Extraordinary discovery of a coral reef off the coast of Iraq

Several colourful brittle stars wrap around octocoral.
Several colourful Ophiotheia venusta brittle stars wrap around octocoral Menella sp in the newly discovered reef.

ResearchBlogging.org A remarkable coral reef appears to be thriving in the murky waters of the northern Persian Gulf, despite seemingly harsh environmental conditions. 

A living coral reef has been identified in the coastal waters of Iraq for the first time ever. Surprised that a reef could exist undetected for so long, scientists carried out numerous diving expeditions to reveal that this is not a typical coral reef.

The coastline of Iraq is small, extending for a mere 58 km along the north of the Persian Gulf. The waters are dominated by outflow from the great Shatt-al Arab river, into which both the Tigris and the Euphrates flow. These rivers carry a huge amount of sediment with them, much of which is dumped straight into the Gulf, clouding the seawater and reducing the visibility to less than 1 m. In addition, the water is often fouled by oil pollution and temperatures can rapidly plunge from 34 to 14°C.

These conditions would normally be inhospitable for most coral species. And indeed the nearest reefs previously known are the fringing reefs off southern Kuwait. These are found in warm shallow clear waters and are extremely sensitive to any changes in environmental conditions. But the 28 km2 reef off Iraq, named the Palinurus Rock Reef, appears to be dominated by far hardier species which are able to tolerate the cool and muddy waters.

The diving team identified a number of both stony (Scleractinia) and soft (Octocorallia) corals, several of which were confirmed to be slow-growing massive species that can withstand strong currents. Wonderfully, several ophiuroids (brittle stars, serpent stars and basket stars) were also discovered – still very little is known about the ecology of these animals in the Persian Gulf. But the researchers were most surprised to find several sponges (Porifera) in the reef, which usually would be unable to survive in waters with such a high sediment load.

The discovery of this Iraqi reef serves to highlight just how little we still know about coral reefs and the species that live on them. It certainly appears than some species are far more robust than previously believed and are able to adapt to even the most stressful of environments. With reefs throughout the world currently under threat from climate change, acidification, pollution, and blast fishing, the persistence of this reef gives hope that others will be able to adapt to future changing conditions.

Reference: Pohl T, Al-Muqdadi SW, Ali MH, Fawzi NA, Ehrlich H, & Merkel B (2014). Discovery of a living coral reef in the coastal waters of Iraq. Scientific Reports, 4 PMID: 24603901

Image: Thomas Pohl

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