CYANOBACTERIA ASSESSMENT IN I TALIAN AND S WEDISH WATERS FROM SPACE

Cyan-IS-Was was based on the collaboration between the CNR-IREA in Milan and the University of Stockholm, which over the years of the project have shared activities of measures in situ, processing of satellite data and ecological analysis. In order to respond to the aims of the project, other research Italian and Swedish bodies were involved in various activities. For instance, in situ measurement were carried out with the technical and scientific collaboration of the CNR-ISMAR of Venice and of the LUODE consulting in Stockholm; processing data from Earth Observation (EO) implied the participation of the CNR-ISSIA researchers of Bari and of the Brockman Geomatics Sweden, while for ecological analysis Cyan-IS-was partners collaborated with the University of Parma and the CNR-ISE of Pallanza and Klaipėda University Coastal Research and Planning Institute. Stockholm University has been strongly cooperating with Bio-Optika, UK, which supported the CyanIsWas field work in lake Vänern. Abstract: We present a band ratio algorithm based on remote sensing reflectance (RRS) data to detect an algal bloom composed of cyanobacteria ( Planktothrix spp.) and chrysophytes in Lake Idro, a small meso-eutrophic lake situated in the subalpine region (northern Italy). The bloom started around the first week of September 2010 and persisted for about 1 month, with highest mean chlorophyll-a concentrations (17.5±1.6 mgm −3 ) and phytoplankton cellular density (7,250,000 cell · l −1 ) measured on September 14, 2010. RRS data obtained from in situ measurements were first investigated to select the diagnostic wavelengths (i.e., 560 and 620 nm) of both phycoerythrin (present in the Planktothrix spp.) and other pigments (e.g., fucoxanthin, common to several species of chrysophyte). Testing the algorithm on RRS data derived from atmospherically corrected image data showed the ability of the medium resolution imaging spectrometer (MERIS) to detect the bloom also. The results demonstrate that a combination of in situ and MERIS data is a valuable tool to monitor the extent and duration of phytoplankton blooms. Abstract : Lake Omodeo is the largest artificial reservoir of Sardinia and its waters are a valuable resource for irrigation, domestic and industrial purposes. Lake Omodeo has serious problems of eutrophication. Since 2007 the local water authority has been undertaken a monitoring program designed to test an integrated methodology based on field measurements and remote sensing. This study illustrates the production of multitemporal spatialised maps of chlorophyll-a concentrations from satellite data acquired from Medium Resolution Imaging Spectrometer (MERIS). The analysis confirmed the eutrophic status of Omodeo, especially between spring and summer (mainly due to cyanobacteria bloom) assessing their dependency on weather conditions and river inputs. Abstract : BOMBER (Bio-Optical Model Based tool for Estimating water quality and bottom properties from Remote sensing images) is a software package for simultaneous retrieval of the optical properties of water column and bottom from remotely sensed imagery, which makes use of bio-optical models for optically deep and optically shallow waters. Several menus allow the user to choose the model type, to specify the input and output files, and to set all of the variables involved in the model parameterization and inversion. The optimization technique allows the user to retrieve the maps of chlorophyll concentration, suspended particulate matter concentration, coloured dissolved organic matter absorption and, in case of shallow waters, bottom depth and distributions of up to three different types of substrate, defined by the user according to their albedo. The software requires input image data that must be atmospherically corrected to remote sensing reflectance values. For both deep and shallow water models, a map of the relative error involved in the inversion procedure is also given. The tool was originally intended to estimate water quality in lakes; however thanks to its general design, it can be applied to any other aquatic environments (e.g., coastal zones, estuaries, lagoons) for which remote sensing reflectance values are known. BOMBER is fully programmed in IDL (Interactive Data Language) and uses IDL widgets as graphical user interface. It runs as an add-on tool for the ENVI+IDL image processing software and is available on request. column and bottom from remotely sensed imagery. - The tool implements an optimization technique to invert a bio-optical model for deep and shallow waters. - The software is programmed in IDL and runs as an add-on tool for the image processing software the ENVI+IDL. - A series of GUIs allow the user to parameterize the bio-optical model and to run the inversion. Abstract : Optical close-range instruments can be applied to derive water quality parameters for monitoring purposes and for validation of optical satellite data. In situ radiometers are often difficult to deploy, especially from a small boat or a remote location. The water insight spectrometer (WISP-3) is a new hand-held radiometer for monitoring water quality, which automatically performs measurements with three radiometers (Lsky, Ed) The instrument is described and its performance is assessed by an intercomparison to well-known radiometers, under real fieldwork conditions using a small boat and with sometimes windy and cloudy weather. Root mean squared percentage errors relative to those of the TriOS system were generally between 20% and 30% for remote sensing reflection, which was comparable to those of the other instruments included in this study. From this assessment, it can be stated that for the tested conditions, the WISP-3 can be used to obtain reflection spectra with accuracies in the same range as well-known instruments. When tuned with suitable regional algorithms, it can be used for quick scans for water quality monitoring of Chl, SPM, and aCDOM. Abstract : The Curonian Lagoon, the largest in Europe (total surface area 1584 km 2 ), is located in the southern part of the Baltic Sea, from which it is separated by a narrow sand bar and to which it is connected by the Klaipeda Straits. It is characterised by shallow eutrophic waters (mean depth 3.8 m) with average low salinity (<5‰) due to the nutrient-rich freshwaters discharged by the river Nemunas. Cyanobacteria blooms, including species producing toxic metabolites, have been a frequent phenomenon in summer. In this study a series of MERIS Full Resolution (FR) satellite images acquired between 2004 and 2009 during summer periods were used to assess the temporal evolution and spatial variability of the lagoon water quality in terms of chlorophyll-a. The models/ algorithms were calibrated/validated with field data collected in 2009, based on in situ radiometric (remote sensing reflectance -Rrs-) and limnological (chlorophyll-a concentrations - chl-a-) measurements. The chl-a concentrations were estimated by developing a semi-empirical band ratio (Rrs(708)/Rrs (664)) equation applied to MERIS images after correction for atmospheric effects with the 6S code. Results from this study suggest elevated spatial and temporal variability of chl-a. Spatial variability probably arises from the mosaic of situations within the Curonian lagoon in terms of bottom sediment features, nutrient availability in the water column, water depth and hydrodynamics. Temporal variability is probably linked to complex and interplaying metereological and environmental constraints such as the length of the ice cover period, average water temperatures, wind-induced sediment resuspension, the pattern of precipitations and river-associated nutrient transport to the lagoon. This study stresses the importance of remote sensing as a valid tool for long-term whole ecosystem studies. The preliminary results need more through analyses and intersection with other environmental data in order to better comprehend algal bloom determinants in complex and extremely dynamic systems such as coastal lagoons. Abstract: Shallow eutrophic lakes display unpredictable patterns of phytoplankton growth, distribution, vertical and horizontal migration, likely depending on environmental conditions. Chlorophyll-a (Chl-a) monitoring provides reliable information on primary producer dynamics if monitored frequently. We present a practical approach which allows monitoring Chl-a in continuos with a radiometric system that measures water optical spectral properties. We tested this method in a shallow, nutrient rich lake in northern Italy, the Mantua Superior Lake, where the radiometric system collected data daily (i.e., every five-minutes), for about 30 days. Here, specifically developed algorithms were used to convert water reflectance to Chl-a concentration. The best performing algorithm (R 2 =0.863) was applied to the larger dataset collected in September 2011. We characterized intra- and inter-daily Chl-a concentration dynamics and observed a high variability: in a single day Chl-a varied from 20 to 130 mg m -3 . Chl-a concentration values were correlated to meteo-climatic parameters, showing that solar radiance and wind speed are key factors regulating the daily phytoplankton growth and dynamics. Such patterns are usually determined by vertical migration of different phytoplankton species within the water column as well as by metabolic adaptations to changes in light conditions. Abstract: This letter focuses on water-quality estimation in the northern Adriatic Sea using physically-based methods applied to image obtained with the Hyperspectral Imager for the Coastal Ocean (HICO TM ). Optical properties of atmosphere and water were synchronously measured to parameterise such methods. HICO TM derived maps of chlorophyll-a (chl-a) and suspended particulate matter (SPM) indicated low values, in the range of 0–3 mg m −3 and 0–4 g m −3 , respectively, correlating significantly with field data (R 2 = 0