Project: Multi-species interactions on coral reefs: Linking macro-organismal Metabolites to reef processes

Project Abstract:
Chemical interactions between coral reef organisms contribute to the success and biodiversity of economically important coral reef ecosystems. Coral reefs are in crisis worldwide from anthropogenic disturbances and climate change, and understanding of these chemical interactions is important to assess ecosystem health. This project will advance understanding of chemically based, contact-free interactions between benthic organisms (corals, macroalgae, encrusting algae) on coral reefs located within the U.S. territory of the Virgin Islands. The project will produce new knowledge that will help inform coral reef conservation and restoration practices. The knowledge gained will be broadly shared by engaging diverse audiences in appropriate formats, including graduate student education and training of minority undergraduate and outreach to minority middle and high school students. Project findings will be shared through open access manuscripts and publicly accessible press releases and social media posts.

Contact-free chemical interactions between organisms may be a key factor contributing to the success and biodiversity of oligotrophic coral reef ecosystems. Benthic macro-organisms release dissolved organic matter (DOM), comprised of biogenic small molecules (exometabolites), into the water which contribute to the growth of microorganisms and provide settlement and other cues for corals, fish and other organisms. While there is some evidence for these interactions, methodologies to detect and quantify reef extracellular chemicals have largely missed detection of the small, polar molecules which form the majority component of labile DOM that may be critical to reef processes. A new approach was recently developed for marine and now coral reef environments, which opens up opportunities to further understand organismal interactions involving small, polar metabolites on reefs. Here we address this lack of knowledge about labile DOM-mediated interactions on coral reefs. Specifically, we plan to examine if and how macro-organismal species assemblages, representing typical Caribbean reef assemblages from historical (stony coral and crustose coralline algae dominated) and present day (octocoral, macroalgae and invasive crustose algae dominated) reefs collectively contribute to the composition of reef metabolites. Further, we will examine the use of these metabolite pools by reef planktonic and surface-associated microorganisms and settling coral larvae. Specifically, we will measure dissolved metabolite exudates (including polar labile compounds) produced naturally in the field, and by individual and constructed organismal assemblages. Further, we will examine the influence of those metabolites on the growth and traits of microorganisms and on the coral settlement process. This work will produce new hypotheses about specific interactions between reef organisms that may also be applicable to other benthic and ocean ecosystems. Overall, this project will contribute to our understanding of how biodiverse reef ecosystems are built and maintained.