Papers by Emanuela Fanelli
Community structure and faunal composition of decapod crustaceans off the west coast of central I... more Community structure and faunal composition of decapod crustaceans off the west coast of central Italy (western Mediterranean) were investigated. Samples were collected during five trawl surveys carried out from June 1996 to June 2000 from 16 to 750 m depth. Multivariate analysis revealed the occurrence of five faunistic assemblages: 1) a strictly coastal community over sandy bottoms at depths <35 m; 2) a middle shelf community over sandy-muddy bottoms at depths between 50 and 100 m; 3) a slope edge community up to 200 m depth as a transition assemblage; 4) an upper slope community at depths between 200 and 450 m, and 5) a middle slope community at depths greater than 450 m. The existence of a shelfslope edge transition is a characteristic of the western and central Mediterranean where a Leptometra phalangium facies is found in many areas at depths between 120 and 180 m. The brachyuran crab Liocarcinus depurator dominates the shallow muddy-sandy bottoms of the shelf, while Parapenaeus longirostris is the most abundant species from the shelf to the upper slope assemblage. The dominant species on the middle slope are mainly nektobenthic (Aristeus antennatus, Aristaeomorpha foliacea, Plesionika martia), bentho-pelagic (Pasiphaea sivado) and benthic species (Nephrops norvegicus). The average diversity of the five assemblages defined increased with depth and the highest diversity values were found in the slope assemblages. Depth is the main factor influencing decapod assemblage composition, but sediment type and dissolved organic matter seem to be secondary structuring factors particularly in the shelf zone. RESUMEN: ASOCIACIONES DE CRUSTÁCEOS DECÁPODOS EN LA COSTA OESTE DE ITALIA CENTRAL (MEDITERRÁNEO OCCIDENTAL.
Crustaceana, 2005
The distribution of decapod crustaceans on soft substrata was studied at two sites, Montalto di C... more The distribution of decapod crustaceans on soft substrata was studied at two sites, Montalto di Castro and Gulf of Gaeta, in the central Mediterranean Sea (Tyrrhenian Sea). In the whole area, a total of 16 species of decapods (6 Natantia, Caridea; 4 Reptantia Macrura, Thalassinidea; 2 Anomura; and 4 Brachyura) were collected by a Van Veen grab. The decapod distribution seems to be influenced by granulometric composition rather than by depth. Some species demonstrated an affinity for a substratum that differs with respect to published literature records.
Marine Environmental Research, 2010
The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of M... more The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical ACI (After Control/Impact) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.
Journal of The Marine Biological Association of The United Kingdom, 2009
This study assesses the effects of bottom trawling on the feeding ecology of the scaldfish Arnogl... more This study assesses the effects of bottom trawling on the feeding ecology of the scaldfish Arnoglossus laterna, by contrasting diets in an untrawled area and in two trawled areas off northern Sicily (western Mediterranean): the Gulf of Castellammare (which hosts a 200 km 2 no-trawl area) and the gulfs of Termini Imerese and Sant'Agata. Scaldfish were collected in May -June 2005 using a commercial otter trawler between 40 and 80 m on muddy bottoms. Our data show that scaldfish is a selective feeder and consumes similar prey items in the three gulfs, although between-site differences in the relative prey abundance in the stomachs were detected. In the three gulfs scaldfish fed mainly on the crab Goneplax rhomboides and on the fish Lesueurigobius suerii, but there was an increase in the consumption of L. suerii and the shrimp Alpheus glaber in the trawled areas. Ontogenetic changes were evident in the diet of scaldfish, with juveniles preying mainly upon suprabenthic species, e.g. mysids and small decapods. While significant differences occurred in the diet of juveniles among all areas due to natural spatial variability, variations in the diet of adults, which feed on benthic prey, occurred between untrawled and trawled areas. These variations were clearly due to trawling disturbance, and no significant difference was detected in the diet of adults between the two trawled areas. On the contrary, the trophic level (d 15 N values) of scaldfish did not vary between trawled and untrawled areas and between juveniles and adults. Changes in the source of carbon, as detected by d 13 C values, were evident between juveniles and adults, evidencing a shift from a suprabenthic (juveniles) to a benthic (adults) diet.
Journal of The Marine Biological Association of The United Kingdom, 2007
Resource partitioning among early colonizing Siganus luridus and native herbivorous fish in the M... more Resource partitioning among early colonizing Siganus luridus and native herbivorous fish in the Mediterranean: an integrated study based on gut-content analysis and stable isotope signatures
Journal of Marine Systems, 2008
Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller... more Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135-780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September-November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August-September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slopeover 350 m; and the middle, deeper part of the slopeover 650-750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June
Journal of Marine Systems, 2008
Stable isotope (δ 13 C and δ 15 N) analyses were performed on suprabenthic fauna collected in the... more Stable isotope (δ 13 C and δ 15 N) analyses were performed on suprabenthic fauna collected in the western Mediterranean (NW Balearic Islands), at depths ranging between 350 and 780 m. Samples were collected seasonally at bi-monthly intervals during six cruises performed between August 2003 and June 2004, using a Macer-GIROQ suprabenthic sledge (0.5 mm mesh size). Twentyfour separate species (5 mysids, 12 amphipods, 2 cumaceans, 2 isopods, 1 euphausiid, 1 decapod and 1 fish) and bulk copepods were analyzed on a seasonal basis for stable carbon and nitrogen isotopes. Stable nitrogen isotope ratios (δ 15 N) ranged from 2.3‰ (the amphipod Lepechinella manco in September 2003) to 13.0‰ (the amphipod Rhachotropis caeca in August 2003). δ 13 C values ranged from − 24.2 (the cumacean Campylaspis sulcata in June 2004) to −16.1 (the amphipod Bruzelia typica in November 2006). Both δ 13 C and δ 15 N values suggest that there are three trophic levels within the suprabenthic community. However, considering the bathymetric range of the species, the results suggest that the deepest assemblage supported only two trophic levels. The stable isotope ratios of suprabenthic fauna displayed a continuum of values and confirmed a wide spectrum of feeding types (from filter-feeders to predators). In general, and in spite of the poor knowledge about diets available for most suprabenthic species, higher δ 15 N were found for carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods. Low overlap for δ 13 C and δ 15 N values was observed, though δ 15 N values where less variable than δ 13 C, which suggests high resource partitioning in this assemblage. Seasonal variations in isotopic composition for both δ 13 C and δ 15 N were low (less than 1‰ and 3‰, respectively) and variable depending on species. Low correlations between δ 13 C and δ 15 N of suprabenthic fauna were found for all periods studied, though increasing from February 2004 to June 2004 (after the main peak of primary production in surface). C:N ratio (indicator of lipid content) showed higher values in summer than in winter. This suggests that lipid content may explain the seasonal patterns of δ 13 C variability and, due to the increase of storage products in phytoplankton and zooplankton, it possibly indicates the peak of primary production at the surface.
Journal of Experimental Marine Biology and Ecology, 2010
The aim of the present study was to quantify the effect of formalin-ethanol preservation on the c... more The aim of the present study was to quantify the effect of formalin-ethanol preservation on the carbon and nitrogen stable isotope values of five deep-sea species (Abra longicallus, Molpadia musculus, Sipunculus norvegicus, Chirimia biceps and Nephthys hystricis). To examine temporal changes in the effects of preservation and to determine if preservation induces predictable shifts in δ 13 C and δ 15 N values, analyses were carried out after 1, 6 and 12 months of preservation. The data indicated variable effects on carbon and nitrogen isotope values among species after formalin and ethanol preservation. Formalin fixation did not affect δ 15 N values of any of the five species analysed, while it did affect δ 13 C values, with a depletion trend observed in all of the species. In general ethanol preservation did not affect nitrogen values for up to 6 months of preservation, and only the δ 15 N values of S. norvegicus became depleted after 12 months. Ethanol fixation only affected the carbon isotopic composition of M. musculus, with a progressive depletion from 1 to 12 months after preservation. Due to the different effects of preservation on stable isotope values, the use of a general and systematic correction factor was not possible. Since no effect on δ 15 N values of either formalin or ethanol fixation is evident after 6 months, we recommend that these methods be used for short-term (b 6 months) conservation and only if studies are focused on the identification of trophic levels. If changes in carbon and nitrogen isotopic values from long-preserved samples are to be used for reconstructing a food web, it is necessary to establish the effects of preservation in the whole spectrum of species evaluated.
Journal of Marine Systems, 2008
Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller... more Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135-780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September-November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August-September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slope — over 350 m; and the middle, deeper part of the slope — over 650-750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June 2004-August 2003), autumn-winter (September and November 2003, February 2004), and spring (April 2004), being especially well established off Sóller. In general, suprabenthos was significantly correlated with the sediment variables (e.g. total organic matter content (% OM), potential REDOX), whereas zooplankton was almost exclusively dependent on Chl a at the surface, which suggests two different food sources for suprabenthos and zooplankton. The increase of suprabenthos abundance in April-June was paralleled by a sharp increase ( ca. 2.8 times) in the %OM on sediment during the same period, coupled ca. 1-2 months of delay with the peak of surface Chl a recorded in February-March (from satellite imagery data). Suprabenthos biomass was also correlated with salinity close to the bottom, suggesting a link between suprabenthos abundance and changes in the oceanographic condition of water masses close to the bottom. It is suggested that a higher suprabenthos biomass recorded off Sóller in comparison to that off Cabrera in June could, in turn, be related to a seasonal inflow of Levantine Intermediate Water (LIW) in April-June in this area at mid bathyal depths (350-650 m). This trend would be based on: 1) it was evident only at mid-slope depths between 350-750 m, coinciding with the LIW distribution, and 2) it was not recorded among zooplankton (collected throughout the water column). The possible effect of the fluctuations of suprabenthos and zooplankton on higher trophic levels has been explored studying the diet and food consumption rates of the red shrimp Aristeus antennatus, as indicator species by its dominance in bathyal communities. A. antennatus increased its food consumption from February to April-June 2004 off Sóller, which in the case of large (CL > 40 mm) specimens was found in both areas. In addition, there was a shift of diet from winter to spring-early summer. In this last period, A. antennatus preyed upon euphausiids and mesopelagic decapods and fish, while benthos (e.g. polychaetes and bivalves) decreased in the diet. This indicates an increase in the food consumption and probably in the caloric content of the diet in pre-spawning females in April-June 2004, which is synchronized with the period when gonad development begins in A. antennatus females (May-June). Anyway, macrozooplankton, and not suprabenthos, is crucial as a high energetic food source in the coupling between food intake and reproduction in the red shrimp.
Deep-sea Research Part I-oceanographic Research Papers, 2011
The food-web structure of the epibenthic and infaunal invertebrates on the continental slope of t... more The food-web structure of the epibenthic and infaunal invertebrates on the continental slope of the Catalan Sea (Balearic basin, NW Mediterranean) was investigated using carbon and nitrogen stable isotopes on a total of 34 species, and HPLC pigment analyses for three key species. Samples were collected close to Barcelona (NE Iberian Peninsula), between 650 and 800 m depth and between February 2007 and February 2008. Mean d 13 C values ranged from À 21.0% (small Calocaris macandreae and Amphipholis squamata) to À 14.5% (Sipunculus norvegicus). Values of d 15 N ranged from 4.0% (A. squamata) to 12.1% (Molpadia musculus). The stable isotope ratios of benthic fauna displayed a continuum of values (e.g. d 15 N range of 8%), confirming a wide spectrum of feeding strategies (from active suspension feeders to predators) and complex food webs. According to the available information on diets of benthic fauna, the lowest values were found for surface deposit feeders (small C. macandrae and the two ophiuroids A. squamata and Amphiura chiajei) and active suspension feeders (Abra longicallus and Scalpellum scalpellum) feeding on different sizes of particulate organic matter (POM), among which small particles may exhibit lower d 15 N. High annual mean d 15 N values were found among sub-surface deposit feeders, exploiting refractory or frequently recycled organic matter that is enriched in d 15 N. Carnivorous polychaetes (Nephtys spp., Oenonidae and Polynoidae) and large decapods (Geryon longipes and Paromola cuvieri) also displayed high d 15 N values. d 13 C ranges were particularly wide among surface deposit feeders (ranging from À 21.0% to À 16.4%), suggesting exploitation of POM of both terrigenous and oceanic origins. Correlation between d 13 C and d 15 N was generally weak, indicating multiple carbon sources, likely due to the consumption of different kinds of sinking particles (e.g. marine snow, phytodetritus, etc.), sedimented and frequently recycled POM, together with macrophyte remains. The stronger d 13 C-d 15
Marine and Freshwater Research, 2010
Because trawling disturbs benthic organisms, it could affect the diet of benthic-feeding fish wit... more Because trawling disturbs benthic organisms, it could affect the diet of benthic-feeding fish with implications for food-web dynamics. The present study assessed the effects of commercial trawling on the trophodynamics and diet of pandora, Pagellus erythrinus, by comparing its stomach contents and stable-isotope (d 15 N and d 13 C) composition in two trawled and two untrawled gulfs in northern Sicily (central Mediterranean). Fish were collected on muddy bottoms at 50-100-m depth. Higher abundance and biomass and a slightly larger mean body length were found in the untrawled gulfs. The feeding habits were similar although more selective in the untrawled gulfs. The diet was mainly composed of decapod crustaceans (especially the brachyuran crab Goneplax rhomboides) and of polychaetes. The trophic level of pandora, estimated by its d 15 N values, was higher in the untrawled gulfs. No clear trend between trawled and untrawled gulfs was found for the source of carbon in the diet (d 13 C). The diet of a benthic feeder such as pandora may be used as an indirect indicator of trawling disturbance, as long as stomach contents and stable-isotope analysis are used jointly to assess the diet and trophodynamics of a species.
Journal of Sea Research, 2009
The distribution of megabenthic epifauna (invertebrates) in the Balearic Basin (western Mediterra... more The distribution of megabenthic epifauna (invertebrates) in the Balearic Basin (western Mediterranean) has been analyzed at depths between 427 and 2265 m after compiling samplings performed in 1985-1992 and 2007-2008 with an OTSB-14 bottom trawl. 84 epibenthic taxa of invertebrates (excluded decapod crustaceans) were collected. Epibenthic assemblages were organized in five groups (n-MDS analyses) as a function of increasing depth: upper slope assemblage, U, hauls between 427 and 660 m; middle slope assemblages M1 and M2, hauls between 663-876 m and 864-1412 m, respectively; lower slope assemblages L1 and L2, hauls between 1488-1789 m and 1798-2265 m, respectively). We found significant differences in assemblage composition between all depth-adjacent pairs of groups. Trends in the distribution of biomass vs. depth and within assemblages varied when hauls taken over insular were compared to those over mainland slopes. Over insular slopes we found (n-MDS) only four distinct depth assemblages, with significant differences between all depth-adjacent group pairs, except between L1 and L2. Over the mainland slope, two peaks of biomass situated at U (427-660 m) and at L1 (1488-1789 m) were clearly identified, attributable to the echinoid Brissopsis lyrifera and holothurian Molpadia musculus at U and to the synallactid holothurian Mesothuria intestinalis at L1. The distribution of biomass vs. depth on insular slopes did not follow this pattern, showing no significant biomass peak below 1000 m and a total biomass an order of magnitude lower than adjacent to the mainland. After compiling available environmental data over the mainland slope off Barcelona, we found coincidence between the peak biomass of Mesothuria intestinalis and: i) a significant increase of labile OM (%OrgC, C/N, hydrolizable aminoacids-EHAA, and the EHAA/THAA-total hydrolizable aminoacids-ratio) over 1600 m; and ii) an increase of turbidity and T at 1500-1600 m in February 2008. We suggest that such OM inputs must likely be associated to the formation of nepheloid layers close to submarine canyons, probably associated with oceanographic processes in deep water masses in the area. This would explain why aggregations of M. intestinalis were linked to the mainland part of the Balearic basin, with highest densities located south of canyons. If hotspots of biomass as cited here for M. intestinalis are regulated by factors such as river inputs, both natural climatic changes (e.g. changes in rainfall regimes) and human impact (e.g. river damming) may affect deep-Mediterranean communities below 1000 m.
Estuarine Coastal and Shelf Science, 2011
Keywords: suprabenthos spatial variability assemblage structure diversity stable isotopes trawl-b... more Keywords: suprabenthos spatial variability assemblage structure diversity stable isotopes trawl-ban a b s t r a c t Meso-scale spatial variability of coastal suprabenthic communities inhabiting muddy bottoms at 50e80 m depth in three gulfs of northern Sicily (Western Mediterranean) was here investigated. Although similar as concerns the hydrological and oceanographic conditions, the three areas, that encompass a large portion of the continental shelf (135 km), are characterized by different geo-morphological features. In addition, they are subjected to different trawl fishery pressures. The Gulf of Castellammare is a semi-enclosed bay, where the trawling activity has been banned since 1990. The Gulf of Termini Imerese and the Gulf of Sant'Agata are open areas, subjected to high trawl fishing intensity. In terms of density, gammarid amphipods showed differences among the three gulfs; in terms of biomass, cumaceans and amphipods were more abundant in the Gulf of Castellammare than in the other two areas. Multivariate analyses provided evidence for separation of suprabenthic assemblages between the Gulf of Castellammare and the other two gulfs. The Gulf of Castellammare seemed to host the most diversified and stable community according to aand b-diversity indices. In the same way the low value of d 13 C vs. d 15 N correlation found in the gulf of Castellammare, which evidences the occurrence of several food sources, supports the idea of a higher stability in the semi-enclosed, trawl-ban area. In the other two areas d 13 C vs. d 15 N correlations were high, suggesting the existence of a pelagic source sustaining the suprabenthic communities. This is also confirmed by the lower d 13 C concentrations found in suprabenthic species. Taking into account the homogeneous oceanographic conditions among gulfs, other factors, such as geo-morphology and trawling pressure should be involved in the observed differences among the three areas in terms of assemblage structure, diversity, and trophodynamics of suprabenthic communities.
Journal of Sea Research, 2011
The composition of suprabenthic crustacean assemblages, their diversity, production (P) and produ... more The composition of suprabenthic crustacean assemblages, their diversity, production (P) and production/ biomass (P/B) ratios, were analyzed at species level along two transects situated to the north (N) and south (S) of Mallorca (Balearic Islands, western Mediterranean) at depths between 134 m and 760 m, based on a ca. bi-monthly sampling performed between August 2003 and June 2004. Differences with depth and season in assemblage composition and diversity were analyzed as a function of the contrasting environmental features (e.g. water mass dynamics) of the two areas. We identified 187 species (18 decapods, 5 euphausiids, 16 mysids, 76 gammaridean amphipods, 13 hyperiids, 1 caprellid, 21 isopods and 37 cumaceans). Substantial mesoscale variability in the deep-sea suprabenthic assemblages coupled with diversity trends between the N and S transects were found. Seasonality was the most important gradient influencing the dynamics of suprabenthos over the upper (350 m) and middle (650-750 m) slope in the N area. Conversely, the S area appeared to be more stable temporally with depth as the main gradient inducing assemblage differences. Different depth-related patterns were observed both for diversity and P/B. To the north diversity was very low at the shelf-break, increasing on the upper-slope (H′ N 3.00) and then decreasing again on the middle-slope. To the south diversity increased smoothly downward, reaching the highest values on the middle-slope. Regarding productivity, P/B was highest at intermediate depths to the north (over ca. 450-500 m), while to the south highest P/Bs were found deeper (over ca. 600-650 m). The higher P/B at intermediate depths found along N are likely due to higher % of organic matter (OM) in sediments, a product of oceanographic frontal systems. In particular, P/B was higher along N among omnivores and detritus feeders (e.g. Andaniexis mimonectes, Lepechinella manco and combined cumaceans), coupled to enriched OM in sediments, while along S mesoplanktonic carnivores (Rhachotropis spp.) had higher P/Bs. We conclude that on the north slope the influence of frontal systems and more active flow dynamics of different water masses (WIW and LIW) increases natural disturbance in the area, increasing productivity and diversity of suprabenthic peracarids in the Benthic Boundary Layer. Also, species showed a displacement of their average distributions (their Centres of Gravity, CoG) to shallower depths along N, which is another indicator of more favorable habitat conditions for suprabenthos in the 400-500 m range at N.
Journal of Sea Research, 2009
The trophodynamics of suprabenthic fauna were analyzed in the Gulf of Castellammare (North-wester... more The trophodynamics of suprabenthic fauna were analyzed in the Gulf of Castellammare (North-western Sicily, Italy) at depths ranging between 40 and 80 m. Variations in species abundance and biomass together with changes in nitrogen and carbon stable isotope ...
Journal of Sea Research, 2010
The spatial and temporal changes of near-bottom macrofauna (suprabenthos and macroplankton) and t... more The spatial and temporal changes of near-bottom macrofauna (suprabenthos and macroplankton) and the trophic relationships of megabenthic decapod crustaceans were analyzed off the Catalonian coasts (western Mediterranean) around Berenguera ...
Deep-sea Research Part I-oceanographic Research Papers, 2011
A seasonal analysis of deep-sea infauna (macrobenthos) based on quantitative sampling was conduct... more A seasonal analysis of deep-sea infauna (macrobenthos) based on quantitative sampling was conducted over the Catalan Sea slope, within the Bes os canyon (at $ 550-600 m) and on its adjacent slope (at 800 m). Both sites were sampled in February, April, June-July and October 2007. Environmental variables influencing faunal distribution were also recorded in the sediment and sediment/water interface. Dynamics of macrobenthos at the two stations showed differences in biomass/abundance patterns and trophic structures. Biomass was higher inside the Bes os canyon than on the adjacent slope. The community was mostly dominated by surface-deposit feeding polychaetes (Ampharetidae, Paraonidae, Flabelligeridae) and crustaceans (amphipods such as Carangoliopsis spinulosa and Harpinia spp.) inside the canyon, while subsurface deposit feeders (mainly the sipunculan Onchnesoma steenstrupii) were dominant over the adjacent slope. The taxonomic composition in the suprabenthic assemblages of polychaetes, collected on the adjacent slope by a suprabenthic sledge, was clearly different from that collected by the box-corer. The suprabenthic assemblage was dominated by carnivorous forms (mainly Harmothoe sp. and Nephthys spp.) and linked to higher near-bottom turbidity. Inside Bes os a clear temporal succession of species was related to both food availability and quality and the proliferation of opportunistic species was consistent with higher variability in food sources (TOC, C/N, d 13 C) in comparison to adjacent slope. This was likely caused by a greater influence of terrigenous inputs from river discharges. Inside the canyon, Capitellidae, Spionidae and Flabelligeridae, in general considered as deposit feeders, were more abundant in June-July coinciding with a clear signal of terrigenous carbon (depleted d 13 C, high C/N) in the sediments. By contrast, during October and under conditions of high water turbidity and increases of TOM, carnivorous polychaetes (Glyceridae, Onuphidae) increased. Total macrobenthos biomass found over Catalonian slopes were higher than that found in the neighboring Toulon canyon, probably because the two canyons are influenced by different river inputs, connected with distinct terrigenous sources.
Deep-sea Research Part I-oceanographic Research Papers, 2009
Deep-sea Research Part I-oceanographic Research Papers, 2010
We analyzed the distribution, diversity, and composition of western Mediterranean macroplankton (... more We analyzed the distribution, diversity, and composition of western Mediterranean macroplankton (excluding gelatinous taxa) in the water column over depths of ca. 550-850 m, with special attention to near-bottom (0-1.5 and ca. 5-77 m above the bottom, mab) levels, and including data from three areas (off the coasts of Catalonia, and to the NW, and SE of Mallorca, Balearic Islands) in the period 1991-2008. Spatio-temporal changes in macroplankton abundance were evaluated as follows: (i) by seasonal sampling in 2007 off the Catalonian coast, (ii) by comparing Catalonian and Balearic Island slopes, and (iii) by comparing a fixed station on the Catalonian slope (at 550-800 m depth) at decadal time scales. Diversity (in terms of species richness, S) was greater (i) at ca. 5-77 mab than at 0-1.5 mab, (ii) over the insular slopes of the Balearic Island (around Mallorca) than over the mainland Catalonian slopes, and (iii) in the period 1991/1992 than in 2007, likely related to higher values of the North Atlantic Oscillation (NAO) index in 1991/1992. In most analyses species composition was strongly influenced by the degree of stratification and homogenization of the water column in summer-autumn and winter-spring respectively and by location (longitude). Changes consisted mainly of higher density of macroplankton (e.g. abundance of the dominant euphausiids Nematoscelis megalops, Meganyctiphanes norvegica and Euphausia krohni and of the fish Cyclothone braueri) between June and October, parallel to an increase in the T and S close to the bottom. This coincided with changes in the flow of Levantine intermediate water (LIW) in the area. Aggregation of adult forms of the dominant species close to the bottom in summer-autumn could be favored because summer is the period of highest density of food -copepods, mainly Calanus helgolandicus -near the bottom off the Catalan slope. The formation of a thermocline in the water column and the reinforcement of the permanent thermohaline front at the shelf-slope break during summer at ca. 400 m in the Balearic Basin may also enhance this tendency toward greater aggregation of deep macroplankton under stratified water column conditions.
Journal of Marine Systems, 2011
Food web structure of the macroplankton/micronekton fauna on the continental slope of the Catalan... more Food web structure of the macroplankton/micronekton fauna on the continental slope of the Catalan Sea (Balearic basin, NW Mediterranean) was investigated using carbon and nitrogen stable isotope tracers on a total of 34 taxa. Samples were collected close to Barcelona, Spain, on the middle slope, at a seasonal scale. Mean δ 13 C values ranged from − 22.1‰ (Salpa maxima) to − 16.9‰ (the mysid Eucopia hanseni). Values of δ 15 N ranged from 2.5‰ (the hyperiid Vibilia armata) to 9.8‰ (the pelagic polychaete Tomopteris sp.). The stable isotope ratios of this fauna displayed a continuum of values over the δ 15 N range of 7‰, confirming a wide spectrum of feeding strategies (from filter feeders to predators). High annual mean δ 15 N values were found among carnivorous large zooplankton and micronekton, including species that prey on gelatinous plankton (i.e. salps, siphonophores), euphausiids, natantian decapod crustaceans and fish (i.e. myctophids and stomiiformes). In agreement with the available information on diets of planktonic taxa, the lowest isotope ratios were found for filter feeders (V. armata, S. maxima, the pteropods Cymbulia peroni and Cavolinia inflexa, ostracods and the thaliacean Pyrosoma atlanticum), all of which feed on particulate organic matter. We found three trophic levels in macroplankton/micronekton food webs based on a 15 N-enrichment factor of~2.5‰ per level. The range of δ 13 C was particularly wide among carnivores (− 20.7‰ to − 16.6‰), suggesting predation on a variety of prey from gelatinous zooplankton (which displayed more depleted δ 13 C signatures) to small fishes and decapods. Correlation between δ 13 C-δ 15 N was generally weak, likely due to the consumption of different kinds of sinking particles (e.g. marine snow, phytodetritus), some constituted of multiply recycled particulate organic matter (POM). However, higher δ 13 C-δ 15 N correlations were observed during winter and spring, periods of water column homogenization, suggesting that the planktonic community assimilates pulses of new production from the photic zone (peaking in January-February). Low correlations were observed during periods of water column stratification, particularly in summer, when production is especially low, suggesting that in this period macroplankton-micronekton community rely on sources other than surface primary production such as POM derived from river discharge.
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Papers by Emanuela Fanelli