SESAME 2008 Spring Mediterranean Oceanographic Campaign: in-situ determination of fluorescence dissolved and particulated organic matter

Within the frame of the European project SESAME (Southern European Seas Assessing and Modelling Ecosystem changes), the ENEA leaser remote sensing laboratory has been invited to join the Mediterranean oceanographic campaign deploying two instruments on board of the R/V URANIA, a remote sensing lidar fluorosensor apparatus and a portable laser fluorometer (Casper).
Among the seven marine areas of interest for the project, we took part to the investigation of North Western Mediterranean shelf ecosystem, of high relevance for the presence of different trophic regimes. The oceanographic campaign was carried on board of the R/V Urania, starting March 26th from Trapani in Sicily and concluded April 7th 2008 with the arrival to the Livorno harbor. Here we will focus the interest of the communication to the measurement performed with Casper fluorometer during the campaign.
The compact instrument allows for a dual laser excitation of sea water samples in the UV (266 nm) and Visible (405 nm) spectral region in order to match the fluorescence analysis of dissolved (protein like compounds, humic acids) and particulate (phytoplankton) organic matter. Furthermore, a double filtration in the hydraulic feeding circuit, is included in order to better discriminate between fluorescence contribution of dissolved components from overlapping phytoplanktonic pigments.
During the SESAME campaign, seawater samples were collected from the surface up to depths of 2800m using a CTD/rosette system equipped with Niskin bottles in all the scheduled stations.
Fluorescence data, after proper spectral deconvolution, were calibrated with contemporary on board instruments and released in absolute values. Tyrosine and Tryptophan protein-like components, CDOM, carotenoids, phycoerythrin, phycocyanin and Chl-a content have been the main contributors extracted from the spectra. Depth and superficial distribution of the previous components have been obtained as well as a detailed statistical analysis implemented. These information will be also used as database for the development of regional bio-optical algorithms for radiance satellite radiometers calibration.