Seminar: Dr. Steve Skrabal, UNC Wilmington

The Photochemistry of Resuspendable Sediments and Its Importance to the Cycling of Metals, Nutrients, and Algal Toxins in Coastal Waters (Host: Marc Alperin)

Recent work in our laboratory has addressed the role of photochemically induced release of organic and inorganic nutrients, trace metals, and algal toxins associated with resuspendable sediments in coastal environments. Photorelease of dissolved organic carbon (DOC) and total dissolved copper and vanadium have been observed in sediments from diverse biogeochemical settings, after modest irradiation times (equivalent of 1 day) and using environmentally relevant suspended sediment concentrations (40-300 mg/L). Nutrients such as dissolved phosphate and dissolved organic nitrogen can also be photoreleased from estuarine sediments, including sterilized controls, suggesting that a true photolytic mechanism is likely operating. The photochemical reactivity of sediments, with respect to DOC and potentially other substances, appears to be greater in diagenetically unaltered terrestrial material as well as in aged marine algal detritus. Light-induced release of a “red tide” toxin, the brevetoxin PbTx-2, and the freshwater cyanobacterial toxin, microcystin-LR, has been observed less consistently. Such photochemical fluxes represent previously unrecognized sources of biogeochemically relevant substances to overlying waters.