Metabolomic Analysis of Incurrent and Excurrent Water From Sponges

Sponges are sessile filter-feeders that can process vast amounts of water and are known to influence the chemistry of the surrounding seawater. There has been limited work however to understand the extent to which sponges alter dissolved organic matter (DOM), yet in areas where sponges are abundant, sponges may contribute significantly to the reef seawater profile of DOM. This work provides an in-depth examination of six prevalent sponges on Caribbean reefs and how they alter DOM and other seawater nutrients. Incurrent and excurrent seawater samples were collected for each of the six sponge species and processed for: inorganic nutrients, fluorescent dissolved organic matter (fDOM), untargeted and targeted metabolomics, and particulate matter by flow cytometry. Sponges were sampled from two coral reef sites in the Florida Keys (Florida, USA): Looe Key reef and Wonderland reef in the southern Florida Keys. We found higher that sponges altered a relatively small subset of the DOM profile and were a net sink of most mass features from untargeted metabolomics. However, sponges also released some putatively labile metabolites and processed DOM in a species-specific manner. These results provide additional support for the large impact that sponges have in the dissolved nutrient profile on coral reefs and provide support for a species-specific impact, with some species altering the DOM profile, fDOM profile, and/or inorganic nutrients to a greater extent than other species. These results have implications for better understanding the influence of the sponge community on coral reef nutrient dynamics.