SESAME 2008 Spring Mediterranean Oceanographic Campaign: LIF determination of CDOM and phytoplankton distribution

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. Along the cruise detailed chemical and physical determinations have been performed in the already scheduled 18 stations. Here we will focus the interest of the communication, only in the measurement performed with the lidar fluorosensor apparatus.
The mobile laboratory, installed on the R/V Urania, has allowed for a semi-automatic continuous remote monitoring of surface seawater quality and phytoplankton content during the SESAME campaign. Thanks to narrowband filtering and electronic gating, LIF signals do not need corrections for radiometric and spectral characteristics of solar irradiance and surface reflectance. Furthermore, due to the short distance from the target, atmospheric effects are negligible. The different Lidar LIF detection channels are simultaneously stored and successively analyzed including ancillary information. Calibration on specific fluorescence channels has been obtained comparing the contemporary determinations performed with the portable fluorometer.
The lidar fluorosensor produced thematic maps of different surface sea water constituents, releasing depth integrated chlorophyll content (0-10m), and integrated DOM content (0-20m) over the investigated area. In particular, a large bloom with a spatial extension of 200 km has been observed along the northern transect, similar to the bloom in the coastal area transect and more restricted but well defined two algal patches along the transfer from Balearic islands to the coast of Spain.