Sources of anthropogenic pollution were categorised by combining elemental and isotopic techniques (C/N ratios and δ¹³C, δ¹⁵N) on samples of surficial sediments in the harbour of Naples (Southern Tyrrhenian Sea, Italy). The study area, due to the intense and diversified industrial and commercial activities, is an appropriate natural laboratory to verify reliability and relevance of geochemical methodologies applied to exploration of sources, pathways and fate of contaminants in highly polluted coastal marine systems. Application of cluster analysis to the whole dataset and resolution of a δ¹³C and δ¹⁵N Moore–Penrose system equation provided information to reliably discriminate and identify anthropogenic point sources in the studied sediments. In particular, effects of oil spilling and wastewater discharge within the area of the harbour of Naples were clearly discriminated thus suggesting high-potential of the two numerical techniques, applied to the C and N elemental and isotopic values, to explore effects of anthropogenic impact in marginal and confined coastal basins. The δ¹⁵N values showed high sensitivity to discriminate sewage discharges (treated or untreated organic matter), clearly indicating the point of emissions. The δ¹³C shows indirect capability of discriminating crude oil and petroleum products.

23 pages, 6 figures, 9 tablesFood web structure of deep-sea megafauna in the Balearic Basin (NW Mediterranean) was investigated using carbon and nitrogen stable isotopes. A total of 71 species (including 26 fish species and 19 decapod species) were analysed from samples collected with a semi-balloon otter-trawl in 2 contrasting oceanographic settings: The Catalonian Slope (CS), a continental slope area indented by several submarine canyons and an insular slope area north of Mallorca (the Balearic Slope, BS). Three faunally distinct depth zones were sampled in each area in July 2010: 450 to 600 m (upper slope), 1000 to 1300 m (middle slope) and 1400 to 2200 m (lower slope). Different physical- chemical variables and potential food sources were analysed as possible explanatory variables of trophic web variability. A δ15N- δ13C scatterplot indicated a complex food web with fish (i.e. Macrouridae and deep-sea sharks) occupying the highest trophic position. Significant differences occurred in the isotopic composition of species among upper, middle and lower slope assemblages and between the areas (CS vs. BS). Generally, higher δ15N and δ13C values were observed with increasing depth (especially among benthic feeders), and on the CS compared with the BS. Similarly, based on generalized linear models, different environmental-trophic variables ex plained the observed trends. On the BS, δ13C of species was mainly linked to physical variables and to chlorophyll a concentration at 5 m above the bottom as a proxy of marine snow, suggesting assemblages were mainly linked to vertical inputs. Conversely, on the CS, δ13C was related to trophic variables, indicating that species are linked to prey availability and less directly to primary production. The comparison suggests longer food webs over the mainland slope. © Inter-Research 2013This study was carried out within the framework of the Spanish funded project ANTROMARE (ref. CTM2009-12214-C02-01/MAR)Peer Reviewe

A number of scientific papers in the last few years singled out the influence of environmental conditions on the spatial distribution of fish species, highlighting the need for the fisheries scientific community to investigate, besides biomass estimates, also the habitat selection of commercially important fish species. The Mediterranean Sea, although generally oligotrophic, is characterized by high habitat variability and represents an ideal study area to investigate the adaptive behavior of small pelagics under different environmental conditions. In this study the habitat selection of European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus is analyzed in two areas of the Mediterranean Sea that largely differentiate in terms of environmental regimes: the Strait of Sicily and the North Aegean Sea. A number of environmental parameters were used to investigate factors influencing anchovy and sardine habitat selection. Acoustic surveys data, collected during the summer period 2002–2010, were used for this purpose. The quotient analysis was used to identify the association between high density values and environmental variables; it was applied to the entire dataset in each area in order to identify similarities or differences in the “mean” spatial behavioral pattern for each species. Principal component analysis was applied to selected environmental variables in order to identify those environmental regimes which drive each of the two ecosystems. The analysis revealed the effect of food availability along with bottom depth selection on the spatial distribution of both species. Furthermore PCA results highlighted that observed selectivity for shallower waters is mainly associated to specific environmental processes that locally increase productivity. The common trends in habitat selection of the two species, as observed in the two regions although they present marked differences in hydrodynamics, seem to be driven by the oligotrophic character of the study areas, highlighting the role of areas where the local environmental regimes meet ‘the ocean triad hypothesis’.