Award: OCE-1756249

Marine sponges are common inhabitants of coastal areas around the world and have high diversity on coral reefs, mangrove estuaries, and rocky shores. Earlier work on sponges established that their well-developed aquiferous system allows for efficient filter-feeding on particulate organic matter, including planktonic algae and bacteria. More recent work determined that sponges can host microbial symbionts that can supplement host feeding with the consumption of dissolved organic carbon and the products of photosynthesis. Recent investigations established that each sponge species hosts a unique community of microbial symbionts and raised the question of whether these unique communities support unique modes of feeding and resource use in their hosts. In ecology and evolutionary biology, this phenomenon is termed niche partitioning, whereby natural selection favors species that evolve different patterns of resource use or different niches. In this project, we investigated whether Caribbean sponges provide an example of niche partitioning mediated by microbial symbionts. We (1) used stable isotopes of carbon and nitrogen to track measure the contribution of microbial symbionts to host metabolism; (2) quantified the ability of sponges to remove particulate and dissolved carbon and nitrogen from the surrounding water; and (3) quantified sponge-associated microbiomes to examine the links between symbiont community structure and host metabolism. Our data indicate that sponges have variable rates of heterotrophic filter feeding, with some species removing much less bacteria than others. Analyses of carbon and nitrogen stable isotopes and quantification of particulate and dissolved carbon uptake are continuing in the laboratories of the collaborative investigators associated with this project. During this project, we discovered that what was once known as a single species, Ircinia felix, contains a very closely related group of seven species. Each of these species has a unique morphology and can be identified in the field; each species also hosts a unique community of bacteria that provide the host with access to a unique suite of metabolic capabilities. We provided scientific descriptions and taxonomic names for these six new members of the genus Ircinia. Furthermore, 424 metagenome-assembled genomes (MAGs) were constructed from 10 Ircinia species, providing a dense, publicly available dataset to serve as a foundation for future research on sponge-microbe interactions. This project trained 6 undergraduate and 5 graduate students at Stony Brook University. In addition, this project sponsored a course to train graduate students in sponge ecology, taxonomy, and systematics at the Smithsonian Tropical Research Institute’s Bocas del Toro Research Station in Panama. Participants included 13 students (8 from the USA), the 4 collaborative investigators of this project, and 4 additional instructors. The course included an introduction to metazoan systematics, general taxonomy of Porifera to the family level, identification of common species of Bocas del Toro and the Caribbean, ecology of sponge-microbe associations, cellular biology of sponges, chemical ecology and metabolomics, infaunal associations, field surveys of sponge communities, and student-designed independent projects. Last Modified: 10/28/2022 Submitted by: Robert W Thacker