Exopolymer Production by Benthic Diatoms: Rhythms, Responses and Acclimation to Environmental Stress

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0110875Michael Gretz & Graham UnderwoodThe diatoms are among the most important primary producers in the global environment. These single-cell algae are exceedingly abundant and among the most numerous aquatic organisms. The diatoms are major contributors to the base of the marine food chain, upon which economically important marine fisheries and ecologically significant marine mammal and bird populations are dependent. Oceans occupy approximately 70% of our planet and marine microalgae, of which diatoms are a predominant component, exert a powerful influence on today's atmospheric chemistry (they are the primary oxygen producers on earth) and the biogeochemical cycling of carbon and other elements. Hundreds of millions of years of past algal growth has contributed to the important petroleum deposits upon which our modern society depends. Diatoms, both in terms of the organisms themselves and the material they secrete, are of fundamental importance to overall aquatic ecology. Much of the carbon that diatoms fix is secreted in the form of extracellular polymers. These exopolymeric substances (EPS) strongly influence biogeochemical cycling in ecosystems, as they are contributors to the sediment carbon pool, important in food chains and the biostabilization of sediments. This research will characterize the production rates, composition and characteristics of diatom EPS produced by benthic diatoms under various environmental conditions (nutrient limitation, damaging irradiance levels, salinity stress). The composition and structure of different EPS will influence the role such molecules play in the environment. EPS characteristics will be correlated with the changing microenvironment within estuarine diatom biofilms, and with the response of the organisms to important environmental stresses. This information is required to define how diatoms acclimate to the changing conditions within intertidal biofilms and to determine the nature of the different EPS produced, which will lead to further studies of the role of EPS within intertidal biofilms. This work will greatly advance our knowledge of EPS and the physiological conditions in nature that trigger production of different types and may lead to advances in stabilizing sediments or identifying new polymers of commercial interest. In addition, this project will provide a valuable contribution to student training by engaging students in a multidisciplinary effort that involves integrated international cooperation between laboratories in the U.S. and the U.K.