Deep Mediterranean Sea Research Articles

Deep Mediterranean turbulent convection

Life in the deep sea requires turbulent mixing and advective transporting water flows for the supply of nutrients. However, because of the harsh environmental constraints in the deep sea, detailed quantitative measurements are scarce. Recent high-resolution measurements demonstrate that the deep Mediterranean Sea waters are far from stagnant, even though temperature variations over a day and 100 m in depth are of the order of 0.0001°C. An innovative 3D-mooring structure was used supporting 550 highly sensitive temperature sensors.

Towards an Ecosystem-Based Marine Spatial Planning in the deep Mediterranean Sea.

The deep sea covers about 79% of the Mediterranean basin, including habitats potentially able to deliver multiple ecosystem services and numerous resources of high economic value. Thus, the deep Mediterranean Sea represents an important frontier for marine resources exploitation, which is embedded within the European Blue Growth Strategy goals and agendas. The deep sea is crucial for the ecological functioning of the entire basin. For this reason, the deep Mediterranean deserves protection from the potential cumulative impacts derived from existent and developing human activities. Marine Spatial Planning (MSP) has been identified as key instrument for spatially allocating maritime uses in the sea space avoiding spatial conflicts between activities, and between activities and the environment. Indeed, MSP incorporates the ecosystem-based approach (EB-MSP) to balance both socio-economic and environmental objectives, in line with the Maritime Spatial Planning Directive and the Marine Strategy Framework Directive. Despite MSP is under implementation in Europe, the Directive is not applied yet for the managing and monitoring of the environmental status of the deep sea. In the Mediterranean, deep areas fall both in internal and territorial waters, and in High Seas, and its management framework turns out to be complicated. Moreover, a certain level of cumulative impacts in the deep Mediterranean has been already identified and likely underestimated because of paucity of knowledge related with deep-sea ecosystems. Thus, the implementation of scientific knowledge and the establishment of a sustainable management regime of deep-sea resources and space are urgent. This study aims at reflecting on the best available ecological knowledge on the deep Mediterranean to incorporate conservation objectives in EB-MSP. We propose a framework to include key ecological principles in the relevant phases of any EB-MSP processes taking in consideration existing socio-economic and conservation scenarios in the region. We add the uncertainty principle to reflect on the still unexplored and missing knowledge related to the deep Mediterranean. Here, we resume some guidelines to overcome limits and bottlenecks while ensuring protection of deep-sea ecosystems and resources in the Mediterranean Sea.

Towards a marine strategy for the deep Mediterranean Sea: Analysis of current ecological status

The Marine Strategy Framework Directive (MSFD), introduced in June 2008, was adopted to achieve a Good Environmental Status (GES) in the EU's marine waters and to protect resources of socio-economic interest. The MSFD exerts to the marine area over which a Member State exercises jurisdictional rights in accordance with the United Nations Convention on the Law of the Sea (UNCLOS), including the deep-sea waters, seafloor and sub-seafloor of the Exclusive Economic Zones (EEZ). However, currently the MSFD focuses on coastal habitats and the shallow-water seafloor to the detriment of the deeper habitats. Despite the huge dimension of the deep sea (below 200 m of depth) covering more than 65% of the Earth's surface and including >95% of the global biosphere, the relevance of the dark portion of the seas and oceans is still almost completely neglected. Given the important bi-directional links between shallow and deep ecosystems, there is a clear need for extending the implementation of the MSFD into the deep sea, to define a sound ecosystem-based approach for the management and protection of deep-sea ecosystems and attain GES. We assembled data on drivers, anthropogenic pressures and impacts concerning the MSFD descriptors pertaining to the Mediterranean deep sea. We list deep-sea monitoring activities and the main sources providing benchmark conditions, and discuss knowledge and geographic coverage gaps. MSFD descriptors apply to the deep sea as to coastal waters, and ought to be monitored contemporaneously. We provide recommendations for guidelines for future deep-sea monitoring in the Mediterranean Sea.

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Seasonality combined with the orientation of surfaces influences the microbial community structure of biofilms in the deep Mediterranean Sea

Attachment to surfaces represents an important life strategy for microbial communities as indicated by the rapid colonization of biotic and abiotic surfaces in marine waters. However, little attention has been paid to the development of biofilm-associated microbial communities and the environmental parameters influencing biofilm development in the deep sea. In this study, a deep-sea experimental setup was used to follow the development of the microbial community colonizing solid surfaces deployed at 4500 m depth at the deepest point of the Mediterranean Sea. The experiment was performed during summer (May to October 2007) and winter (October 2007–May 2008), each lasting for 155 d. The phylogenetic composition of the biofilm community was determined by tag sequencing of the 16S rRNA gene. We investigated whether the composition of the deep-sea microbial biofilms is influenced by seasonality. Based on tag sequencing, operational taxonomic units were identified and diversity indices calculated. Seasonality combined with the orientation of the solid surface on which the biofilms were growing was the main factor influencing the structure of the microbial community. The most abundant phyla of deep-sea biofilm communities attached to the solid surfaces were Gammaproteobacteria (range: 10.8%–92.6%), Alphaproteobacteria (range: 34.9%–92.6%) and Betaproteobacteria (range: 0.3%–2.1%), irrespective of the variables (surface, orientation, season). Flavobacteria and Epsilonbacteria show a clear preference with respect to the orientation of the deployed surfaces during the winter, however, they were essentially absent at the surfaces during the summer. Some bacterial classes such as Campylobacterales and Rhodobacterales showed distinct preferences for specific seasons or orientation of the substrate. Taken together, we conclude that even on deep-sea biofilms, there is to some extent seasonality detectable in the composition of the surface associated prokaryotic community, despite the fact that the deep-sea is, in terms of physico-chemical parameters, a fairly stable environment.

Meiofaunal distribution in the Levantine Basin (Eastern Mediterranean): Spatial variability at different scales, depths and distance-to-coast

Deep-sea ecosystems have been characterised in many ways, such as deserts, stable, monotonous, poor, remote. Building on knowledge over the years, we now know that these extreme environments are highly variable and diverse hosting rich benthic communities that are largely affected and structured by food availability and quality. In the land-locked, oligotrophic Mediterranean Sea, food supply to the deep sea is expected to be dependent on pelagic production but also to be affected by inputs from the surrounding landmasses. Having this in mind, we used samples collected during the LEVAR expedition on board R/V METEOR (M71/2, winter 2006–2007) from two distinct deep-sea areas in the Levantine Sea for describing meiobenthic communities in relation to factors that may drive their spatial distribution, variability and patchiness at several scales. Area 1 (within the Pliny Trench) is located close to the island of Crete at ca 4000 m depth, whereas Area 2 (within Herodotus Abyssal Plain) is more distant from the island but shallower (ca 2700 m). Independent multiple-corer deployments performed at three stations within each area, the use of several sediment cores from each deployment, and the vertical sectioning of one sediment sample per deployment, allowed to explore meiobenthic patterns at multiple scales. A set of permutational analyses indicated differences between the two areas in terms of sedimentary food proxies that were coupled with corresponding differences in meiofauna richness, composition, and in abundances of the two most dominant meiobenthic metazoans, i.e. nematodes and copepods. Though to a lesser extent, variability in meiobenthic characteristics was also detected within and among stations. A similar trend was not clearly evident within deployments. Changes in meiofauna distribution occurred in relation to sediment depth layer as well, with evidence that the meiofauna vertical profile may differ between the two areas. Overall, our study shows that higher meiobenthic variability in the eastern Mediterranean deep sea is accounted for at the scale of area/habitat. Inferences of our results in light of previous findings in the same area imply that the relationship between food and meiobenthic composition could not be attributed to bathymetry or distance from the land, but is more probably explained by the high complexity and dynamics of trench habitats and their role as depositional environments acting as physical traps of organic material.

Radiocarbon measurements of foraminifera with the mini carbon dating system (MICADAS) at the Centro Nacional de Aceleradores

Radiocarbon (14C) measurements of foraminifera are often challenging as their reliability and accuracy can be biased by several complicating factors. In this work, at the Centro Nacional de Aceleradores (CNA) in Seville, an automated setup with a Carbonate Handling System coupled with an automated graphitization system has been tested to investigate the potential for running samples of foraminiferal carbonate for AMS 14C dating of marine archives. The reproducibility of 14C ages for blanks and standard materials indicates that reliable 14C analyses are possible for carbonate samples with a 14C age up to 50,000 yr BP. With this automated procedure we were able to date monospecific planktonic foraminifera younger than 1000 yr BP. Biological mixing and high sedimentation are potentially complicating mechanisms resulting in anomalous young 14C ages in planktonic foraminifera from the deep Mediterranean Sea.

Aethozooides uraniae, a new deep-sea genus and species of solitary bryozoan from the Mediterranean Sea, with a revision of the Aethozoidae

Bryozoa is a phylum of about 6000 extant species that are almost exclusively colonial. Few species of the uncalcified Gymnolaemata, the ctenostomes, however, show solitary forms that essentially consist of single zooids. Recently, several specimens of a solitary ctenostome bryozoan were encountered for the first time in the deep Mediterranean Sea, at the edge of an anoxic brine lake. Differences in size, tentacle number, and in the variability of cystid appendages set these specimens apart from all other known solitary species. Moreover, additional morphological autapomorphic traits suggest the erection of a novel genus to allocate the new species. Consequently, the new taxon Aethozooides gen. nov. is proposed in virtue of the general resemblance of the Mediterranean specimens with those of the genus Aethozoon Hayward, 1978. Aethozooides uraniae gen. et sp. nov. shows significant variability in the number and location of cystid appendages that range from two on the basal side to one or two on the zooid mid-peristomial position and/or, rarely, on the terminal frontal side. The polypide possesses a distinct, long tentacle crown always carrying 10 tentacles. The prominent retractor muscle consists of numerous bundles that, in contrast to other known gymnolaemates, attach not only to the lophophoral base but also to various parts of the gut. Distally, the aperture shows a set of four apertural muscles including four parieto-vaginal bands. Reviewing the state and diversity of solitary ctenostomes, we propose a revision of the family Aethozoidae to include the genera Franzenella d’Hondt, 1983, Aethozoon, Aethozooides, and two species currently affiliated to the genus Franzenella (F. monniotae and F. radicans) for which we erected the new taxon Solella gen. nov.

Transparent exopolymer particle (TEP) distribution and in situ prokaryotic generation across the deep Mediterranean Sea and nearby North East Atlantic Ocean

Transparent exopolymer particles (TEP) play a key role in ocean carbon export and structuring microbial habitats, but information on their distribution across different ocean basins and depths is scarce, particularly in the dark ocean. We measured TEP vertical distribution from the surface to bathypelagic waters in an east-to-west transect across the Mediterranean Sea (MedSea) and the adjacent North East Atlantic Ocean (NEA), and explored their physical and biological drivers. TEP ranged from 0.6 to 81.7 µg XG eq L−1, with the highest values in epipelagic waters above the deep chlorophyll maximum, and in areas near the Gibraltar and Sicily Straits. TEP were significantly related to particulate organic carbon (POC) in all basins and depth layers (epipelagic vs. deep), but the contribution of TEP to POC was higher in the NEA (85%, 79% and 67% in epi-, meso- and bathypelagic waters, respectively) than in the MedSea (from 53% to 62% in epipelagic waters, and from 45% to 48% in meso- and bathypelagic waters), coinciding with higher carbon to nitrogen particulate organic matter ratios in the NEA. The TEP connectivity between epipelagic waters and mesopelagic waters was less straightforward than between mesopelagic waters and bathypelagic waters, with a 23% and 55% of the variance in the relationship between layers explained respectively. Prokaryotes were found to be a likely net source of TEP as inferred by the significant direct relationship observed between prokaryotic heterotrophic abundance and TEP. This assumption was confirmed using experimental incubations, where prokaryotes produced TEP in concentrations ranging from 0.7 (Western Mediterranean, bathypelagic) to 232 (Western Mediterranean, mesopelagic) µg XG eq. L−1 day−1.

An onshore bathyal record of tectonics and climate cycles at the onset of the Early-Middle Pleistocene Transition in the eastern Mediterranean

Early Pleistocene (Calabrian) clays of the Lindos Bay Formation have been uplifted and are exposed today on the eastern coast of Rhodes (Hellenic forearc, Greece). The hemipelagic origin of these sediments and the excellent preservation of the microfossils they contain, make the Lindos Bay Formation a unique element in the eastern Mediterranean, which has the potential to constitute a paleoclimate referential framework of the region for the Early-Middle Pleistocene Transition (EMPT). In this context, 98 samples were collected in the type locality section of the Lindos Bay Formation. Stable isotope (δ18O, δ13C) analyses were carried out on benthic (Uvigerina peregrina) and planktonic (Globigerina bulloides) foraminifera for the interval between ∼1100 ka and ∼858 ka. We identify and continuously reconstruct the climate cycles that occurred between Marine Isotope Stages (MIS) 32 and 21. Counts of planktonic foraminifera were further carried out and allow connecting the conditions occurring locally in the surface waters with the glacial-interglacial cycles during the onset of the EMPT. While (sub)tropical taxa dominate the assemblages, glacials were associated with short-term (<∼10 kyr) influxes of temperate to subpolar species suggesting cooling and/or increasing productivity in the surface waters correlating with the deposition of sapropels in the eastern Mediterranean deep sea. Finally, planktonic/benthic foraminiferal ratios show that the section deposited at upper bathyal depths between ∼450 m and ∼150 m. During the late Early Pleistocene, the eastern coast of Rhodes has locally undergone repeated, transient and possibly very rapid vertical motions which are overprinted on a regional tectonically-forced regressive trend.

Distribution and diversity of polychaetes along a bathyal escarpment in the western Mediterranean Sea

Knowledge of the diversity of deep-sea polychaetes in the Mediterranean Sea is still scarce and fragmentary, due to the absence of comprehensive taxonomic revisions of several families, with the majority of recent works relying on higher level taxonomy. In the present work samples were collected with a box-corer along the Sardinian Slope, a bathyal escarpment area located in the western Mediterranean Sea, at seven depth levels separated from each other by a 300 m interval, ranging from 600 to 2400 m. Samples were sifted with a 0.3 mm mesh, and polychaetes were identified at the lowest taxonomic level and characterised from the biogeographic and tropho-functional point of view. Ninety-seven taxa were recorded, 60 of which identified at the species level; eight taxa are likely to be undescribed species, possibly endemic to the Mediterranean Sea, whereas another seven are reported for the first time for the Mediterranean Sea. The majority of taxa shows an Atlantic-Mediterranean or strictly Mediterranean distribution, thus confirming the similarity between Atlantic and Mediterranean deep-sea assemblages, but also the unicity of the latter. Conversely, cosmopolitan taxa, usually considered common in deep-sea assemblages, represented a minor component. The trophic guild composition of the assemblage varied along the slope, with shallower assemblages (600–900 m) including a relatively high percentage of predators and microphagous omnivores, while deeper assemblages (1500–1800 m) showed a > 90% percentage of deposit- and filter-feeders, with the 1200 m assemblage characterised by intermediate features. This outcome suggests that in the presently investigated area, the environmental conditions of shallower samples allow the stable occurrence of at least two trophic levels, whereas deeper assemblages depend mainly on organic matter coming from shallower levels and from the water column. The examined polychaete assemblages are characterised by low density and a complete absence of dominance, with the evenness index J’ ranging from 0.72 to 1; the wide ranges of the H’ index (0.50–2.67) and of Hill's N1 (1.65–14.65) suggest a high variability at low spatial scale. If compared to Atlantic deep-sea polychaete assemblages the assemblage studied shows an almost ten-fold lower organism abundance, but species diversity is only two- to four-fold lower, suggesting that biodiversity in Mediterranean deep-sea environments is possibly underestimated. Diversity of polychaete assemblages in the deep Mediterranean Sea is likely to be underestimated due to their low density, and adequate sampling strategies should be planned to have a better insight into the functioning and diversity of these communities.

Barium during the GEOTRACES GA-04S MedSeA cruise: The Mediterranean Sea Ba budget revisited

The distribution of barium (Ba) in seawater was determined in the main basins and straits of the Mediterranean Sea during the GEOTRACES GA-04S MedSeA cruise. In addition, the concentrations of Ba and radium (Ra) isotopes (228Ra) were determined in groundwaters discharging in the Mediterranean Sea. The dissolved Ba concentration increases from the inflowing Atlantic surface water (Ba ~ 45 nmol/kg) to the intermediate (Ba ~ 70 nmol/kg) and deep (Ba ~ 70–75 nmol/kg) Mediterranean Sea waters in general agreement with previously published profiles. We use these data to build a Ba budget of the Mediterranean Sea and to evaluate the role of different sources of Ba (dusts, rivers, sediments, submarine groundwater discharges, Messinian evaporites). Evaporation alone cannot account for the Ba concentration increase because salinity increases only by 8% between the Gibraltar Strait and the Eastern Basin, whereas the Ba concentration increases up to 75% between the Atlantic Water and the deep waters. Thus, the particulate Ba flux that maintains the Ba concentration gradient between the surface and the deep waters must be 10–100 times stronger than previously estimated and the net Ba loss at the Gibraltar Strait or out of the Western Basin must be balanced by external inputs to the Mediterranean Sea. Newly available data from Mediterranean rivers confirm that rivers are insufficient Ba sources to balance this budget. Using recent estimates of Saharan dust fluxes, we show that dust deposition is also a negligible Ba source, whereas it was previously considered as the main external source. Using Ba-228Ra data, we show for the first time that submarine groundwater discharges can significantly contribute to the Ba budget, but large uncertainties exist due to the high variability of the chemical composition of these groundwaters. The inputs from Messinian evaporites require to be further investigated. Ba transfer from the surface water to the intermediate and deep waters occurs through active particulate Ba cycling and/or Ba dissolution in the sediment. Our study suggests that the mean particulate Ba cycling is more intense than previously estimated.This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.

Dumping to the abyss: single-use marine litter invading bathyal plains of the Sardinian margin (Tyrrhenian Sea)

This study reports data on benthic litter abundance, composition and distribution obtained during deep-sea trawl surveys conducted along the Sardinian continental margin down to the bathyal plain, at depths comprised from 740 to 1740 m. None of the investigated sites was litter free. Density ranged from a minimum of 4 to a maximum of >1300 litter items per km2, with a mean value of 258 ± 59 items. Plastic accounted for 56% of the total collected items, followed by glass (24%), metal (10%). Most items, irrespectively of the category, were single-use items. Fish abundance in all of the investigated catches was significantly higher than the number of litter items, the weight of which was similar to the reared fish biomass. Our results confirm that anthropogenic waste has reached the deep Mediterranean Sea, and that the most recent EU legislation banning single-use plastic tools represents a timely and necessary measure.

Climate change impacts on the biota and on vulnerable habitats of the deep Mediterranean Sea

Deep sea is the largest and likely the most biologically diverse ecosystem of the world, but it is also the most unknown. The Mediterranean Sea (< 1% of the ocean surface and contains only the 0.3% of its volume) is a hot spot of marine biodiversity containing ca 7.5% of the world marine biodiversity, associated with a multitude of habitats spreading from the coast to its dark portion (e.g., coral banks, seamounts, canyons, and hydrothermal vents). Its deep-sea ecosystems are increasingly subjected to direct anthropogenic impacts (including overfishing, chemical pollution, dumping, litter, and plastics), which are often over-imposed to the increasing effects of global change. Here, are illustrated the expected impacts of shifts in the main variables such as temperature, food supply, pH, and oxygen on the deep Mediterranean Sea ecosystems. One of the most consequences is related to shifts in the quality and quantity of the inputs of organic matter to the deep seafloor. The deep Mediterranean Sea is far more oligotrophic than other oceans at equal depths, and although deep-sea biota reacts to food shortage by increasing their efficiency in its use, a decrease in food availability can have dramatic effects on its food webs. The deep Mediterranean Sea is showing a clear rise of deep-water temperatures. In the last decades, deep-water warming is accelerating at unprecedented rates, causing a significant shift in biodiversity even for variations in the order of 0.1 °C. Higher temperatures increase deep-sea metabolism, thus exacerbating the effects of food limitation. Moreover, ocean acidification reduces the calcification capacity of corals and alters their metabolism. Although it can be expected that increasing temperatures might increase the potential spread of oxygen minimum zone, so far, only hypoxic events were reported in Mediterranean Sea. The analysis of potential ecosystem vulnerability indicates that the ecosystems that are most sensitive to global change are deep-water coral systems and deep-sea plains. In addition, deep-sea canyons are also likely increasingly subjected to physical disturbance as a result of the increase in the frequency and intensity of climate-driven episodic events. Available information also suggests that biodiversity and ecosystem functioning of the deep Mediterranean Sea is undergoing dramatic changes, which result in accelerated organic matter biogeochemical cycling, miniaturization of the organisms’ size, increased metabolism, dominance of the microbial components, and mortality rates of deep-sea biota. Given the high sensitivity of the Mediterranean Sea to global change in comparison with other oceanic regions, and the vulnerability of its deep-sea habitats/ecosystems, specific policy measures are needed to protect its biodiversity, restore damaged habitats, and increase deep-sea ecosystems resistance and resilience to the ongoing impacts of global change.

Contribution of Bicarbonate Assimilation to Carbon Pool Dynamics in the Deep Mediterranean Sea and Cultivation of Actively Nitrifying and CO2-Fixing Bathypelagic Prokaryotic Consortia.

Covering two-thirds of our planet, the global deep ocean plays a central role in supporting life on Earth. Among other processes, this biggest ecosystem buffers the rise of atmospheric CO2. Despite carbon sequestration in the deep ocean has been known for a long time, microbial activity in the meso- and bathypelagic realm via the “assimilation of bicarbonate in the dark” (ABD) has only recently been described in more details. Based on recent findings, this process seems primarily the result of chemosynthetic and anaplerotic reactions driven by different groups of deep-sea prokaryoplankton. We quantified bicarbonate assimilation in relation to total prokaryotic abundance, prokaryotic heterotrophic production and respiration in the meso- and bathypelagic Mediterranean Sea. The measured ABD values, ranging from 133 to 370 μg C m−3 d−1, were among the highest ones reported worldwide for similar depths, likely due to the elevated temperature of the deep Mediterranean Sea (13–14°C also at abyssal depths). Integrated over the dark water column (≥200 m depth), bicarbonate assimilation in the deep-sea ranged from 396 to 873 mg C m−2 d−1. This quantity of produced de novo organic carbon amounts to about 85–424% of the phytoplankton primary production and covers up to 62% of deep-sea prokaryotic total carbon demand. Hence, the ABD process in the meso- and bathypelagic Mediterranean Sea might substantially contribute to the inorganic and organic pool and significantly sustain the deep-sea microbial food web. To elucidate the ABD key-players, we established three actively nitrifying and CO2-fixing prokaryotic enrichments. Consortia were characterized by the co-occurrence of chemolithoautotrophic Thaumarchaeota and chemoheterotrophic proteobacteria. One of the enrichments, originated from Ionian bathypelagic waters (3,000 m depth) and supplemented with low concentrations of ammonia, was dominated by the Thaumarchaeota “low-ammonia-concentration” deep-sea ecotype, an enigmatic and ecologically important group of organisms, uncultured until this study.

Syllidae (Annelida: Phyllodocida) from the deep Mediterranean Sea, with the description of three new species.

Despite almost two centuries of research, the diversity of Mediterranean deep-sea environments remain still largely unexplored. This is particularly true for the polychaete family Syllidae. We report herein 14 species; among them, we describe Erinaceusyllis barbarae n. sp., Exogone sophiae n. sp. and Prosphaerosyllis danovaroi n. sp. and report Parexogone wolfi San Martín, 1991, Exogone lopezi San Martín, Ceberio Aguirrezabalaga, 1996 and Anguillosyllis Day, 1963 for the first time from the Western Mediterranean, the latter based on a single individual likely belonging to an undescribed species. Moreover, we re-establish Syllis profunda Cognetti, 1955 based on type and new material. Present data, along with a critical analysis of available literature, show that Syllidae are highly diverse in deep Mediterranean environments, even though they are rarely reported, probably due to the scarce number of studies devoted to the size-fraction of benthos including deep-sea syllids. Most deep-sea Syllidae have wide distributions, which do not include shallow-waters. 100 m depth apparently represents the boundary between the assemblages dominated by generalist shallow water syllids like Exogone naidina Ørsted, 1843 and Syllis parapari San Martín López, 2000, and those deep-water assemblages characterised by strictly deep-water species like Parexogone campoyi San Martín, Ceberio Aguirrezabalaga, 1996, Parexogone wolfi San Martín, 1991 and Syllis sp. 1 (= Langerhansia caeca Katzmann, 1973).

The parasite community of the sharks Galeus melastomus, Etmopterus spinax and Centroscymnus coelolepis from the NW Mediterranean deep-sea in relation to feeding ecology and health condition of the host and environmental gradients and variables

The parasite communities of sharks have been largely neglected despite the ecological importance and vulnerability of this group of fishes. The main goal of the present study is to describe the parasite communities of three deep-dwelling shark species in the NW Mediterranean. A total of 120 specimens of Galeus melastomus, 11 Etmopterus spinax and 10 Centroscymnus coelolepis were captured at 400–2200m depth at two seasons and three localities off the mainland and insular slopes of the Balearic Sea. Environmental and fish biological, parasitological, dietary, enzymatic and histological data were obtained for each specimen, and the relationships among them tested. For G. melastomus, E. spinax and C. coelolepis a total of 15, two and eight parasite species were respectively recovered. The parasite community of G. melastomus is characterized by high abundance, richness and diversity, and the cestodes Ditrachybothridium macrocephalum and Grillotia adenoplusia dominate the infracommunities of juvenile and adult specimens, respectively. A differentiation of parasite communities, linked to a diet shift, has been observed between ontogenic stages of this species. E. spinax displays a depauperate parasite community, and that of C. coelolepis, described for the first time, shows moderate richness and diversity. Detailed parasite-prey relationships have been discussed and possible transmission pathways suggested for the three hosts. Parasites were mostly related to high water turbidity and O2 levels, which enhance zooplankton proliferation and could thus enhance parasite transmission. The nematodes Hysterothylacium aduncum and Proleptus obtusus were linked to high salinity levels, as already reported by previous studies, which are associated to high biomass and diversity of benthic and benthopelagic crustaceans. A decrease of acetylcholinesterase activity and lower hepatosomatic index, possibly linked to infection-related stress, have been observed. Lesions associated to encapsulated larvae of G. adenoplusia have been observed in the muscle of G. melastomus, especially in the tail region, which can be indicative of the hunting strategy of its final host and may compromise the escape response of G. melatomus thus facilitating parasite transmission.

Rapid Response of Eastern Mediterranean Deep Sea Microbial Communities to Oil

Deep marine oil spills like the Deepwater Horizon (DWH) in the Gulf of Mexico have the potential to drastically impact marine systems. Crude oil contamination in marine systems remains a concern, especially for countries around the Mediterranean Sea with off shore oil production. The goal of this study was to investigate the response of indigenous microbial communities to crude oil in the deep Eastern Mediterranean Sea (E. Med.) water column and to minimize potential bias associated with storage and shifts in microbial community structure from sample storage. 16S rRNA amplicon sequencing was combined with GeoChip metagenomic analysis to monitor the microbial community changes to the crude oil and dispersant in on-ship microcosms set up immediately after water collection. After 3 days of incubation at 14 °C, the microbial communities from two different water depths: 824 m and 1210 m became dominated by well-known oil degrading bacteria. The archaeal population and the overall microbial community diversity drastically decreased. Similarly, GeoChip metagenomic analysis revealed a tremendous enrichment of genes related to oil biodegradation, which was consistent with the results from the DWH oil spill. These results highlight a rapid microbial adaption to oil contamination in the deep E. Med., and indicate strong oil biodegradation potential.

Functional response to food limitation can reduce the impact of global change in the deep‐sea benthos

AbstractAimA key paradigm of deep‐sea ecology is that the ocean interior is a food‐limited environment, which limits the faunal growth. Here, we estimated the efficiency of deep‐sea fauna in exploiting resources to assess the potential response of deep‐sea organisms to changes in the food inputs expected with global change.LocationMediterranean Sea.Time period1989–2010.Major taxa studiedViruses, prokaryotes, meiofauna, macrofauna and megafauna.MethodsUsing the largest data set spanning from microbes to megafauna produced synoptically so far, we investigated patterns of abundance, biomass and ecosystem efficiency across depth‐related and longitudinal gradients of food availability in both Western and Eastern Basins of the Mediterranean Sea.ResultsOur results revealed that prokaryotes dominated benthic biomass at depths &gt; 2,000 m. Contrary to what has been reported at a global scale, meiofaunal biomass decreased with increasing water depth more rapidly than macrofauna and megafauna. Meiofauna showed a significant negative log‐linear relationship with increasing water depth in the whole Mediterranean Sea, whereas the other benthic components, from viruses to megafauna, did not decrease significantly, decreased or even increased (e.g., prokaryotes) with increasing water depth. Taking all components together, the efficiency of benthic ecosystems in exploiting organic carbon (OC) inputs increased with increasing depth, in both mesotrophic and ultra‐oligotrophic conditions of the deep Mediterranean Sea.Main conclusionsChanges in ecological efficiency in exploiting the energy available in food‐limited conditions suggest that deep‐sea ecosystems can show a responsive adaptation to changes in OC inputs from the photic zone. Our results contribute to explaining the high efficiency of resource exploitation by consumers in limited trophic conditions and allow us to hypothesize that the consequences of a potential reduction of food supply in deep‐sea ecosystems induced by global changes could be less severe than expected.

Asperentin B, a New Inhibitor of the Protein Tyrosine Phosphatase 1B.

In the frame of studies on secondary metabolites produced by fungi from deep-sea environments we have investigated inhibitors of enzymes playing key roles in signaling cascades of biochemical pathways relevant for the treatment of diseases. Here we report on a new inhibitor of the human protein tyrosine phosphatase 1B (PTP1B), a target in the signaling pathway of insulin. A new asperentin analog is produced by an Aspergillus sydowii strain isolated from the sediment of the deep Mediterranean Sea. Asperentin B (1) contains an additional phenolic hydroxy function at C-6 and exhibits an IC50 value against PTP1B of 2 μM in vitro, which is six times stronger than the positive control, suramin. Interestingly, asperentin (2) did not show any inhibition of this enzymatic activity. Asperentin B (1) is discussed as possible therapeutic agents for type 2 diabetes and sleeping sickness.