Worldwide, coral reefs are in decline due to local and global stressors. On coral reefs, the removal of algae by herbivores following coral mortality may promote the settlement and growth of corals and prevent dense macro-algal stands. Recent work has shown that herbivorous fish can be surprisingly choosy about the type and density of the algae on which they forage. Increasingly, research with vertebrates and gut-associated microbes has shown that diet can influence the composition of the microbe community and, in turn, gut microbes influence the food choices of vertebrate hosts via several mechanisms. Given the changing “foodscape” of coral reefs, we are interested in whether the gut microbe community in herbivores might explain, in part, their feeding choices. Using a combination of laboratory and field studies in the Bahamas, we tested 3 hypotheses: 1) Does diet influence the composition of the gut microbiota in an aquarium fish model (Gambusia affinis)? 2) Do food availability/habitat influence the composition of the gut microbiota of reef herbivores (Sparisoma viride)? 3) Do herbivorous fish (S. viride) prefer processed algae/agar food that is associated with their own habitat?
Results/Conclusions
Our results support the idea that G. Affinis' gut microbe communities are influenced by diet and that gut microbe communities in S. viride show strong habitat associations. Parrotfish did not show a preference for algae/agar food from their own habitat. Gut microbes are known to influence diet choices in other vertebrates. Given that fish from different habitats have distinct gut microbe communities, this may drive differences in feeding behaviors that are relevant to reef recovery. In future work, we will continue algae feeding experiments using whole algal thalli. We also plan to use molecular techniques that allow us to determine the identity of bacterial OTUs and their relative abundance in fish gut samples to further understand the feedback between habitat, diet, and feeding behavior in reef herbivores.