Award: OCE-1756171

Coral reefs harbor an incredible diversity of animal species; however, despite this high biodiversity, they are found in nutrient-poor habitats that are equivalent to marine deserts. High biodiversity is often associated with a division of resources that allows many types of organisms to coexist with minimal competition. Sponges are filter-feeding animals on coral reefs and are both abundant on many reefs in the Caribbean and unique because of their filtration activity. For decades, the success of sponges in the Caribbean has been linked to their filter-feeding ability. However, recent work demonstrated that coexisting sponges on Caribbean reefs host unique communities of bacterial symbionts (long term association with the sponge) and these symbionts might allow sponges to access multiple pools of nutrients that are not available to other organisms. This project tested the hypothesis that common emergent sponge species in the Caribbean have unique nutritional strategies that are mediated by their associations with symbionts that live within the sponge body. Our research combined manipulative field experiments with a novel combination of modern analytical tools and discovered evidence for nutrient resource partitioning across sponge species and uncovered several groups of bacterial symbionts that are likely involved in this resource partitioning. Specifically, we observed that 1) sponge species differed in the dissolved nutrients that they consumed and that they released (e.g., different types of amino acids (the building blocks of proteins), and other more complex molecules that are dissolved in seawater), 2) Some of the observed differences in the consumption or release of nutrients may be influenced by the presence of photosymbionts (similar to having algal symbionts like corals) present in some sponge species, 3) certain dissolved or particulate (bacterial cells) nutrients were taken up in different amounts and retained for different amounts of time across sponge species, and 4) sponges consumed different types of bacterial cells from the water column, showing partitioning of particulate nutritional resources in addition to dissolved nutrients. This work provided the first in-depth analysis of how sponge species meet their nutritional demands in the marine desert of coral reefs which is relevant as we work to conserve these unique ecosystems. This project also trained 10 graduate students and 26 undergraduate students across four institutions, trained an additional 11 graduate students through a sponge ecology workshop, and created outreach materials on sponge nutrient cycling for middle and high school students and for college students. Last Modified: 11/26/2024 Submitted by: CaraFiore