Fluorescence Excitation and Emission Spectra of Dissolved Organic Matter in Sea Water

Fluorescence spectra of waters from the Sargasso Sea, the Atlantic Shelf, a Trichodesmium “bloom,” and a cultured concentrate of suspended matter were obtained on board R/V Chain with the Baird-Atomic fluorescence spectrophotometer. Excitation (peaks at 282 mμ and 365 mμ) and emission (peaks at 350 mμ and 450 mμ) spectra of water from the Trichodesmium bloom were well defined, suggesting that specific sources of fluorescence may be identifiable after recent biological events. Spectra of several samples from the surface showed recurring peaks at 340 mμ, suggesting that fluorophors may concentrate at this interface. Within the limits of sensitivity of this instrument, no spectra were seen for water from the Sargasso Sea. Spectra of water from the Atlantic Shelf were very broad, with an emission peak ranging from 410 mμ to 430 mμ. A remarkable similarity was seen in the emission (peaks at 340 mμ and 450 mμ) of dissolved materials in a laboratory culture of Skeletonema costatum and an incubated concentrate of suspended matter in surface water from the shelf.