Ecological Impacts of Sponge Metabolism on Benthic Marine Communities
Niels Lindquist, Institute of Marine Science, University of North Carolina, Chapel Hill
16 Mar 2007
Sponges (phylum Porifera) are major contributors to organic matter and nutrient element cycling in diverse marine ecosystems. Their great abundance and biomass, combined with their exceptional capacities to pump and filter up to 100,000 times their own volumes each day and to efficiently clear seawater of small plankton, including bacteria and viruses, allow them to significantly alter concentrations of particulate organic matter (POM) in surrounding waters. Further, many sponge species host massive and diverse communities of autotrophic and heterotrophic microorganisms potentially giving these high microbial abundance (HMA) sponges the ability to also utilize dissolved organic matter (DOM) and nutrient elements in seawater and to broadly affect the balance among biogeochemical cycles of carbon (C), nitrogen (N) and other elements critical to the productivity and sustained health of many benthic marine communities. Emerging data on rates of sponge mediated particulate and dissolved organic matter cycling indicate that sponges can be responsible for tremendous net fluxes of dissolved inorganic nitrogen (DIN) to reef environments. This DIN likely accelerates the growth of reef macroalgae, and possibly that of pathogenic coral epizootics. Sponge and seaweed exudation of dissolved organic matter, including noxious secondary metabolites, potentially creates a "toxic" environment that further increases stress on corals. A quantitative assessment of sponge contributions to biogeochemical cycles of diverse benthic communities and overlying waters is needed given that eutrophication, climate warming, and overfishing can create conditions that increase, or in some critical ecosystems, decrease, sponge abundance. My talk will focus on the results of our in situ examinations of sponge metabolism using state-of-the-art instrumentation and the potential impacts of sponges on benthic and coupled pelagic communities.