Effect of water currents on organic matter release by two scleractinian corals

Organic matter release by scleractinian corals fulfils an important ecological role as energy carrier and particle trap in reef ecosystems, but the hypothetically stimulating impact of water currents, an essential and ubiquitous environmental factor in coral reefs, on this process has not been investigated yet. This study therefore quantifies organic matter release by two species of scleractinian corals subjected to ambient water current velocities ranging from 4 to 16?cm?s^?1 using closed-system flow-through chambers. Findings revealed that particulate organic matter (POM) concentration was significantly increased in the flow-through chambers in all investigated coral species compared to still water conditions, while no effect on dissolved organic carbon (DOC) concentration could be observed. These results suggest that POM release by corals may be controlled by hydro-mechanical impacts, while DOC fluxes are rather influenced by the physiological condition of the corals. Hence, this study indicates that previous POM release quantification results are conservative estimates and may have underestimated in situ POM release through corals in reef environments. The contribution of coral-derived POM to biogeochemical cycles in reef ecosystems, therefore, may be more pronounced than already assumed.