The natural release of amino acids from the symbiotic coral Heteroxenia fuscescens (Ehrb.) as a function of photosynthesis

Amino acid release from colonies of the symbiotic soft coral Heteroxenia fuscescens (Ehrb.) was studied as a function of photosynthesis. The rate of net DFAA release averaged 1 μmol·100 mg −1 autozooid dw·h −1 indicating that de novo synthesis by the zooxanthellae exceeds the demand of both symbionts and host. The dark release corresponded to 1–2% of the light rate. In nutrient poor environments, such as tropical reefs, surplus production of dissolved organic compounds could be of trophic importance for other auto- and heterotrophic organisms. In calculating the amount of organic C transferred from zooxanthellae to the host, it has to be taken into account that surplus as asimilates are not necessarily utilized by the host.