Radiocarbon-based ages and growth rates of Hawaiian deep-sea corals
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The radial growth rates and ages of 3 different groups of Hawaiian deep-sea 'corals' were determined using radiocarbon measurements. Specimens of Corallium secundum, Gerardia sp., and Leiopathes glaberrima were collected from 450 40 m depth at the Makapuu deep-sea coral bed off the southeast coast of Oahu, Hawaii, USA, using a submersible vessel (PISCES V). Specimens of Antipathes dichotoma were collected at 50 m depth off Lahaina, Maui, Hawaii. The primary source of carbon to the calcitic C. secundum skeleton is in situ dissolved inorganic carbon (DIC). Using 'bomb 14C' time markers we calculated radial growth rates of -170 m yr-1 and ages of 67 to 71 yr for specimens of C. secundum up to 28 cm tall. Gerardia sp., A. dichotoma, and L. glaberrima have proteinaceous skeletons, and labile particulate organic carbon (POC) is their primary source of architectural carbon. Using 14C we calculated a radial growth rate of 15 m yr-1 and an age of 807 30 yr for a live collected Gerardia sp., showing that these organisms are extremely long lived. Radiocarbon measurements taken from the inner and outer portions of basal cross sections of 4 sub-fossil Gerardia sp. samples showed growth rates (range 14 to 45 m yr-1) and ages (range 450 to 2742 yr) similar to that of the live collected sample. Similarly, with a growth rate of < 10 m yr-1 and an age of 2377 yr, L. glaberrima at the Makapuu coral bed is also extremely long lived. In contrast, the shallow-collected A. dichotoma samples yielded growth rates ranging from 130 to 1140 m yr-1 (12 to 32 yr). These results show that Hawaiian deep-sea corals grow more slowly and are older than previously thought. Inter-Research 2006.