Resolving DOM fluorescence fractions during a bloom patch on the Southwest Florida Shelf.

Organic matter can be supplied naturally from land through rivers or produced in the marine environment. Current methods of examining natural bulk dissolved organic matter (DOM) are not able to discriminate multiple sources of DOM. A diagnostic tool to identify DOM sources is critical to determine possible sources of organic nutrients that influence harmful algal bloom (HAB) development. This study applied multi-wavelength fluorescence coupled with a supervised pattern recognition technique (e.g., parallel factorial analysis (PARAFAC) using samples collected from river, estuary and shelf waters where the toxic dinoflagellate off of Sanibel Island, Florida was observed. The PARAFAC model distinguished four different fractions of DOM components containing humic-like and protein-like components. The derived terrestrial humic-like material was indicative of land-based sources while the tryptophan-like component was likely produced from biological production. The study developed and tested the hypothesis that the direct relationship of the protein-like DOM fluorescence with density indicated that the bloom patch was most likely supported by organic nutrients produced . The results demonstrated that multi-wavelength fluorescence analysis coupled with PARAFAC modeling technique simultaneously resolved DOM fluorescence fractions and their possible sources-information that are critical in explaining harmful algal bloom formation.