High-Resolution Habitat Mapping off Capri Island, Southern Italy

This paper deals with the characterization and mapping of benthic habitats off Capri island in the Bay of Naples, southern Italy. For this aim, we used high-resolution swath bathymetry and Side Scan Sonar imagery data integrated with grab sampling and ROV inspections. Seafloor investigations covered an area of ca 15 km2 including both the nearshore and the offshore zones up to a depth of - 140 m. The collected geophysical and sedimentological data allowed us to map benthic habitat at 1:5,000 scale on the base of both substrate and morphology. Information on benthic community resulting from grab samples analysis have been taken into account as well. Heterogeneous textural and morphological features characterize the study area. In particular, a shallow rocky (carbonate) substrate along with very scarce sediment supply favour starved conditions/amalgamation with high in situ sediment production by biological activity. Bioconstructions of different size occur as both isolated and grouped/aligned mounds surrounded by coarse organogenic deposits. The collected bathymetric data resulted in a 5x5 m DEM which permitted us to recognise meter-scale seafloor features. Based on these data, a map depicting geoform distribution in the study area was produced. Five different types of geoforms have been identified: bank, terrace, ledge, plain and slope. At the same time, a backscattering mosaic at 1m resolution from Side Scan Sonar data was used to map seafloor acoustic facies. Eleven acoustic facies have been recognized and classified on the base of ground-truth data derived from grab sampling: two of them are associated with landslide deposits, one corresponds to rocky substrate, five acoustic facies are identified by sediment grain-size and composition, two relate to bioconstruction and one is due to seafloor vegetation. Substrate features aided by benthic community data were combined with geoforms by GIS overlay analysis to obtain a map of the benthic habitats of the study area. Such a quantitative approach provided useful tools for conservation and management of marine resources with particular reference to seafloor areas that are exposed to intense human activity.