POSEIDON system: Environmental monitoring with new generation optical instruments

The Poseidon monitoring and forecasting system for the Hellenic Seas has entered its second phase. During this stage, currently under implementation, among other improvements a new generation of optical instruments has been scheduled to be installed and some of them are already operational. These instruments monitor (a) apparent optical properties-AOPs: surface incident irradiance at seven wavelengths, water leaving radiance at seven wavelengths, broadband scalar irradiance (PAR) at four depths; (b) Inherent optical properties-IOPs: hyperspectral beam attenuation and absorption throughout the visible at 80 wavelengths with a 4nm resolution, turbidity (back scattering at 140deg) at four depths; (c) chlorophyll-a fluorescence at four depths. This paper describes in detail the instruments selected and installed and discusses calibration and bio-fouling issues. Furthermore it presents data observed during five months of operation in the Cretan Sea.