Gerardia coral. Credit: OAR/National Undersea Research Program (NURP) Deep-sea corals are found on hard substrates on seamounts and continental margins worldwide at depths of 300 to around 3000 m. Deep-sea coral communities are hotspots of living things, both in terms of numbers and diversity of species. They provide critical habitat for fish and invertebrates.

According to research published this week in the Proceedings of the National Academy of Sciences, newly applied radiocarbon dating of the deep water corals Gerardia and Leiopathes species show that their growth rates are extremely low, and that individual colonies live for thousands of years. The longest-lived specimens were Leiopathes species (black corals) at 4265 years old.

The coral specimens were collected with submersibles off the coast of Hawaii. The authors measured the age of the corals’ proteinaceous skeleton and found that the corals grew much more slowly than previous dating techniques had shown.

The management and conservation of deep-sea coral communities is challenged by their commercial harvest for the jewellery trade and damage caused by deep-water fishing practices.

The scientists conclude that in light of the corals’ unusual longevity, we need to better understand their ecology and relationship with other bottom-dwelling creatures before forming a coherent international conservation strategy for these important deep-sea habitat-forming species.

Black Corals
Leiopathes black corals have a dark skeleton, after which they are named. The black skeleton forms irregularly branching, tree-like structures. Gorgonian-like, the skeleton is covered with polyps. Leiopathes corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that they are not necessarily now threatened with extinction now but that may become so unless trade is closely controlled. Gerardia species are sometimes known as False Black Corals. Not all of these are deep sea: colonies are found in the Mediterranean between 50 and 80 m.

Journal References:
E. Brendan Roark, Thomas P. Guilderson, Robert B. Dunbar, Stewart J. Fallon, and David A. Mucciarone. Extreme longevity in proteinaceous deep-sea corals. PNAS 2009 : 0810875106v1-pnas.0810875106.

E. Brendan Roark, Thomas P. Guilderson, Robert B. Dunbar and B. Lynn Ingram. Radiocarbon-based ages and growth rates of
Hawaiian deep-sea corals. MARINE ECOLOGY PROGRESS SERIES, Vol. 327: 1–14, 2006

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