Dissolved organic matter (DOM) cycling in coral reefs: Compositional constraints

Abstract

The sea hosts one of the largest carbon pools in the world and most carbon is present as DOC. The DOC pool is highly dynamic due to biological activity and large parts of labile DOC are introduced into the food chain via the microbial loop. Recent studies have found that important reef organisms, corals and sponges, also take up and assimilate DOC as a large part of their diet. This underlines the importance of DOC in the energy budget of coral reefs. It was shown that most DOC produced on coral reefs is highly labile and can be taken up within hours to several minutes. This high turnover complicates the characterization of the labile DOC. Adding to that is the complexity of the coral and sponge holobiont. Even if specific parts of the DOM pool could be characterized, it would be hard to distinguish exact sources or sinks of the organic matter from different parts of the holobiont. Most analytical techniques used for DOM are relatively new and unfortunately information on DOM fluxes and especially composition is still sorely lacking. With this study we plan to investigate (1) the chemical composition of the labile part of DOC used as an energy carrier on coral reefs (2) which compounds are released by different types of reef organisms (3) if these compounds are representative of that type of organism or species specific (4) which other organisms may assimilate this DOC.