Bacterial decomposition of coral mucus as evaluated by long-term and quantitative observation
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Coral mucus released from Acropora formosa and Montipora digitata was incubated with bacteria under dark conditions for 1 year to evaluate the quantitative degradability. All the mucus samples showed a similar decomposition pattern: about 80% of total organic carbon (TOC) in the mucus was mineralized within 1 month, while some mucus was slowly decomposed over the 1 year. Regression analysis using an exponential curve considering three degradability pools (labile, semilabile, and refractory) fitted the changes of the TOC concentrations very well (r 2 > 0.99). Compiling the data on the two coral species, the labile organic C in the coral mucus had mineralization rates of 10–18% d−1 and accounted for 79–87% of the initial TOC in the mucus. Semilabile organic C had mineralization rates of 0.3−1.6% d−1 and accounted for 11−18% of the initial TOC. Refractory organic C accounted for 6% at most. These results suggest that not all coral mucus is rapidly decomposed by bacteria but some mucus remains as semilabile and refractory organic matter for several months.
KeywordsCoral mucus Mineralization Bacteria Coral reef Refractory organic matter
We are grateful to K. Shimada (The University of Tokyo), A. Suzuki (National Institute of Advanced Industrial Science and Technology), K. Sakai (University of the Ryukyus), R. Iguchi (University of the Ryukyus), and R. Suwa (University of the Ryukyus) for the experimental setup and technical assistance. We are also grateful to anonymous reviewers and M. Warner (topic editor) who provided many helpful comments to improve the manuscript. This study was financially supported by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists.
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