Award: OCE-1929293

Ecological theory predicts that high biodiversity in crowded, nutrient-limited systems like coral reefs may be driven by niche partitioning. In these systems, the successful coexistence of species may therefore be facilitated by adaptations that allow individualspecies to exploit novel sources of nutrients. In sponge communities on Caribbean coral reefs, there is substantialspecificity in the abundance, diversity, and composition of microbial symbionts (microbiomes) across coexisting sponge species, and these symbiontsexpandthe metabolic capabilitiesof their hosts by allowing sponges to access novel nutrient pools.This project tested the hypothesis that these interactions allow host species to partition available sources of nutrients. To test this hypothesis, we conducted work in Panama and the Florida Keys that included in situ experiments to assess the removal of particulate (bacteria and phytoplankton) and dissolved (sugars and amino acids) organic matter and ex situ experiments to assess the capacity of sponge microbiomes to take up inorganic sources of carbon and nitrogen. Our results demonstrate that the ten most ecologically dominant sponges on Caribbean reefs each have unique contributions to the cycling of organic matter and nutrients on these reefs. The ability of these species to utilize unique resource pools is intimately linked to their interactions with microbial symbionts. These results contribute to our understanding of links between biodiversity (both in terms of microbial symbiont and sponge host) and ecosystem functioning on coral reefs and generate new hypotheses pertaining to the ecologicalsuccess of sponges on Caribbean reefs. This project also provided graduate and undergraduate students with field and lab experience and trained 11 international students in a field course in sponge ecology and taxonomy in Panama. Last Modified: 12/12/2024 Submitted by: ChristopherJFreeman