Combining in situ and multi-sensor satellite data to assess the impact of atmospheric deposition in Lake Garda

In this study we investigated the effect of the deposition of Saharan dust on the phytoplankton growth (i.e. dust fertilization hypothesis) in Lake Garda, an oligotrophic basin with low nutrient and low chlorophyll-a (chl-a) concentration, by combining satellite data with in situ measurements. A Saharan dust event has been recognised on 28/07/2005 by: (i) SEVIRI (Spinning Enhanced Visible and InfraRed Imager) data processing, (ii) a significant increase of PM10 with respect to PM2.5 in a site southern the lake; and (iii) the high values of AOT (aerosol optical thickness) with corresponding low values of the Angstrom parameter measured by AERONET in Ispra. Few days later, an increase of chl-a in the lake was detected from MERIS (Medium Resolution Imaging Spectrometer). The images were processed with the Case-2 Regional (C2R) processor that provided values comparable to in situ measurements (r=0.78). Therefore, preliminary results seem to indicate a response of the Lake Garda in terms of increasing of chl-a as a consequence of the Saharan dust event recognised on 28/07/2005. Nevertheless, the analysis of further events is mandatory in order to have confirmation (or no), about the linkage between atmospheric deposition and phytoplankton dynamics in the study area.