SYNCHRONOUS FLUORESCENCE-SPECTRA OF DISSOLVED ORGANIC-MATTER (DOM) OF ALGAL ORIGIN IN MARINE COASTAL WATERS

Naturally occurring dissolved organic matter (DOM) was investigated in a lagoonal system with the aim to study the origin and mixing of the DOM components. Water samples were collected in the Sacca di Goro lagoon (Po river delta, Italy) and analysed by means of different techniques, such as fluorescence, absorption and dissolved organic carbon (DOG) measurements. Synchronous fluorescence spectra obtained from both laboratory algal cultures and benthic macroalgae collected in situ were compared with spectra from field samples in order to distinguish DOM components having autochthonous (algal) origin with respect to remote formation. Two main components could be identified on the basis of their synchronous fluorescent bands. The results indicated that the first band (band hA at lambda = 275 nm), prevailing in seawater samples, could reflect a recent biological production, while the second (bands hB and hC at lambda > 300 nm) prevailing in the tributaries water samples, could likely be due to older or remote formation. The synchronous peak height ratio hA:hB is proposed as an useful parameter describing the different contribution and mixing of the DOM components present in the lagoonal-estuarine waters.