. "Coral communities on breakwaters, while abundant, are generally much less diverse than those in natural habitats, with over three-quarters of all breakwater corals made up by just three species," he said. In the Arabian Gulf, scientists have recorded 43 coral species. Breakwaters almost exclusively feature corals from the family faviidae, also known as brain coral. Table corals, which branch out horizontally, are almost exclusively found on natural reefs, said Dr Burt.

However, the picture is more complicated than a simple dismissal of the engineered structures, some of which have become healthy marine communitiesin their own right, providing a hard substrate for coral to settle and attract fish. "Coral communities on mature breakwaters can be quite extensive, covering more than half of the available substrate compared with just over a third on some of the more extensive reefs in Dubai," said Dr Burt. "Similarly, fish communities are quite dense on breakwaters, with more than three times the abundance on breakwaters compared with natural reefs in the summer," he said. "These observations support the suggestions that these are important man-made ecosystems in coastal environments, and that they do represent large-scale artificial reefs.

"All coral reefs have to have a hard substrate to start [growing]. By putting in breakwaters, we are creating this kind of habitat that coral and other associated fauna require for their existence." Whether breakwaters are able to serve these purposes depends on how they are designed. Through his research, Dr Burt has found out that the type of material used to build the breakwaters makes a difference. Gabro, a rock commonly quarried here, has great potential to attract corals. Concrete, on the other hand, does not. "Man-made structures can form an important component of the marine ecosystem in coastal urban areas, but both natural reef and breakwater communities are unique in their own right," said Dr Burt.

"This suggests that coastal development should be done in as ecologically sensitive a way as possible to prevent impacts to natural reefs, and that we can and should improve the ecological design of breakwaters". Nakheel said the breakwater surrounding projects, including the Palm islands, has "substantially increased" the amount of habitat for flora and fauna in the Emirate. "Before its creation, nearly all of the UAE coastline and seabed was sandy terrain," a spokesperson said. "The rock breakwaters provide areas of protected habitat for juvenile fish, which serve as the basis of the marine food chain."

The developer admitted it could not provide a replacement for reefs that were harmed by coastal development, but could offset the negative effects. "There is no replacement for natural coral reefs," the spokesperson said. "[But] the creation of tens of kilometres of coastal rock breakwater has provided substantially more eco-habitat than originally existed. [It] can be considered as mitigation to any negative impact."

But environmentalists still urged that the priority should be to protect the natural reefs. "Money should be put in protecting the existing natural reefs through efficient management and the creation of marine protected areas," said Dr Tourenq. @Email:vtodorova@thenational.ae