Mapping the habitat refugia of Isidella elongata under climate change and trawling impacts to preserve Vulnerable Marine Ecosystems in the Mediterranean.

The bamboo-coral Isidella elongata is a key habitat-forming species in the deep Mediterranean Sea. This alcyonacean is listed as an indicator of Vulnerable Marine Ecosystems (VMEs) and as Critically Endangered due to bottom trawling impacts. In this work, a modeling approach was used to predict and map the habitat suitability of I. elongata in the Mediterranean Sea under current environmental conditions. Occurrence data were modeled as a function of environmental parameters. Using climate change scenarios and fishing effort data, the risk of climate change and fisheries impacts on habitat suitability were estimated, and climate refugia were identified. A drastic loss of habitat is predicted, and climate change scenarios suggest a loss of 60% of suitable habitats by 2100. In the central Mediterranean, climate refugia overlapped with active fishing grounds. This study represents the first attempt to identify hot spots for the protection of soft bottom Vulnerable Marine Ecosystems for the entire Mediterranean Sea, and highlights areas most at risk from trawling. This work is relevant to the objectives of the EU Marine Strategy Framework and Maritime Spatial Planning Directives, the Biodiversity Strategy for 2030 regarding priority areas for conservation.

Distribution of seafloor litter and its interaction with benthic organisms in deep waters of the Ligurian Sea (Northwestern Mediterranean).

The Mediterranean Sea is one of the most polluted marine basins and currently serves as a hotspot for marine litter. The seafloor represents the ultimate sink for most litter worldwide. Nevertheless, the knowledge about litter distribution and its interactions with benthic organisms in deep water is poorly understood. In 2018, we investigated spatial patterns of macro- and micro-litter distribution, and their effects on benthic communities in the Ligurian Sea. An oceanographic survey was carried out with a remotely operated vehicle and a multibeam echosounder on seven seamounts and canyons, at depths ranging from 350 to 2200 m. High litter accumulations were discovered at the mouth of the Monaco canyon, where estimated densities of up to 3.8 × 104 items km-2 were found at 2200 m depth. The highest abundance of urban litter items was found on the soft substrate, at the bottom of the deeper parts of the submarine canyons, which seem to act as conduits carrying litter from the shelf towards deeper areas. In contrast, fishing-related items were most abundant in the upper layer of the seamounts (300-600 m depths). Furthermore, more than 10% of the observed deep gorgonian colonies were entangled by lost longlines, indicating the detrimental effects of this fishing gear on benthic habitats. The discovery of new litter hotspots and the evaluation of how deep-sea species interact with litter contribute to increasing the knowledge about litter distribution and its effects on the deep ecosystem of the Mediterranean basin. All the observations recorded in this study showed substantial and irreversible changes in the deep and remote areas of marine environments, and these changes were found to be caused by humans. Our findings further stress the need for urgent and specific measures for the management of deep-sea pollution and the reduction of litter inputs in the environment.

Variability of PCB burden in 5 fish and sharks species of the French Mediterranean continental slope.

Despite being generally located far from contamination sources, deep marine ecosystems are impacted by chemicals like PCB. The PCB contamination in five fish and shark species collected in the continental slope of the Gulf of Lions (NW Mediterranean Sea) was measured, with a special focus on intra- and interspecific variability and on the driving factors. Significant differences occurred between species. Higher values were measured in Scyliorhinus canicula, Galeus melastomus and Helicolenus dactylopterus and lower values in Phycis blennoides and Lepidorhombus boscii. These differences might be explained by specific abilities to accumulate and eliminate contaminant, mostly through cytochrome P450 pathway. Interindividual variation was also high and no correlation was observed between contamination and length, age or trophic level. Despite its major importance, actual bioaccumulation of PCB in deep fish is not as documented as in other marine ecosystems, calling for a better assessment of the factors driving individual bioaccumulation mechanisms and originating high variability in PCB contamination.

Cryptic species of Archinome (Annelida: Amphinomida) from vents and seeps.

Since its description from the Galapagos Rift in the mid-1980s, Archinome rosacea has been recorded at hydrothermal vents in the Pacific, Atlantic and Indian Oceans. Only recently was a second species described from the Pacific Antarctic Ridge. We inferred the identities and evolutionary relationships of Archinome representatives sampled from across the hydrothermal vent range of the genus, which is now extended to cold methane seeps. Species delimitation using mitochondrial cytochrome c oxidase subunit I (COI) recovered up to six lineages, whereas concatenated datasets (COI, 16S, 28S and ITS1) supported only four or five of these as clades. Morphological approaches alone were inconclusive to verify the identities of species owing to the lack of discrete diagnostic characters. We recognize five Archinome species, with three that are new to science. The new species, designated based on molecular evidence alone, include: Archinome levinae n. sp., which occurs at both vents and seeps in the east Pacific, Archinome tethyana n. sp., which inhabits Atlantic vents and Archinome jasoni n. sp., also present in the Atlantic, and whose distribution extends to the Indian and southwest Pacific Oceans. Biogeographic connections between vents and seeps are highlighted, as are potential evolutionary links among populations from vent fields located in the east Pacific and Atlantic Oceans, and Atlantic and Indian Oceans; the latter presented for the first time.

Biological data extraction from imagery - How far can we go? A case study from the Mid-Atlantic Ridge.

In the past few decades, hydrothermal vent research has progressed immensely, resulting in higher-quality samples and long-term studies. With time, scientists are becoming more aware of the impacts of sampling on the faunal communities and are looking for less invasive ways to investigate the vent ecosystems. In this perspective, imagery analysis plays a very important role. With this study, we test which factors can be quantitatively and accurately assessed based on imagery, through comparison with faunal sampling. Twelve instrumented chains were deployed on the Atlantic Eiffel Tower hydrothermal edifice and the corresponding study sites were subsequently sampled. Discrete, quantitative samples were compared to the imagery recorded during the experiment. An observer-effect was tested, by comparing imagery data gathered by different scientists. Most factors based on image analyses concerning Bathymodiolus azoricus mussels were shown to be valid representations of the corresponding samples. Additional ecological assets, based exclusively on imagery, were included.

Dissolved and particulate metals (Fe, Zn, Cu, Cd, Pb) in two habitats from an active hydrothermal field on the EPR at 13 degrees N.

The distribution of Fe, Cu, Zn, Pb, Cd between the dissolved (<2 microm) and the particulate (>2 microm) fractions was measured after in-situ filtration in two hydrothermal habitats. The total metal concentration ranges exhibit a clear enrichment compared with the seawater concentration, accounting for the hydrothermal input for all the metals considered. Iron is the predominant metal (5-50 microM) followed by Zn and Cu. Cd and Pb are present at the nM level. At the scale studied, the behavior of temperature, pH and dissolved iron is semi-conservative whereas the other dissolved and particulate metals are characterized by non-conservative patterns. The metal enrichment of the >2 microm fraction results from the settlement and accumulation of particulate matter close to the organisms, acting as a secondary metal source. The enrichment observed in the dissolved fraction can be related to the dissolution or oxidation of particles (mainly polymetallic sulfide) or to the presence of small particles and large colloids not retained on the 2 microm frit. SEM observations indicate that the bulk particulate observed is characteristic of crystalline particles settling rapidly from the high temperature smoker (sphalerite, wurtzite and pyrite), amorphous structures and eroded particles formed in the external zone of the chimney. Precipitation of Zn, Cu, Cd and Pb with Fe as wurtzite, sphalerite and pyrite is the main process taking place within the area studied and is semi-quantitative. The distribution of the dominant observed fauna has been related to the gradient resulting from the dilution process, with the alvinellids worms colonizing the hotter and more variable part of the mixing zone, but also to the metallic load of the mixing zone. Dissolved and particulate metal concentrations are therefore necessary abiotic factors to be studied in a multiparametric approach to understand the faunal distribution in hydrothermal ecosystems.