Gattuso J.-P., Yellowlees D. & Lesser M., 1993. Depth- and light-dependent variation in carbon partitioning and utilization in the zooxanthellate coral Stylophora pistillata. Marine Ecology Progress Series 92: 267-276.



Abstract

This study investigated the effect of light on the short-term metabolic fate of 14C-bicarbonate in zooxanthellae and animal tissue of the coral Stylophora pistillata (Esper, 1797) and on the specific activity of host enzymes involved in the metabolism of carbon. Short-term incubations of coral colonies were carried out in situ at Bowl Reef (Great Barrier Reef, Australia) at depths of 5 and 30 m to measure rates of oxygen production and consumption and rates of 14C fixation. Short-term 14C incubation experiments were also carried out under controlled conditions in the laboratory. Additional samples were collected from 5, 10, 15 and 20 m at Chicken Reef (GBR) to determine the specific enzyme activity of coral tissues from different depths in the water column. Light and depth both affected the distribution of 14C among photosynthetic products but neither affected translocation rate measured by the in vivo method (60.4 %). The majority of the 14C label was recovered in lipid (33-94 %) and water-soluble fractions (5-67 %). The zooxanthellae incorporated more 14C into lipids than into water-soluble compounds (88-94 % vs 4-7 %) while the animal exhibited higher 14C levels in water-soluble compounds than in lipids (44-67 % vs 33-56 %). Algal fractions showed decreased 14C incorporation into lipids and increased 14C incorporation into water-soluble compounds with increasing depth or decreasing irradiance. The specific activity of 3-hydroxyacyl CoA dehydrogenase increased with depth supporting the hypothesis that lipids are being catabolized more rapidly at greater depths. Citrate synthase and hexokinase activities also decreased with depth. The decrease in cytochrome oxidase activity with depth is consistent with a concomitant decrease in respiration as depth increases. These results confirm that the carbon cycling in S. pistillata is partially dependent on light.


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