MEPS 442:87-99 (2011)  -  doi:10.3354/meps09400

Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos

Ronald E. Thresher1,*, Bronte Tilbrook2, Stewart Fallon3, Nick C. Wilson4, Jess Adkins5

1CSIRO Climate Adaptation Flagship, GPO Box 1538, Hobart, Tasmania 7001, Australia
2CSIRO Wealth from Oceans Flagship and Antarctic Climate and Ecosystem Co-operative Research Centre, Hobart, Tasmania 7001, Australia
3Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia
4CSIRO Process Science Engineering, Clayton, Victoria 3169, Australia
5California Institute of Technology, Pasadena, California 91125, USA

ABSTRACT: Ocean acidification has been predicted to reduce the ability of marine organisms to produce carbonate skeletons, threatening their long-term viability and severely impacting marine ecosystems. Corals, as ecosystem engineers, have been identified as particularly vulnerable and important. To determine the sensitivity of corals and allied taxa to long-term exposure to very low carbonate concentrations, we examined the distribution and skeletal characteristics of coral taxa along a natural deep-sea concentration gradient on seamounts of SW Australia. Carbonate under-saturation had little evident effect on the depth distribution, growth or skeletal composition of live scleractinians or gorgonians, with corals growing, often abundantly, in waters as much as 20 to 30% under-saturated. Developmental anomalies in the deepest skeleton-forming anthozoan collected (an isidid gorgonian, at nearly 4 km depth) suggest an absolute low tolerance limit of about 40% under-saturation. Evidence for an effect of acidification on the accumulation of reef structure is ambiguous, with clear indications of dissolution of high-magnesium calcite (HMC) gorgonian skeletons at depths below 2300 m, but also abundant, old scleractinian skeletons well below the aragonite saturation horizon. The latter might be the result of ferromanganese deposition on exposed skeletons, which, however, may render them inhospitable for benthic organisms.


KEY WORDS: Anthozoa · Echinoderm · Aragonite saturation horizon · Calcite saturation horizon · Gorgonacea · High-magnesium calcite · Mineralogy · Scleractinia


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Cite this article as: Thresher RE, Tilbrook B, Fallon S, Wilson NC, Adkins J (2011) Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos. Mar Ecol Prog Ser 442:87-99

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