Sponge Coral Picoplankton Incubation Experiment

Exudates from corals and algae have been shown to support predominantly autotrophic or heterotrophic microbial communities in the overlying seawater respectively. However, there is no information on how sponges, which filter vast amounts of water on the reef, influence the seawater microbial community composition. Here, we incubated coral reef surface water picoplankton communities (filter at 1.6 um) with filtered (0.2 um) sponge exhalent water or reef surface water as medium. The bottle incubations were conducted in the dark for 48 hours and seawater was sampled for nutrients and microbial composition at the beginning (T0), 24 hrs (T24) for microbial composition only, and at the end (T48). The microbial communities started out very similar to each other and then diverged at 24 and 48 hours. There was a relative increase in heterotrophic bacteria in the sponge exhalent treatment compared to the reef seawater treatment, but these were different from many of the opportunistic pathogens described with previous algal incubations.