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Sources of anthropogenic pollution were categorised by combining elemental and isotopic techniques (C/N ratios and δ(13)C, δ(15)N) 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 δ(13)C and δ(15)N 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 δ(15)N values showed high sensitivity to discriminate sewage discharges (treated or untreated organic matter), clearly indicating the point of emissions. The δ(13)C shows indirect capability of discriminating crude oil and petroleum products.

The trophodynamics of mesopelagic (macrozooplankton/micronekton) and Benthic Boundary Layer (suprabenthos = hyperbenthos) faunas from the Algerian basin were characterized on a seasonal scale through stable carbon and nitrogen isotopic analyses of a total of 34 species and two broad taxa (Copepoda and Cumacea). This is the first study simultaneously focused on trophodynamics of deep-sea zooplankton and suprabenthos. Samples were collected southeast of Mallorca (Algerian Basin, Western Mediterranean), on the continental slope close to Cabrera Archipelago, at 650-780 m depths, ca. bi-monthly between August 2003 and June 2004. Mean δ 13 C values of suprabenthos ranged from -21.1‰ (Munnopsurus atlanticus) to -16.7‰ (Cyclaspis longicaudata). Values of δ 15 N ranged from 2.8‰ (Lepechinella manco) to 9.9‰ (larvae of Gnathia sp.). The stable isotope ratios of suprabenthic fauna displayed a continuum of values, confirming a wide spectrum of feeding guilds (from filter feeders/surface deposit feeders to predators). According to the available information on diets for suprabenthic species, the highest annual mean δ 15 N values were found for the hematophagous isopod Gnathia sp. parasite on fish (represented by Praniza larvae) and carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods, and the lowest δ 15 N values were found for two cumaceans (Cyclaspis longicaudata and Platysympus typicus) feeding on detritus. Assuming a 15 N-enrichment factor of 2.5‰ and deposit feeders as baseline we found three trophic levels in suprabenthic food webs. δ 13 C ranges were particularly wide among deposit feeders (ranging from -21.8 to -17.3‰) and omnivores (from -20.5 to -18.8‰), suggesting exploitation of particulate organic matter (POM) of different characteristics. Our isotopic analyses revealed lower ranges of δ 13 C and δ 15 N for macrozooplankton/micronekton, compared with suprabenthos. δ 13 C values of zooplankton taxa ranged from -21.1‰ (the hyperiid Phrosina semilunata) to -19.9‰ (the decapod Pasiphaea multidentata), while δ 15 N values ranged from 3.9‰ (P. semilunata) to 7.5‰ (P. multidentata). Among zooplankton, more enriched δ 15 N values were found among carnivores (e.g. the fish Cyclothone spp. and Pasiphaea multidentata) preying on copepods, hyperiids, euphausiids and small fish. The lowest δ 15 N values were found for hyperiids 3 that feed on the mucus nets of salps (e.g. Vibilia armata). After contrasting isotope analysis with dietary data, we conclude there were two trophic levels among zooplankton/micronekton. Strong correlation between the mean annual δ 15 N and δ 13 C values was found for zooplankton (R 2 =0.7), but not for suprabenthos, which suggests a single source of carbon for plankton. We found a general seasonal trend for δ 13 C enrichment from late autumn (November) to late winter-spring (February-April) for both suprabenthos and zooplankton. The δ 13 C enrichment in February-April was correlated in zooplankton with higher surface chlorophyll a concentration one month before sampling. ...

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’.