This study was aimed at identifying the food web of the red mullet, Mullus barbatus<br> in ... more This study was aimed at identifying the food web of the red mullet, Mullus barbatus<br> in order to understand how it is affected by trawling disturbance. To achieve<br> this objective: a) the main features of the red mullet habitat were investigated; b) the<br> food web of this habitat was studied in two no-trawl areas and in two areas open to<br> trawling.<br> The working hypothesis is that trawling affects the biochemistry of the sediment and<br> the trophic structure of the benthic assemblage. It was predicted: a) less biomass,<br> smaller size and higher production rate in the benthic assemblages of protected gulfs;<br> b) higher average trophic level for both the red mullet and its predators in protected<br> gulfs; c) a diet shift driven by the mechanical disturbance of trawling.<br> The results achieved confirmed our hypotheses and allowed us to characterize for<br> the first time the trophic web structure in t...
Journal of Experimental Marine Biology and Ecology, 2008
The Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent mode... more The Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent model for the study of "Lessepsian migration" and the successive colonization at new Mediterranean locations. This species in out competing indigenous bivalves is particularly well adapted to Mediterranean conditions and this is likely due to biological characteristics and physio-ecological plasticity. In the present paper, we report on clearance rate (CR), respiration rate (RR) and Scope for Growth (SFG) of B. pharaonis collected from a Western Sicilian pond (Southern Tyrrhenian, MED). Physiological variables were determined in response to a range of temperatures from 11°to 20°C and a broad range of salinities from 15 to 60 psu. Salinity and temperature had a significant influence on CR of B. pharaonis as there was a general reduction in CR with a decline in temperature from 20°C to 11°C and declining salinity from 37 to 15 psu. RR showed a general temperature dependent relationship with highest RR at 20°C. SFG showed negative values at lowest salinity of 15 psu at all tested temperatures. SFG values were generally the highest at 45 psu (at 11°C and 20°C), although SFG showed a maximum at 37 psu at 15°C. SFG values were positive over the broadest range of salinities (25 to 60 psu) at 20°C. The plasticity of the physiological rates demonstrated that B. pharaonis had the capacity to maintain positive SFG and tolerate a wide range of temperature/salinity conditions. Possible implications of high physiological plasticity of B. pharaonis in competing against indigenous bivalves are discussed.
Stable isotopes were used to examine the origin of organic matter in Icelandic Ascophyllum-based ... more Stable isotopes were used to examine the origin of organic matter in Icelandic Ascophyllum-based habitats, the role of diVerent organic matters in Wlling intertidal food webs and the food preferences of the most abundant suspension feeders, grazers and predators. We selected three intertidal sites on the SW coast of Iceland where we sampled in early September 2004, organic matter sources (POM, SOM and most abundant primary producers, A. nodosum and F. vesciculosus) and the most abundant macrofauna species (barnacles, mussels, gastropods, sponge and crabs). Even though the primary production (Ascophyllum-based) was the same at the three study sites, the isotopic composition of common-among-sites organisms varied due to local diVerences in the origin of available POM and SOM and in food web structures.
Immediate biomarker responses of two high-latitude populations of the blue mussel Mytilus edulis ... more Immediate biomarker responses of two high-latitude populations of the blue mussel Mytilus edulis to benzo[a]pyrene (B[a]P) were evaluated. Mussels collected from a clean and a polluted site in southwest Iceland were exposed to the nominal dose of 100 μg B[a]P L − l for 3 h, after 4 days of acclimatization in clean seawater. To test the sensitivity to the toxicant and immediate biological responses, the following biomarkers were used: DNA single strand breaks, heart rate and feeding rate. All the biomarkers revealed differences between the study sites. Irrespective of the origin of the organisms, the short time exposure to the high B[a]P concentration did not induce DNA single strand breaks or significantly affect the feeding rate. However, the heart rate results showed significantly different responses. The mussels from the polluted site (Reykjavík harbour) increased their heart rate when exposed to B[a]P, while no difference was observed between the heart rate values of the individuals from the clean site (Hvassahraun). The mussels seem to sense the pollutant they have been previously exposed to, and their acute response indicates physiological adaptation to the polluted environment. The results indicate limited sensitivity and temporal predictivity, i.e. transient measurable changes of these biomarkers, as well as showing that the background of the organisms should be considered when evaluating short-term biomarker responses to contaminants.
To date, the genus Marphysa is represented by only three species, Marphysa sanguinea , Marphysa a... more To date, the genus Marphysa is represented by only three species, Marphysa sanguinea , Marphysa aegypti and Marphysa birgeri in the Mediterranean Sea. Combining morphological, molecular data (16S rRNA and cytochrome c oxidase subunit I mitochondrial loci) and environmental information, we are here presenting the first Mediterranean report of Marphysa chirigota , based on the specimens collected at Rades Station (Gulf of Tunis, western Mediterranean). The current information on the distribution of of the Marphysa species strongly supports that M. sanguinea inhabits hard bottoms and has a restricted distribution close to its type location (south English coast and nearby NE European Atlantic). The specimens from Rades Station, as well as all those reported as M. sanguinea along the Tunisian coast, were found in the shallow water soft bottoms. Therefore, we suggest that the presence of M. sanguinea in Tunisia seems is doubtful, and all Marphysa species reports from Tunisia might corresp...
To date, the genus Amphiduros (Annelida: Hesionidae: Amphidurine) is considered as monotypic. Its... more To date, the genus Amphiduros (Annelida: Hesionidae: Amphidurine) is considered as monotypic. Its single species, Amphiduros fuscescens (Marenzeller, 1875), is well characterised by lacking proboscideal papillae and emerging acicular chaetae, as well as by having three antennae, eight pairs of tentacular cirri and inflated dorsal cirri with characteristic alternating length and colour (transparent, with median orange band and white tips) in live animals. Three specimens, one male and two females, were found below boulders at 5–7 m depth in Punta Santa Anna, Blanes and Cala Maset, Sant Feliu de Guixols (Catalan Sea, NW Mediterranean, Iberian Peninsula). Our finding allowed us to describe different, unreported morphological traits and lead us to support the existence of sexual dimorphism (in terms of colouring, cirri morphology and distribution of sexual products along the body). Despite A. fuscescens having been previously reported from the Atlantic and the Mediterranean (particularl...
Deep Sea Research Part I: Oceanographic Research Papers, 2019
Understanding community assembly and processes driving diversity in deep-sea environments is a ma... more Understanding community assembly and processes driving diversity in deep-sea environments is a major challenge in marine ecosystems. In this paper, we investigated the importance of environmental gradients at different spatial scales in structuring deep-sea canyon and continental slope meiobenthic nematode communities in the NW Mediterranean Sea. Three scales were investigated 1) Ecosystem: Blanes Canyon vs. adjacent open slope; 2) Water-depth within each ecosystem: 1500, 1750 and 2000 m; and 3) Vertical profile (three layers within the first 5 cm of sediment). Nematode communities were analysed in terms of density, biomass, diversity and community structure. Grain size, Chl a, Chl a: phaeopigments, CPE, organic carbon and total nitrogen were measured to assess the relationships with nematode assemblages. Blanes Canyon harbours more abundant and diverse assemblages than slope, particularly at 1,750 m and 2,000 m depth respectively. The higher canyon values may be related to the higher food availability observed in the former, which can be a consequence of the so-called "canyon effect". Slope assemblages were overall more uniform than those in the canyon, where there were greater bathymetrical differences in community structure. Densities in the canyon peaked at 1,750 m depth, which did not correspond with the bathymetric gradient in food availability. The deepest canyon station was the most similar to the slope stations in terms of both environmental conditions and nematode communities, suggesting it lied outside the canyon influence. The higher habitat heterogeneity of the canyon (indicated by its greater vertical sediment profile and water depth differences) played a key role in structuring nematode spatial distribution. Independently of the ecosystem, however, the vertical sediment profile proved to be the most determinative factor for density, community structure, and diversity.
Deep Sea Research Part I: Oceanographic Research Papers, 2017
Numerous organisms, including both passive sinkers and active migrators, are captured in sediment... more Numerous organisms, including both passive sinkers and active migrators, are captured in sediment traps together with sediments. By capturing these "swimmers", the traps become an extraordinarily tool to obtain relevant information on the biodiversity and dynamics of deep-sea organisms. Here we analyze near-bottom swimmers larger than 500 µm and their fluxes collected from eight near-bottom sediment traps installed on instrumented moorings deployed nearby Blanes Canyon (BC). Our data, obtained from November 2008 to October 2009 with a sampling rate of 15 days, constitutes the first year-long, continuous time series of the whole swimmers' community collected at different traps and bottom depths (from 300 m to 1800 m) inside a submarine canyon and its adjacent open slope (OS). The traps captured 2155 specimens belonging to 58 taxa, with Crustacea (mainly Copepoda) and Annelida Polychaeta accounting for more than 90% of the total abundance. Almost half of the identified taxa (31) were only present in BC traps, where mean annual swimmer fluxes per trap were almost one order of magnitude higher than in the OS ones. Temporal variability in swimmer fluxes was more evident in BC than in OS. Fluxes dropped in winter (in coincidence with the stormy period in the region) and remained low until the following spring. In spring, there was a switch in taxa composition, including an increase of planktonic organisms. Additionally, we report drastic effects of extreme events, such as major storms, on deep-sea fauna. The impact of such extreme events along submarine canyon systems calls to rethink the influence of climate-driven phenomena on deep-sea ecosystems and, consequently, on their living resources.
Deep Sea Research Part I: Oceanographic Research Papers, 2016
We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution... more We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution of the meiofauna in the submarine Blanes Canyon, and its adjacent western slope (NW Mediterranean margin of the Iberian Peninsula). We analyzed the relationships between the main sedimentary environmental variables (i.e. grain size, Chl-a, Chl-a:phaeopigments, CPE, organic carbon and total nitrogen) and the density and structure of the meiofaunal assemblages along a bathymetric gradient (from 500 to 2000 m depth) in spring and autumn of 2012 and 2013. Twenty-one and 16 major taxa were identified for respectively the canyon and slope, where the assemblages were always dominated by nematodes. The gradual decreasing meiofaunal densities with increasing depth at the slope showed little variability among stations and corresponded with a uniform pattern of food availability. The canyon was environmentally much more variable and sediments contained greater amounts of food resources (Chl-a and CPE) throughout, leading not only to increased meiofaunal densities compared to the slope, but also different assemblages in terms of composition and structure. This variability in the canyon is only partly explained by seasonal food inputs. The high densities found at 900 m and 1200 m depth coincided with significant increases in food availability compared to shallower and deeper stations in the canyon. Our results suggest that the disruption in expected bathymetric decrease in densities at 900-1200m water depth coincided with noticeable changes in the environmental variables typical for disturbance and deposition events (e.g., higher sand content and CPE), evoking the hypothesis of an anthropogenic effect at these depths in the canyon. The increased downward particle fluxes at 900 to 1200 m depth caused by bottom trawling along canyon flanks, as reported in previous studies, support our hypothesis and allude to a substantial anthropogenic factor influencing benthic assemblages at these depths. The possible relationships of the observed patterns and some major natural environmental (e.g., surface productivity or dense shelf water cascading) and anthropogenic (e.g. the lateral advection and downward transport of food-enriched sediments resuspended by the daily canyon-flank trawling activities) drivers are discussed.
Highlights Standing stocks were mainly driven by temporal effects such as food pulses and distu... more Highlights Standing stocks were mainly driven by temporal effects such as food pulses and disturbance events, rather than general depth patterns Topographical/hydrographical station differences are important for nematode standing stock patterns In food-rich environments such as the Blanes Canyon, nematode size distributions seem regulated by food-pulses Food pulses may induce the nematode community into a more "reproductive" state
Submarine canyons can trap and concentrate organic falls, like terrestrial debris, including wood... more Submarine canyons can trap and concentrate organic falls, like terrestrial debris, including wood. Sunken wood creates a unique ecosystem in the deep sea, which base, i.e. the microbial communities directly degrading this wood, remains poorly studied. Our aim was thus to examine the wood degrading microbial community by comparing oak 5 samples experimentally deployed in experimental mooring arrays in the Blanes Canyon (BC) and its adjacent open slope (north western Mediterranean Sea). We analyzed the microbial community by parallel tag pyrosequencing of the16S rRNA genes from wood samples recovered from different depths after 9 and 12 months of deployment. In this first study of the phylogenetic description of wood associated microbial community by 10 high throughput molecular techniques, we found that the microbial diversity was higher in samples from BC compared to the open slope. The structure of the communities were, however, not significantly different from each other, although we observed an apparent clustering according to time of immersion. Furthermore, an in depth taxonomic analysis revealed that Alphaproteobacteria was the dominant microbial taxa, with the 15 Roseobacter clade seeming to have a specialized role in the degradation of oak in BC and its adjacent slope.
Meiofaunal density distribution was studied from m to 1500 m depth inside Blanes submarine canyon... more Meiofaunal density distribution was studied from m to 1500 m depth inside Blanes submarine canyon (NW Mediterranean), and on the eastern open slope in autumn 2003 and spring 2004. Our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the Blanes Canyon that characterize it as highly heterogeneous environment. Inside the canyon area, particle fluxes were higher than on the slope area, increased from autumn to spring and mostly consisted of lithogenic material. Moreover the canyon's locations experienced more intense bottoms' currents and sediment disturbance, being reflected in a greater variability of meiobenthic densities, both between stations and sampling times than on the open slope. No clear trends (e.g. declining densities) associated with increasing depths were observed. Contrary in the open slope, current velocities were relatively lower compared with the canyon area and showed lower temporal variability. At the same time, the nutritional quality of the particle fluxes at deeper grounds were higher, probably allowing the meiofaunal densities not to change over time. In conclusion, the meiobenthos in our system apparently showed a higher temporal variability, inside the canyon area, strongly affected by particle fluxes or erosive and sediment-mixing processes linked to current modifications induced by the canyon topography.
Wood boring bivalves of the family Xylophagaidae inhabit sunken wood on the deep-sea floor where ... more Wood boring bivalves of the family Xylophagaidae inhabit sunken wood on the deep-sea floor where they play a key role in the degradation of this organic matter in the ocean. The patchiness of wood-fall habitats is impeding targeted sampling and little is therefore known on xylophagaid biology. We investigated for the first time the diversity and biogeography of Xylophagaidae in the NE-Atlantic and the Mediterranean over a broad geographic range and in various water depths using experimental wood deployments. We combined morphological and molecular analyses for species discrimination. A phylogenetic reconstruction based on 18S and 28S rRNA and COI genes revealed non-monophyly of the type genus, XylophagaTurton (1822), and led us to revise the taxonomy and erect the genus Xylonora gen. nov. COI haplotypes of the most abundant species revealed broad Atlanto-Mediterranean genetic connectivity for Xylophaga dorsalis and Xylonora atlantica new comb., while genetic connectivity appears lim...
The Gulf of Lions (GoL) is among the most productive areas of the Mediterranean Sea, with the Rhô... more The Gulf of Lions (GoL) is among the most productive areas of the Mediterranean Sea, with the Rhône River contributing with as much as 90% of the liquid and solid materials (including anthropogenic chemicals) reaching the area. In this paper, we assessed whether classical descriptive ecology and MaxEnt predictive species distribution modelling were able to provide complementary information when analysing the long-distance influence of the river discharges on the GoL benthic ecosystem. Samples were collected in August 2014 from 12 stations covering the sedimentary plain of the deep submarine delta, from the Gulf of Fos to Gruissan. Sediments were mostly muddy with a high organic carbon and low P and N contents first decreasing and then increasing from east to west. The same pattern occurred for chlorophyll-a, particulate organic carbon and sea surface temperature, and was overall correlated with metal and pollutant contents derived from agricultural, port, urban and industrial sources driven by Rhône outputs. We observed a typical deltaic succession in the benthos, showing a relatively low diversity and including polychaetes (Sternaspis scutata) and holothurians (Oestergrenia digitata) known to be indicators of high sedimentation rates. Overall, benthos showed an inversed pattern regarding environmental variables, an evident consequence of the Rhône River influence. The suitability of some species was either positively or negatively correlated with some of the environmental variables, producing species-specific predicted distribution patterns, with the highest amount of information allowing to predict distributions being mainly provided by organic pollutants. Even with a limited number of available samples, our integrated approach reveals to be a very robust tool to highlight hidden patterns and contributes to improve our knowledge on how river-mediated anthropogenic discharges may influence biodiversity distribution and functional patterns in marine benthic ecosystems.
Deep Sea Research Part II: Topical Studies in Oceanography, 2017
Abstract Blanes Canyon and its adjacent margin are important fishery areas (mainly by bottom traw... more Abstract Blanes Canyon and its adjacent margin are important fishery areas (mainly by bottom trawling) located in a highly energetic oceanographic setting in the NW Mediterranean Sea. Here we assess the spatial and temporal variability in abundance, diversity and community structure of the suprabenthic peracarid assemblages in this region and examine this variability in relation to the natural and anthropogenic (trawling fisheries) disturbance regimes. The sampling was conducted between March 2003 and May 2004 in three main fishing grounds, the canyon head (average depth: 490 m), the canyon wall (average depth: 550 m) and the eastern adjacent slope (average depth: 820 m), as well as in two non-exploited areas in the western (at 900 m depth) and eastern (at 1500 m depth) slope near the canyon mouth. A total of 138 species were identified, with amphipods being the most speciose and abundant group, followed by mysids in terms of abundance. Our results show high spatial and temporal variability in suprabenthic assemblages. Densities were higher in the canyon head and western slope, which appear to be the preferential routes for water masses and particle fluxes in months of flood events, and other energetic processes. In the canyon head, where periodic erosion processes are more active, low diversity, high dominance and higher turnover (β-diversity) were observed, apparently coupled with significant temporal fluctuations in the densities of the highly motile component of suprabenthos (mysids, predatory and scavenging amphipods). In the sedimentary more stable eastern slope, high diversity values were observed, accompanied by a higher relative contribution of the less motile groups (i.e. amphipods, most isopods, cumaceans). These groups have a closer interaction with the sediment where they exploit different food sources and are more susceptible to physical disturbance. Temporal variability in their diversity may be related to changes in food quality rather than quantity. In the canyon wall, temporal fluctuations in diversity indices were only revealed in relation to the overall higher and more continued fishing pressure observed in the canyon wall fishing ground (Cara Norte/Sot site). Here, species richness and abundance declined with increasing fishing pressure but the lowest trophic and taxonomic diversities were observed under intermediate levels of disturbance. These findings underline (i) the differences between relatively low and highly motile taxa in terms of response to disturbance events; (ii) the differences between assemblages subjected to different levels of natural disturbance and trawling pressure, which modify the common bathymetric patterns of abundance and diversity often described from continental margins.
This study was aimed at identifying the food web of the red mullet, Mullus barbatus<br> in ... more This study was aimed at identifying the food web of the red mullet, Mullus barbatus<br> in order to understand how it is affected by trawling disturbance. To achieve<br> this objective: a) the main features of the red mullet habitat were investigated; b) the<br> food web of this habitat was studied in two no-trawl areas and in two areas open to<br> trawling.<br> The working hypothesis is that trawling affects the biochemistry of the sediment and<br> the trophic structure of the benthic assemblage. It was predicted: a) less biomass,<br> smaller size and higher production rate in the benthic assemblages of protected gulfs;<br> b) higher average trophic level for both the red mullet and its predators in protected<br> gulfs; c) a diet shift driven by the mechanical disturbance of trawling.<br> The results achieved confirmed our hypotheses and allowed us to characterize for<br> the first time the trophic web structure in t...
Journal of Experimental Marine Biology and Ecology, 2008
The Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent mode... more The Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent model for the study of "Lessepsian migration" and the successive colonization at new Mediterranean locations. This species in out competing indigenous bivalves is particularly well adapted to Mediterranean conditions and this is likely due to biological characteristics and physio-ecological plasticity. In the present paper, we report on clearance rate (CR), respiration rate (RR) and Scope for Growth (SFG) of B. pharaonis collected from a Western Sicilian pond (Southern Tyrrhenian, MED). Physiological variables were determined in response to a range of temperatures from 11°to 20°C and a broad range of salinities from 15 to 60 psu. Salinity and temperature had a significant influence on CR of B. pharaonis as there was a general reduction in CR with a decline in temperature from 20°C to 11°C and declining salinity from 37 to 15 psu. RR showed a general temperature dependent relationship with highest RR at 20°C. SFG showed negative values at lowest salinity of 15 psu at all tested temperatures. SFG values were generally the highest at 45 psu (at 11°C and 20°C), although SFG showed a maximum at 37 psu at 15°C. SFG values were positive over the broadest range of salinities (25 to 60 psu) at 20°C. The plasticity of the physiological rates demonstrated that B. pharaonis had the capacity to maintain positive SFG and tolerate a wide range of temperature/salinity conditions. Possible implications of high physiological plasticity of B. pharaonis in competing against indigenous bivalves are discussed.
Stable isotopes were used to examine the origin of organic matter in Icelandic Ascophyllum-based ... more Stable isotopes were used to examine the origin of organic matter in Icelandic Ascophyllum-based habitats, the role of diVerent organic matters in Wlling intertidal food webs and the food preferences of the most abundant suspension feeders, grazers and predators. We selected three intertidal sites on the SW coast of Iceland where we sampled in early September 2004, organic matter sources (POM, SOM and most abundant primary producers, A. nodosum and F. vesciculosus) and the most abundant macrofauna species (barnacles, mussels, gastropods, sponge and crabs). Even though the primary production (Ascophyllum-based) was the same at the three study sites, the isotopic composition of common-among-sites organisms varied due to local diVerences in the origin of available POM and SOM and in food web structures.
Immediate biomarker responses of two high-latitude populations of the blue mussel Mytilus edulis ... more Immediate biomarker responses of two high-latitude populations of the blue mussel Mytilus edulis to benzo[a]pyrene (B[a]P) were evaluated. Mussels collected from a clean and a polluted site in southwest Iceland were exposed to the nominal dose of 100 μg B[a]P L − l for 3 h, after 4 days of acclimatization in clean seawater. To test the sensitivity to the toxicant and immediate biological responses, the following biomarkers were used: DNA single strand breaks, heart rate and feeding rate. All the biomarkers revealed differences between the study sites. Irrespective of the origin of the organisms, the short time exposure to the high B[a]P concentration did not induce DNA single strand breaks or significantly affect the feeding rate. However, the heart rate results showed significantly different responses. The mussels from the polluted site (Reykjavík harbour) increased their heart rate when exposed to B[a]P, while no difference was observed between the heart rate values of the individuals from the clean site (Hvassahraun). The mussels seem to sense the pollutant they have been previously exposed to, and their acute response indicates physiological adaptation to the polluted environment. The results indicate limited sensitivity and temporal predictivity, i.e. transient measurable changes of these biomarkers, as well as showing that the background of the organisms should be considered when evaluating short-term biomarker responses to contaminants.
To date, the genus Marphysa is represented by only three species, Marphysa sanguinea , Marphysa a... more To date, the genus Marphysa is represented by only three species, Marphysa sanguinea , Marphysa aegypti and Marphysa birgeri in the Mediterranean Sea. Combining morphological, molecular data (16S rRNA and cytochrome c oxidase subunit I mitochondrial loci) and environmental information, we are here presenting the first Mediterranean report of Marphysa chirigota , based on the specimens collected at Rades Station (Gulf of Tunis, western Mediterranean). The current information on the distribution of of the Marphysa species strongly supports that M. sanguinea inhabits hard bottoms and has a restricted distribution close to its type location (south English coast and nearby NE European Atlantic). The specimens from Rades Station, as well as all those reported as M. sanguinea along the Tunisian coast, were found in the shallow water soft bottoms. Therefore, we suggest that the presence of M. sanguinea in Tunisia seems is doubtful, and all Marphysa species reports from Tunisia might corresp...
To date, the genus Amphiduros (Annelida: Hesionidae: Amphidurine) is considered as monotypic. Its... more To date, the genus Amphiduros (Annelida: Hesionidae: Amphidurine) is considered as monotypic. Its single species, Amphiduros fuscescens (Marenzeller, 1875), is well characterised by lacking proboscideal papillae and emerging acicular chaetae, as well as by having three antennae, eight pairs of tentacular cirri and inflated dorsal cirri with characteristic alternating length and colour (transparent, with median orange band and white tips) in live animals. Three specimens, one male and two females, were found below boulders at 5–7 m depth in Punta Santa Anna, Blanes and Cala Maset, Sant Feliu de Guixols (Catalan Sea, NW Mediterranean, Iberian Peninsula). Our finding allowed us to describe different, unreported morphological traits and lead us to support the existence of sexual dimorphism (in terms of colouring, cirri morphology and distribution of sexual products along the body). Despite A. fuscescens having been previously reported from the Atlantic and the Mediterranean (particularl...
Deep Sea Research Part I: Oceanographic Research Papers, 2019
Understanding community assembly and processes driving diversity in deep-sea environments is a ma... more Understanding community assembly and processes driving diversity in deep-sea environments is a major challenge in marine ecosystems. In this paper, we investigated the importance of environmental gradients at different spatial scales in structuring deep-sea canyon and continental slope meiobenthic nematode communities in the NW Mediterranean Sea. Three scales were investigated 1) Ecosystem: Blanes Canyon vs. adjacent open slope; 2) Water-depth within each ecosystem: 1500, 1750 and 2000 m; and 3) Vertical profile (three layers within the first 5 cm of sediment). Nematode communities were analysed in terms of density, biomass, diversity and community structure. Grain size, Chl a, Chl a: phaeopigments, CPE, organic carbon and total nitrogen were measured to assess the relationships with nematode assemblages. Blanes Canyon harbours more abundant and diverse assemblages than slope, particularly at 1,750 m and 2,000 m depth respectively. The higher canyon values may be related to the higher food availability observed in the former, which can be a consequence of the so-called "canyon effect". Slope assemblages were overall more uniform than those in the canyon, where there were greater bathymetrical differences in community structure. Densities in the canyon peaked at 1,750 m depth, which did not correspond with the bathymetric gradient in food availability. The deepest canyon station was the most similar to the slope stations in terms of both environmental conditions and nematode communities, suggesting it lied outside the canyon influence. The higher habitat heterogeneity of the canyon (indicated by its greater vertical sediment profile and water depth differences) played a key role in structuring nematode spatial distribution. Independently of the ecosystem, however, the vertical sediment profile proved to be the most determinative factor for density, community structure, and diversity.
Deep Sea Research Part I: Oceanographic Research Papers, 2017
Numerous organisms, including both passive sinkers and active migrators, are captured in sediment... more Numerous organisms, including both passive sinkers and active migrators, are captured in sediment traps together with sediments. By capturing these "swimmers", the traps become an extraordinarily tool to obtain relevant information on the biodiversity and dynamics of deep-sea organisms. Here we analyze near-bottom swimmers larger than 500 µm and their fluxes collected from eight near-bottom sediment traps installed on instrumented moorings deployed nearby Blanes Canyon (BC). Our data, obtained from November 2008 to October 2009 with a sampling rate of 15 days, constitutes the first year-long, continuous time series of the whole swimmers' community collected at different traps and bottom depths (from 300 m to 1800 m) inside a submarine canyon and its adjacent open slope (OS). The traps captured 2155 specimens belonging to 58 taxa, with Crustacea (mainly Copepoda) and Annelida Polychaeta accounting for more than 90% of the total abundance. Almost half of the identified taxa (31) were only present in BC traps, where mean annual swimmer fluxes per trap were almost one order of magnitude higher than in the OS ones. Temporal variability in swimmer fluxes was more evident in BC than in OS. Fluxes dropped in winter (in coincidence with the stormy period in the region) and remained low until the following spring. In spring, there was a switch in taxa composition, including an increase of planktonic organisms. Additionally, we report drastic effects of extreme events, such as major storms, on deep-sea fauna. The impact of such extreme events along submarine canyon systems calls to rethink the influence of climate-driven phenomena on deep-sea ecosystems and, consequently, on their living resources.
Deep Sea Research Part I: Oceanographic Research Papers, 2016
We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution... more We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution of the meiofauna in the submarine Blanes Canyon, and its adjacent western slope (NW Mediterranean margin of the Iberian Peninsula). We analyzed the relationships between the main sedimentary environmental variables (i.e. grain size, Chl-a, Chl-a:phaeopigments, CPE, organic carbon and total nitrogen) and the density and structure of the meiofaunal assemblages along a bathymetric gradient (from 500 to 2000 m depth) in spring and autumn of 2012 and 2013. Twenty-one and 16 major taxa were identified for respectively the canyon and slope, where the assemblages were always dominated by nematodes. The gradual decreasing meiofaunal densities with increasing depth at the slope showed little variability among stations and corresponded with a uniform pattern of food availability. The canyon was environmentally much more variable and sediments contained greater amounts of food resources (Chl-a and CPE) throughout, leading not only to increased meiofaunal densities compared to the slope, but also different assemblages in terms of composition and structure. This variability in the canyon is only partly explained by seasonal food inputs. The high densities found at 900 m and 1200 m depth coincided with significant increases in food availability compared to shallower and deeper stations in the canyon. Our results suggest that the disruption in expected bathymetric decrease in densities at 900-1200m water depth coincided with noticeable changes in the environmental variables typical for disturbance and deposition events (e.g., higher sand content and CPE), evoking the hypothesis of an anthropogenic effect at these depths in the canyon. The increased downward particle fluxes at 900 to 1200 m depth caused by bottom trawling along canyon flanks, as reported in previous studies, support our hypothesis and allude to a substantial anthropogenic factor influencing benthic assemblages at these depths. The possible relationships of the observed patterns and some major natural environmental (e.g., surface productivity or dense shelf water cascading) and anthropogenic (e.g. the lateral advection and downward transport of food-enriched sediments resuspended by the daily canyon-flank trawling activities) drivers are discussed.
Highlights Standing stocks were mainly driven by temporal effects such as food pulses and distu... more Highlights Standing stocks were mainly driven by temporal effects such as food pulses and disturbance events, rather than general depth patterns Topographical/hydrographical station differences are important for nematode standing stock patterns In food-rich environments such as the Blanes Canyon, nematode size distributions seem regulated by food-pulses Food pulses may induce the nematode community into a more "reproductive" state
Submarine canyons can trap and concentrate organic falls, like terrestrial debris, including wood... more Submarine canyons can trap and concentrate organic falls, like terrestrial debris, including wood. Sunken wood creates a unique ecosystem in the deep sea, which base, i.e. the microbial communities directly degrading this wood, remains poorly studied. Our aim was thus to examine the wood degrading microbial community by comparing oak 5 samples experimentally deployed in experimental mooring arrays in the Blanes Canyon (BC) and its adjacent open slope (north western Mediterranean Sea). We analyzed the microbial community by parallel tag pyrosequencing of the16S rRNA genes from wood samples recovered from different depths after 9 and 12 months of deployment. In this first study of the phylogenetic description of wood associated microbial community by 10 high throughput molecular techniques, we found that the microbial diversity was higher in samples from BC compared to the open slope. The structure of the communities were, however, not significantly different from each other, although we observed an apparent clustering according to time of immersion. Furthermore, an in depth taxonomic analysis revealed that Alphaproteobacteria was the dominant microbial taxa, with the 15 Roseobacter clade seeming to have a specialized role in the degradation of oak in BC and its adjacent slope.
Meiofaunal density distribution was studied from m to 1500 m depth inside Blanes submarine canyon... more Meiofaunal density distribution was studied from m to 1500 m depth inside Blanes submarine canyon (NW Mediterranean), and on the eastern open slope in autumn 2003 and spring 2004. Our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the Blanes Canyon that characterize it as highly heterogeneous environment. Inside the canyon area, particle fluxes were higher than on the slope area, increased from autumn to spring and mostly consisted of lithogenic material. Moreover the canyon's locations experienced more intense bottoms' currents and sediment disturbance, being reflected in a greater variability of meiobenthic densities, both between stations and sampling times than on the open slope. No clear trends (e.g. declining densities) associated with increasing depths were observed. Contrary in the open slope, current velocities were relatively lower compared with the canyon area and showed lower temporal variability. At the same time, the nutritional quality of the particle fluxes at deeper grounds were higher, probably allowing the meiofaunal densities not to change over time. In conclusion, the meiobenthos in our system apparently showed a higher temporal variability, inside the canyon area, strongly affected by particle fluxes or erosive and sediment-mixing processes linked to current modifications induced by the canyon topography.
Wood boring bivalves of the family Xylophagaidae inhabit sunken wood on the deep-sea floor where ... more Wood boring bivalves of the family Xylophagaidae inhabit sunken wood on the deep-sea floor where they play a key role in the degradation of this organic matter in the ocean. The patchiness of wood-fall habitats is impeding targeted sampling and little is therefore known on xylophagaid biology. We investigated for the first time the diversity and biogeography of Xylophagaidae in the NE-Atlantic and the Mediterranean over a broad geographic range and in various water depths using experimental wood deployments. We combined morphological and molecular analyses for species discrimination. A phylogenetic reconstruction based on 18S and 28S rRNA and COI genes revealed non-monophyly of the type genus, XylophagaTurton (1822), and led us to revise the taxonomy and erect the genus Xylonora gen. nov. COI haplotypes of the most abundant species revealed broad Atlanto-Mediterranean genetic connectivity for Xylophaga dorsalis and Xylonora atlantica new comb., while genetic connectivity appears lim...
The Gulf of Lions (GoL) is among the most productive areas of the Mediterranean Sea, with the Rhô... more The Gulf of Lions (GoL) is among the most productive areas of the Mediterranean Sea, with the Rhône River contributing with as much as 90% of the liquid and solid materials (including anthropogenic chemicals) reaching the area. In this paper, we assessed whether classical descriptive ecology and MaxEnt predictive species distribution modelling were able to provide complementary information when analysing the long-distance influence of the river discharges on the GoL benthic ecosystem. Samples were collected in August 2014 from 12 stations covering the sedimentary plain of the deep submarine delta, from the Gulf of Fos to Gruissan. Sediments were mostly muddy with a high organic carbon and low P and N contents first decreasing and then increasing from east to west. The same pattern occurred for chlorophyll-a, particulate organic carbon and sea surface temperature, and was overall correlated with metal and pollutant contents derived from agricultural, port, urban and industrial sources driven by Rhône outputs. We observed a typical deltaic succession in the benthos, showing a relatively low diversity and including polychaetes (Sternaspis scutata) and holothurians (Oestergrenia digitata) known to be indicators of high sedimentation rates. Overall, benthos showed an inversed pattern regarding environmental variables, an evident consequence of the Rhône River influence. The suitability of some species was either positively or negatively correlated with some of the environmental variables, producing species-specific predicted distribution patterns, with the highest amount of information allowing to predict distributions being mainly provided by organic pollutants. Even with a limited number of available samples, our integrated approach reveals to be a very robust tool to highlight hidden patterns and contributes to improve our knowledge on how river-mediated anthropogenic discharges may influence biodiversity distribution and functional patterns in marine benthic ecosystems.
Deep Sea Research Part II: Topical Studies in Oceanography, 2017
Abstract Blanes Canyon and its adjacent margin are important fishery areas (mainly by bottom traw... more Abstract Blanes Canyon and its adjacent margin are important fishery areas (mainly by bottom trawling) located in a highly energetic oceanographic setting in the NW Mediterranean Sea. Here we assess the spatial and temporal variability in abundance, diversity and community structure of the suprabenthic peracarid assemblages in this region and examine this variability in relation to the natural and anthropogenic (trawling fisheries) disturbance regimes. The sampling was conducted between March 2003 and May 2004 in three main fishing grounds, the canyon head (average depth: 490 m), the canyon wall (average depth: 550 m) and the eastern adjacent slope (average depth: 820 m), as well as in two non-exploited areas in the western (at 900 m depth) and eastern (at 1500 m depth) slope near the canyon mouth. A total of 138 species were identified, with amphipods being the most speciose and abundant group, followed by mysids in terms of abundance. Our results show high spatial and temporal variability in suprabenthic assemblages. Densities were higher in the canyon head and western slope, which appear to be the preferential routes for water masses and particle fluxes in months of flood events, and other energetic processes. In the canyon head, where periodic erosion processes are more active, low diversity, high dominance and higher turnover (β-diversity) were observed, apparently coupled with significant temporal fluctuations in the densities of the highly motile component of suprabenthos (mysids, predatory and scavenging amphipods). In the sedimentary more stable eastern slope, high diversity values were observed, accompanied by a higher relative contribution of the less motile groups (i.e. amphipods, most isopods, cumaceans). These groups have a closer interaction with the sediment where they exploit different food sources and are more susceptible to physical disturbance. Temporal variability in their diversity may be related to changes in food quality rather than quantity. In the canyon wall, temporal fluctuations in diversity indices were only revealed in relation to the overall higher and more continued fishing pressure observed in the canyon wall fishing ground (Cara Norte/Sot site). Here, species richness and abundance declined with increasing fishing pressure but the lowest trophic and taxonomic diversities were observed under intermediate levels of disturbance. These findings underline (i) the differences between relatively low and highly motile taxa in terms of response to disturbance events; (ii) the differences between assemblages subjected to different levels of natural disturbance and trawling pressure, which modify the common bathymetric patterns of abundance and diversity often described from continental margins.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
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