In earlier NSF-funded investigations of nitrogen cycling in sponges, a research team at the University of North Carolina at Chapel Hill demonstrated that sponges play a major role in the N budget of coral reef and other shallow water tropical ecosystems. Their in situ measurements of whole sponge respiration, water pumping rates and chemical fluxes indicate that previous studies based upon enclosure or laboratory experiments seriously underestimate net fluxes and cannot provide data needed to establish actual net fluxes of dissolved inorganic nitrogen (DIN) and other N species. Marine sponges strongly affect N cycling in coastal environments through pumping and filtering tremendous volumes of water while their hosted microorganisms affect a wide range of N transformations, including nitrification and dissolved and particulate organic nitrogen uptake and degradation, and potentially N2 fixation and denitrification, thereby adding or subtracting bioavailable N from coastal systems. Sponge DIN flux to overlying waters at Conch Reef, Florida Keys, is larger than any other benthic N source as should be the case for all coastal systems where sponges are abundant.
With additional funding under this award, the UNC team will be joined by biogeochemical colleagues at the University of Hawaii in an effort he to quantify sponge impacts on coastal N cycles by (i) using in situ methodologies to construct accurate N budgets for sponges that will identify them as nutrient sources or sinks, and (ii) investigating environmental controls over sponge mediated N transformations. The net impact of sponges on biogeochemical N cycling in coastal environments is largely unknown. This new work will be the first to use in situ methods to quantify the nitrogen cycling in sponges and the resultant fluxes of DIN and DON from sponges.
The project will have a number of broader impacts. The information gained in this study, although directly applicable to a subset of sponge species, will have broad implications for nitrogen biogeochemistry in coastal ecosystems with abundant sponges. A graduate and several undergraduate students will learn in both laboratory and field settings a spectrum of state-of-the-art techniques and instrumentation firsthand and, when the results are ultimately synthesized for publication, will benefit from participation in the exchange of ideas with established researchers from diverse fields. The University of Hawaii is a designated EPSCoR institution and a federally recognized minority serving institution, thus students from underrepresented groups are likely to be included as participants in the proposed research and will benefit from education activities stemming from the results of this research. Finally, using the University of North Carolina's established connections with Earth Eco International (Phillipe Cousteau, President) and the Science Under the Sea, educational projects, significant public outreach efforts will result including live web-based videoconferences from AQUARIUS with high school and middle school students across the country.
