Resource partitioning by reef corals as determined from stable isotope composition |
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Authors: | L Muscatine J W Porter I R Kaplan |
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Institution: | (1) Department of Biology, University of California, 90024 Los Angeles, California, USA;(2) Department of Biology, University of Georgia, 30602 Athens, Georgia, USA;(3) Institute of Geophysics and Planetary Physics, University of California, 90024 Los Angeles, California, USA |
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Abstract: | The pattern of resource partitioning vs depth by corals collected in February 1983 from Jamaica and the Red Sea was determined from their stable carbon isotope composition. Observations were made on isolated zooxanthellae and corresponding algae-free animal tissue from eight species at four depths over a 50 m bathymetric range. Zooxanthellae 13C was high in shallow water and became lower as depth increased. This trend correlated significantly with the anual integrated photosynthetic rate. The trend is interpreted according to a depletion-diffusion hypothesis; in shallow water, at high rates of photosynthesis, metabolic CO2 is nearly depleted and the supply of CO2 from seawater bicarbonate is limited by diffusion. Since most of the available CO2 is fixed, isotope fractionation is minimal. In deeper water, at lower rates of photosynthesis, metabolic CO2 is ample, and isotope fractionation is greater. Animal tissue 13C was slightly lower than corresponding zooxanthellae values in shallow water. As depth increased the difference between zooxanthellae and animal tissue 13C increased and the latter approached the 13C of oceanic particulate organic carbon. These data suggest that carbon is translocated at all depths and that deep-water corals draw significantly on allocthonous sources of carbon.Contribution No. 436 of the Discovery Bay Marine Laboratory of the University of the West Indies |
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