Hyperspectral remote sensing reflectance (Rrs) derived from PRISMA in the visible and infrared range was evaluated for two inland and coastal water sites using above-water in situ reflectance measurements from autonomous hyper- and multispectral radiometer systems. We compared the Level 2D (L2D) surface reflectance, a standard product distributed by the Italian Space Agency (ASI), as well as outputs from ACOLITE/DSF, now adapted for processing of PRISMA imagery. Near-coincident Sentinel-3 OLCI (S3/OLCI) observations were also compared as it is a frequent data source for inland and coastal water remote sensing applications, with a strong calibration and validation record. In situ measurements from two optically diverse sites in Italy, equipped with fixed autonomous hyperspectral radiometer systems, were used: the REmote Sensing for Trasimeno lake Observatory (RESTO), positioned in a shallow and turbid lake in Central Italy, and the Acqua Alta Oceanographic Tower (AAOT), located 15 km offshore from the lagoon of Venice in the Adriatic Sea, which is characterised by clear to moderately turbid waters. 20 PRISMA images were available for the match-up analysis across both sites. Good performance of L2D was found for RESTO, with the lowest relative (Mean Absolute Percentage Difference, MAPD 25\%) and absolute errors (Bias 0.002) in the bands between 500 and 680 nm, with similar performance for ACOLITE. The lowest median and interquartile ranges of spectral angle (SA 8°) denoted a more similar shape to the RESTO in situ data, indicating pigment absorption retrievals should be possible. ACOLITE showed better statistical performance at AAOT compared to L2D, providing R2 0.5, Bias 0.0015 and MAPD 35\%, in the range between 470 and 580 nm, i.e. in the spectral range with highest reflectances. The addition of a SWIR based sun-glint correction to the default atmospheric correction implemented in ACOLITE further improved performance at AAOT, with lower uncertainties and closer spectral similarity to the in situ measurements, suggesting that ACOLITE with glint correction was able to best reproduce the spectral shape of in situ data at AAOT. We found good results for PRISMA Rrs retrieval in our study sites, and hence demonstrated the use of PRISMA for aquatic ecosystem mapping. Further studies are needed to analyse performance in other water bodies, over a wider range of optical properties.
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RBINS Staff Publications 2022
Quantifying and mitigating transboundary effects of anthropogenic activity is a key challenge in environmental management, particularly for wide-ranging species such as large predators, fish and migratory birds, relying on habitats across multiple national jurisdictions. This challenge is especially complex in marine ecosystems, where the movement of species and impacts across borders is largely unobserved. Central-place foragers, such as pinnipeds and seabirds, exemplify this complexity: abundance is typically assessed on local (regional or national) scales on land, yet at-sea movements and drivers of abundance occur on broader transboundary scales. Resolving this mismatch is critical to effective conservation, especially in areas such as the Northwest European Shelf (NWES), which features globally important predator populations (including two pinniped species) alongside growing anthropogenic pressures and a mosaic of national maritime borders. We model an unprecedented GPS dataset from 236 grey (Halichoerus grypus) and 606 harbour seals (Phoca vitulina) tracked in waters of seven countries across the NWES (United Kingdom, Ireland, France, Belgium, Netherlands, Germany and Denmark). Using regional habitat association models, we generate at-sea distribution estimates for both species at 5 km resolution, scaled to haulout counts, producing country-specific and NWES-wide density maps. Analysis of the extent to which seals making foraging trips from one country occupy the Exclusive Economic Zones (EEZs) of other countries revealed substantial transboundary overlap, particularly for grey seals, and harbour seals in the southern North Sea. A case study apportioning grey seal density within three adjacent offshore marine protected areas in different EEZs revealed that, where total density in a given area is required, overlooking transboundary distribution can underrepresent numbers by an order of magnitude. Synthesis and applications. This study provides the first comprehensive, regionally scalable distribution estimates for pinnipeds across the NWES and its constituent countries. The modelling framework is adaptable to other central-place and migratory species, supporting transboundary biodiversity assessments and international conservation policy. We discuss common limitations and misconceptions of species distribution estimates, highlight priorities for future work and underscore the need for transboundary efforts to manage wide-ranging species, providing a foundation for future ecological modelling and decision-making across shared ecosystems.
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RBINS Staff Publications 2025
