Effects of nutrient enrichment on the release of dissolved organic carbon and nitrogen by the scleractinian coral Montipora digitata |
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Authors: | Y Tanaka H Ogawa T Miyajima |
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Institution: | (1) Marine Biogeochemistry Laboratory, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8564, Japan |
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Abstract: | The effects of nutrient enrichment on the release of dissolved organic carbon and nitrogen (DOC and DON, respectively) from
the coral Montipora digitata were investigated in the laboratory. Nitrate (NO3
−) and phosphate (PO4
3−) were supplied to the aquarium to get the final concentrations of 10 and 0.5 μmol l−1, respectively, and the corals were incubated for 8 days. The release rate of DON per unit coral surface area significantly
decreased after the nutrient enrichment, while the release rate of DOC was constant. Because the chlorophyll a (chl a) content of zooxanthellae per unit surface area increased, the release rate of DOC significantly decreased when normalized
to unit chl a. These results suggested that the incorporation of NO3
− and PO4
3− stimulated the synthesis of new cellular components in the coral colonies and consequently, reduced extracellular release
of DOC and DON. Actually, significant increase in N and P contents relative to C content was observed in the coral’s tissue
after the nutrient enrichment. The present study has concluded that inorganic nutrient enrichment not only affects coral-algal
metabolism inside the colony but also affects a microbial community around the coral because the organic matter released from
corals functions as energy carrier in the coral reef ecosystem. |
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Keywords: | |
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