GLOSSary: the GLobal Ocean 16S subunit web accessible resource.

BACKGROUND: Environmental metagenomics is a challenging approach that is exponentially spreading in the scientific community to investigate taxonomic diversity and possible functions of the biological components. The massive amount of sequence data produced, often endowed with rich environmental metadata, needs suitable computational tools to fully explore the embedded information. Bioinformatics plays a key role in providing methodologies to manage, process and mine molecular data, integrated with environmental metagenomics collections. One such relevant example is represented by the Tara Ocean Project. RESULTS: We considered the Tara 16S miTAGs released by the consortium, representing raw sequences from a shotgun metagenomics approach with similarities to 16S rRNA genes. We generated assembled 16S rDNA sequences, which were classified according to their lengths, the possible presence of chimeric reads, the putative taxonomic affiliation. The dataset was included in GLOSSary (the GLobal Ocean 16S Subunit web accessible resource), a bioinformatics platform to organize environmental metagenomics data. The aims of this work were: i) to present alternative computational approaches to manage challenging metagenomics data; ii) to set up user friendly web-based platforms to allow the integration of environmental metagenomics sequences and of the associated metadata; iii) to implement an appropriate bioinformatics platform supporting the analysis of 16S rDNA sequences exploiting reference datasets, such as the SILVA database. We organized the data in a next-generation NoSQL "schema-less" database, allowing flexible organization of large amounts of data and supporting native geospatial queries. A web interface was developed to permit an interactive exploration and a visual geographical localization of the data, either raw miTAG reads or 16S contigs, from our processing pipeline. Information on unassembled sequences is also available. The taxonomic affiliations of contigs and miTAGs, and the spatial distribution of the sampling sites and their associated sequence libraries, as they are contained in the Tara metadata, can be explored by a query interface, which allows both textual and visual investigations. In addition, all the sequence data were made available for a dedicated BLAST-based web application alongside the SILVA collection. CONCLUSIONS: GLOSSary provides an expandable bioinformatics environment, able to support the scientific community in current and forthcoming environmental metagenomics analyses.

Inorganic UV filter-based sunscreens labelled as eco-friendly threaten sea urchin populations.

Although the negative effects of inorganic UV filters have been documented on several marine organisms, sunscreen products containing such filters are available in the market and proposed as eco-friendly substitutes for harmful, and already banned, organic UV filters (e.g. octinoxate and oxybenzone). In the present study, we investigated the effects of four sunscreen products, labelled by cosmetic companies as "eco-friendly", on the early developmental stages of the sea urchin Paracentrotus lividus, a keystone species occurring in vulnerable coastal habitats. Among sunscreens tested, those containing ZnO and TiO2 or their mix caused severe impacts on sea urchin embryos. We show that inorganic UV filters were incorporated by larvae during their development and, despite the activation of defence strategies (e.g. phagocytosis by coelomocytes), generated anomalies such as skeletal malformations and tissue necrosis. Conversely, the sunscreen product containing only new-generation organic UV filters (e.g. methylene bis-benzotriazolyl tetramethyl, ethylhexyl triazone, butylphenol diethylamino hydroxybenzoyl hexyl benzoate) did not affect sea urchins, thus resulting actually eco-compatible. Our findings expand information on the impact of inorganic UV filters on marine life, corroborate the need to improve the eco-friendliness assessment of sunscreen products and warn of the risk of bioaccumulation and potential biomagnification of inorganic UV filters along the marine food chain.

New sequence types and multidrug resistance among pathogenic Escherichia coli isolates from coastal marine sediments.

The spread of antibiotic-resistant microorganisms is widely recognized, but data about their sources, presence, and significance in marine environments are still limited. We examined 109 Escherichia coli strains from coastal marine sediments carrying virulence genes for antibiotic susceptibility, specific resistance genes, prevalence of class 1 and 2 integrons, and sequence type. Antibiotic resistance was found in 35% of strains, and multiple resistances were found in 14%; the resistances detected most frequently were against tetracycline (28%), ampicillin (16.5%), trimethoprim-sulfamethoxazole (13%), and streptomycin (7%). The highest prevalence of resistant strains was in phylogenetic group A, whereas phylogroup B2 exhibited a significantly lower frequency than all the other groups. Sixty percent of multiresistant strains harbored class 1 or 2 integrase genes, and about 50% carried resistance genes (particularly dfrA and aadA) linked to a class 1 integron. Multilocus sequence typing of 14 selected strains identified eight different types characteristic of extraintestinal pathogens and three new allelic combinations. Our data suggest that coastal marine sediment may be a suitable environment for the survival of pathogenic and antimicrobial-resistant E. coli strains capable of contributing to resistance spread via integrons among benthic bacteria, and they highlight a role for these strains in the emergence of new virulent genotypes.

Pollutant Pb burden in Mediterranean Centroscymnus coelolepis deep-sea sharks.

We report lead (Pb) analyses in juvenile (n = 37; mean length = 24.7 ±â€¯2.3 cm) and adult (n = 16; mean length = 52.3 ±â€¯9.3 cm) Centroscymnus coelolepis Mediterranean deep-sea sharks that are compared to Pb content in bathy-demersal, pelagic and shallow coastal sharks. Median Pb concentrations of C. coelolepis muscle (0.009-0.056 wet ppm) and liver (0.023-0.061 wet ppm) are among the lowest encountered in shark records. Stable Pb isotope imprints in adult C. coelolepis muscles highlight that most of Pb in C. coelolepis is from human origin. Lead isotopes reveal the persistence of gasoline Pb emitted in the 1970s in low-turnover adult shark's muscle while associated liver imprints are in equilibrium with recent pollutant Pb signatures suggesting an efficient pollutant Pb turnover metabolism. The comparison of Pb distribution between adult and juvenile cohorts suggests the role of dietary exposure and possible maternal offloading of Pb during gestation, likely associated to vitellogenesis in this aplacental viviparous deep-sea shark.

Environmental DNA metabarcoding for benthic monitoring: A review of sediment sampling and DNA extraction methods.

Environmental DNA (eDNA) metabarcoding (parallel sequencing of DNA/RNA for identification of whole communities within a targeted group) is revolutionizing the field of aquatic biomonitoring. To date, most metabarcoding studies aiming to assess the ecological status of aquatic ecosystems have focused on water eDNA and macroinvertebrate bulk samples. However, the eDNA metabarcoding has also been applied to soft sediment samples, mainly for assessing microbial or meiofaunal biota. Compared to classical methodologies based on manual sorting and morphological identification of benthic taxa, eDNA metabarcoding offers potentially important advantages for assessing the environmental quality of sediments. The methods and protocols utilized for sediment eDNA metabarcoding can vary considerably among studies, and standardization efforts are needed to improve their robustness, comparability and use within regulatory frameworks. Here, we review the available information on eDNA metabarcoding applied to sediment samples, with a focus on sampling, preservation, and DNA extraction steps. We discuss challenges specific to sediment eDNA analysis, including the variety of different sources and states of eDNA and its persistence in the sediment. This paper aims to identify good-practice strategies and facilitate method harmonization for routine use of sediment eDNA in future benthic monitoring.

Extraintestinal Escherichia coli carrying virulence genes in coastal marine sediments.

Despite the recognized potential of long-term survival or even growth of fecal indicators bacteria (FIB) in marine sediments, this compartment is largely ignored by health protection authorities. We conducted a large-scale study over approximately 50 km of the Marche coasts (Adriatic Sea) at depths ranging from 2 to 5 m. Total and fecal coliforms (FC) were counted by culture-based methods. Escherichia coli was also quantified using fluorescence in situ hybridization targeting specific 16S rRNA sequences, which yielded significantly higher abundances than culture-based methods, suggesting the potential importance of viable but nonculturable E. coli cells. Fecal coliforms displayed high abundances at most sites and showed a prevalence of E. coli. FC isolates (n = 113) were identified by API 20E, additional biochemical tests, and internal transcribed spacer-PCR. E. coli strains, representing 96% of isolates, were then characterized for genomic relatedness and phylogenetic group (A, B1, B2, and D) of origin by randomly amplified polymorphic DNA and multiplex-PCR. The results indicated that E. coli displayed a wide genotypic diversity, also among isolates from the same station, and that 44 of the 109 E. coli isolates belonged to groups B2 and D. Further characterization of B2 and D isolates for the presence of 11 virulence factor genes (pap, sfa/foc, afa, eaeA, ibeA, traT, hlyA, stx(1), stx(2), aer, and fyuA) showed that 90% of B2 and 65% of D isolates were positive for at least one of these. Most of the variance of both E. coli abundance and assemblage composition (>62%) was explained by a combination of physical-chemical and trophic variables. These findings indicate that coastal sediments could represent a potential reservoir for commensal and pathogenic E. coli and that E. coli distribution in marine coastal sediments largely depends upon the physical and trophic status of the sediment. We conclude that future sampling designs aimed at monitoring the microbiological quality of marine coastal areas should not further neglect the analysis of the sediment and that monitoring of these environments can be improved by including molecular methods as a complement of culture-based techniques.

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.

Anthropogenic noise and biological sounds in a heavily industrialized coastal area (Gulf of Naples, Mediterranean Sea).

Underwater noise is one of the most widespread threats to the world oceans. Its negative impact on fauna is nowadays well established, but baseline data to be used in management and monitoring programs are still largely lacking. In particular, the acoustic assessment of human-impacted marine coastal areas provides complementary information on the health status of marine ecosystems. The objective of our study was to provide a baseline of underwater noise levels and biological sounds at two sites within the Gulf of Naples (Italy), one of which is located in Bagnoli-Coroglio, a Site of National Interest (SIN) for its high contamination levels. Within the SIN, sounds were recorded both before and during sediment coring activities (vibrocorer sampling), in order to investigate the potential acoustic impact due to such operations. Acoustic recordings were analyzed following the European Marine Strategy Framework Directive indications as defined in the frame of the Descriptor 11. Results reported here show that the investigated area is characterized by a high anthropogenic noise pressure. Ambient noise levels were principally driven by shipping noise and biological sounds of invertebrates (e.g., snapping shrimps). Sounds referable to other biological activity were difficult to detect because heavily masked by shipping noise. Coring activity determined a substantial introduction of additional noise at a local spatial scale. This study expands underwater noise baseline data to be further implemented in future monitoring programs of coastal areas affected by anthropogenic impacts. In addition, it proposes new cues for using underwater acoustic monitoring tools to complement traditional methodologies for evaluating health status of ecosystems and for investigating recovery rates after restoration/reclamation programs.

Chemical contamination can promote turnover diversity of benthic prokaryotic assemblages: The case study of the Bagnoli-Coroglio bay (southern Tyrrhenian Sea).

Chemical contamination of marine ecosystems represents a major concern for the detrimental consequences at different levels of biological organization. However, the impact of chronic contamination on the diversity and assemblage composition of benthic prokaryotes is still largely unknown, and this limits our understanding of the potential implications on ecosystem functioning. The Bagnoli-Coroglio bay (Gulf of Naples, Tyrrhenian Sea) is a typical example of coastal area heavily contaminated by metals and hydrocarbons, released for decades by industrial activities, which ceased at the beginning of nineties. In the present study we analyzed the abundance, diversity and assemblage composition of benthic prokaryotic assemblages at increasing distance from the historical source of contamination in relation to the heavy hydrocarbons (C > 12), polycyclic aromatic hydrocarbons (PAHs) and heavy metal concentrations in the sediments. Prokaryotic abundance in the sediments differed among sites, and was mostly driven by environmental factors rather than by contamination levels. Conversely, the richness of prokaryotic taxa was relatively high in all samples, was driven by contamination levels and decreased significantly with increasing contamination (15-38%). Moreover, our results indicate large variations in the composition of the benthic prokaryotic assemblages among sites, mostly explained by the different levels and types of chemical contaminants found in the sediments. Overall, our findings suggest that chemical contaminants, even after decades from the end of their release, can profoundly influence the richness and turnover diversity of the benthic prokaryotic assemblages, in turn promoting a high diversification of the benthic bacterial and archaeal assemblages by selecting those lineages more adapted to specific mixtures of different contaminants. Our results open new perspectives for understanding of the long-term effects of chemical contamination on the benthic prokaryotic assemblages and the ecological processes they mediate.

Impact of historical contamination on meiofaunal assemblages: The case study of the Bagnoli-Coroglio Bay (southern Tyrrhenian Sea).

The effects of contaminants on marine organisms have been documented since decades, but the long-term responses and recovery rates of benthic communities to mixtures of contaminants, several years after the cessation of industrial activities, need to be further investigated. Bagnoli-Coroglio Bay (Gulf of Naples, Tyrrhenian Sea) is a typical example of historically contaminated coastal area due to industrial activities stopped at the beginning of nineties. In the present study we carried out a fine spatial scale analysis of the distribution of meiofaunal (and nematodes) assemblages along five bathymetric transects located at increasing distance from the historical source of contamination in relation with the polycyclic aromatic hydrocarbon and heavy metal concentrations present in the sediment. Meiofaunal abundance and biomass changed widely along transects but independent from the distance from the source of contamination. Even when the contamination levels were expected to induce significant detrimental biological consequences, meiofaunal abundance and biomass were similar to those reported in unpolluted benthic coastal areas worldwide. Conversely, biodiversity in terms of meiofaunal taxa richness was generally low (range: 5-8 taxa in 12 of the overall 15 stations investigated). This was explained by the lack of sensitive groups such as ostracods, gastrotrichs and tardigrades commonly encountered in benthic coastal ecosystems, thus reflecting an overall poor/moderate environmental quality of the investigated area. Nematode (structural and functional) diversity was also low, particularly at stations characterized by higher contamination levels. At the same time, nematode species composition did not change significantly among stations suggesting a widespread effect of contaminants able to reduce the variability (i.e., turnover diversity) within the assemblages of the whole study area. Overall, our results indicate that even decades after the cessation of contaminant emissions, benthic biodiversity was affected in terms of both meiofaunal taxa and nematode species. These findings strongly reinforce the call for reducing sources of chronic pollution in marine ecosystems and provide new insights for a better understanding of the ecological recovery of historically contaminated marine environments.

Assessing the efficiency and eco-sustainability of bioremediation strategies for the reclamation of highly contaminated marine sediments.

Coastal sediments subjected to high anthropogenic impacts can accumulate large amounts of polycyclic aromatic hydrocarbons (PAHs) and metals, demanding effective and eco-sustainable remediation solutions. In this study, we carried out bioremediation experiments on marine sediments highly contaminated with PAHs and metals. In particular, we investigated the effects of biostimulation (by the addition of inorganic nutrients), bioaugmentation (by the addition of fungi belonging to Aspergillus sp.) and microbial fuel cell-based strategies on PAH degradation and on changes in metal partitioning. Results reported here indicate that all biotreatments determined a significant decrease of PAH concentrations (at least 60%) in a relatively short time interval (few weeks) and that biostimulation was the most effective approach (>90%). Biostimulation determined a faster degradation rate of high than low molecular weight PAHs, indicating a preferential biodegradation of specific PAH congeners. At the same time, the biotreatments changed the partitioning of metals, including their solubilization, suggesting the need of parallel environmental risk assessment. Our findings also suggest that ex situ biotreatments can have a lower carbon footprint than current management options of contaminated sediments (i.e., landfill disposal and/or disposal in confined aquatic facilities), but integration with other strategies for metal removal (e.g. through bioleaching) from sediments is needed for their safe re-use. Overall, results presented here provide new insights into the development of effective and eco-sustainable bioremediation strategies for the reclamation of highly contaminated marine sediments.

Species-specific sensitivity of three microalgae to sediment elutriates.

Microalgae are considered good bioindicators of marine environmental quality. Frequently, they are used to investigate the toxicity of sediment elutriates, but their sensitivity is disputed. This paper compared the sensitivity of Phaeodactylum tricornutum (diatom), Skeletonema costatum (diatom), and Dunaliella tertiolecta (green alga), analyzing 257 samples of elutriates (1:4 sediment: water ratio), considering growth inhibition (72 h) as the reference endpoint and sediment chemical (metals, metalloids and polyaromatic hydrocarbons) and grain size. Results of the toxicity tests showed that the microalgae sensitivity was not correlated. The integration of chemical data did not allow to discriminate toxicity effects but contributed to highlight that D. tertiolecta was the most sensitive microalgae (no cell wall) followed by P. tricornutum and S. costatum. Further analysis, including lines of evidence and weight of evidence approaches to calculate risk quotients of elutriate samples, confirmed these results.

Exo-Ocean Exploration with Deep-Sea Sensor and Platform Technologies.

One of Saturn's largest moons, Enceladus, possesses a vast extraterrestrial ocean (i.e., exo-ocean) that is increasingly becoming the hotspot of future research initiatives dedicated to the exploration of putative life. Here, a new bio-exploration concept design for Enceladus' exo-ocean is proposed, focusing on the potential presence of organisms across a wide range of sizes (i.e., from uni- to multicellular and animal-like), according to state-of-the-art sensor and robotic platform technologies used in terrestrial deep-sea research. In particular, we focus on combined direct and indirect life-detection capabilities, based on optoacoustic imaging and passive acoustics, as well as molecular approaches. Such biologically oriented sampling can be accompanied by concomitant geochemical and oceanographic measurements to provide data relevant to exo-ocean exploration and understanding. Finally, we describe how this multidisciplinary monitoring approach is currently enabled in terrestrial oceans through cabled (fixed) observatories and their related mobile multiparametric platforms (i.e., Autonomous Underwater and Remotely Operated Vehicles, as well as crawlers, rovers, and biomimetic robots) and how their modified design can be used for exo-ocean exploration.

Multiple human pressures in coastal habitats: variation of meiofaunal assemblages associated with sewage discharge in a post-industrial area.

Marine ecosystems are globally threatened by human activities, but some areas, such as those affected by abandoned industrial plants, show an overlap of acute and chronic impacts, which determine a considerable deterioration of their health status. Here we report the results of a research conducted on coastal sewers that discharge their loads in the highly contaminated area of Bagnoli-Coroglio (Tyrrhenian Sea, Western Mediterranean). The sampling area is characterized by heavy industrial activities (a steel plant using coal, iron and limestone) started in 1905 and ceased in 1990, which left widespread heavy metals and hydrocarbon contamination. After taking into account the potential influence of sediment grain size ranges through their inclusion as covariates in the analysis, we tested the potential impact of sewage discharge on the total abundance and multivariate structure of meiofaunal assemblages, as well as on the abundance of single taxa. The organic matter was analysed in terms of total phytopigment and biopolymeric carbon concentrations. Nematoda, Copepoda (including their nauplii), and Tardigrada were the most abundant meiofaunal taxa at all sites, but nematodes did not show a consistent pattern relative to the sewage outfalls. However, the sewer located in the historically most contaminated area showed a minimal abundance of all taxa, including nematodes, while copepods were relatively less abundant at the two southernmost sewers. Comparing the north vs. south site of the sewers, higher meiofaunal abundances were observed in the southward part, likely as a result of the local circulation. The results of this study indicate the general adaptation of meiofauna to multiple stressors (sewage discharge, superimposed to chronic industrial contamination) and its likely modulation by other local processes. They also provide relevant baseline information for future restoration interventions that would take into account the spatial variation of target organisms as needed.

Effects of sub-seabed CO2 leakage: Short- and medium-term responses of benthic macrofaunal assemblages.

The continued rise in atmospheric carbon dioxide (CO2) levels is driving climate change and temperature shifts at a global scale. CO2 Capture and Storage (CCS) technologies have been suggested as a feasible option for reducing CO2 emissions and mitigating their effects. However, before CCS can be employed at an industrial scale, any environmental risks associated with this activity should be identified and quantified. Significant leakage of CO2 from CCS reservoirs and pipelines is considered to be unlikely, however direct and/or indirect effects of CO2 leakage on marine life and ecosystem functioning must be assessed, with particular consideration given to spatial (e.g. distance from the source) and temporal (e.g. duration) scales at which leakage impacts could occur. In the current mesocosm experiment we tested the potential effects of CO2 leakage on macrobenthic assemblages by exposing infaunal sediment communities to different levels of CO2 concentration (400, 1000, 2000, 10,000 and 20,000 ppm CO2), simulating a gradient of distance from a hypothetic leakage, over short-term (a few weeks) and medium-term (several months). A significant impact on community structure, abundance and species richness of macrofauna was observed in the short-term exposure. Individual taxa showed idiosyncratic responses to acidification. We conclude that the main impact of CO2 leakage on macrofaunal assemblages occurs almost exclusively at the higher CO2 concentration and over short time periods, tending to fade and disappear at increasing distance and exposure time. Although under the cautious perspective required by the possible context-dependency of the present findings, this study contributes to the cost-benefit analysis (environmental risk versus the achievement of the intended objectives) of CCS strategies.

Synoptic determination of living/dead and active/dormant bacterial fractions in marine sediments.

The most widely used methods for the estimation of the living/dead fractions of bacterial cells involve specific stains that are able to reveal membrane integrity. Here, we have compared two different probes (propidium iodide and ethidium homodimer-2) that have different molecular weights and steric hindrance effects. We have also combined this method with the staining/destaining procedure that is currently used in the identification of potentially active cells. The procedure for marine sediments described here allows the synoptic (i.e. from the same filter) identification of: (i) the number of living bacteria; (ii) the number of active vs. dormant cells within this living fraction; (iii) the bacterial fraction with an intact nucleoid region without membrane integrity; and (iv) dead cells (devoid of the nucleoid region and without membrane integrity). Our results demonstrate that the concentration of propidium is crucial for the correct estimation of the dead bacterial fraction, ethidium homodimer-2 allows efficient and accurate estimates that are independent of the concentrations used and the sample storage. The active bacterial fraction represented c. 40% of the total bacterial abundance, the inactive/dormant fraction c. 30%, and the dead fraction was, on average, c. 30%. This method allows the processing of a large number of samples with high precision and at relatively low cost, and thus it provides additional synoptic insights into the metabolic state of bacteria in marine sediments.

Structural and functional response of meiofauna rocky assemblages to sewage pollution.

Despite meiofauna being one of the most popular tool for detecting the ecological effects of different sources of impact, the application of structured experimental designs to this benthic component is typically neglected, especially in subtidal rocky shores. In this study, an asymmetrical design was used to detect hard-bottom meiofaunal abundance and biodiversity response to sewage discharge. Sampling was carried out at a depth of 3-4 m by SCUBA diving, by means of a modified manual corer. Six replicate cores were collected at three sites (80-100 m apart), at each of three locations (one purportedly impacted [I] and two controls [Cs]). A total of 84,994 specimens were collected. The outfall affected meiofaunal assemblages in terms of taxon richness, by determining a significant reduction of the number of taxa in the disturbed location, and community structure, by causing functional changes in terms of a decrease of the abundance of nematodes and an increase of the hydrozoan component. Nematodes and syllid polychaetes showed significant lower average abundance at I. Multivariate analyses showed that both meiofaunal assemblage and syllids were significantly different at I compared with Cs. The sewage outfall also affected patterns of spatial distribution at the scale of site (100 m apart) and of replicate units (centimetres apart), both in syllids and in nematodes. Our results provide evidence that the selection of multiple controls is crucial to prevent the widespread risk of Type II error, highlighting the need of more accurate experimental designs when dealing with meiofauna.

Impact of offshore gas platforms on the structural and functional biodiversity of nematodes.

The Mediterranean Sea hosts hundreds of offshore gas platforms, whose activity represents a potential threat to marine ecosystems. Evidence from several studies indicates that nematodes can be highly sensitive to changes in the environmental quality. Here, we investigated the response of nematode assemblages to the presence of offshore gas platforms (located in the central Mediterranean Sea) in terms of spatial heterogeneity, structural and functional diversity. Since the effect of the investigated offshore platforms on macrofaunal assemblages were previously assessed by Terlizzi et al. (2008), the study provided also the opportunity to compare the response of different benthic compartments to the same impact related to fossil fuel extraction on marine environments. The platforms had a significant impact on nematode assemblages up to 1000 m distance from the structure. The effects were evident in term of: a) more homogeneous spatial distribution of nematode assemblages, b) increased trophic diversity of deposit feeders and c) changes in life strategies with an increase of opportunistic species in sediments closer to the platforms. Such effects seemed to be related to the dimension of the platform structures, rather than to chemical pollution or changes in food availability. These findings suggest that the platforms exert a physical alteration of the surrounding environment that is reflected by altered structural and functional traits of nematode biodiversity. The use of nematodes for monitoring the effects of the platforms only partially matched with the results obtained using macrofauna, providing further insights on potential outcomes on the functional response of marine assemblages to fossil fuel extraction.

Exo-enzymatic activities and dissolved organic pools in relation with mucilage development in the Northern Adriatic Sea.

We tested the hypothesis that the appearance of mucilage in the Northern Adriatic Sea was related with the accumulation of dissolved organic compounds released by intensive enzymatic activities and not utilized as direct substrate for microbial growth. To do this enzymatic activities and dissolved organic and inorganic pools in periods characterized by the presence of mucilage and in the same seasons but in absence of mucilage were compared. Extracellular enzymatic activities (aminopeptidase, beta-glucosidase and alkaline phosphatase), nutrient pool concentrations (total dissolved nitrogen, dissolved organic nitrogen, total dissolved phosphorus, dissolved organic phosphorus) and the biochemical composition of particulate and dissolved organic matter (in terms of proteins and carbohydrates) were determined on a monthly basis over a period of 3 years. Aminopeptidase and alkaline phosphatase activities displayed higher values in springs preceding the appearance of mucilage than in spring when no mucilage was observed. Beta-Glucosidase activity showed significantly higher values in summer periods characterized by the massive production of mucilage than in summers without mucilage events. The months preceding mucilage events were also characterized by an increase of the alkaline phosphatase to aminopeptidase activity ratio and by a significant accumulation of dissolved proteins. These findings, together with the significant increase of the DON/DOP ratio, suggest that mucilage formation is favoured by the deficiency of organic P. The present study provides compelling evidences that mucilage formation is favoured by the unbalance between organic matter mobilization by enzymatic activities and the accumulation of labile dissolved organic-N compounds.

Enzymatic activity, bacterial distribution, and organic matter composition in sediments of the ross sea (Antarctica)

Enzymatic activities of aminopeptidase and beta-glucosidase were investigated in Antarctic Ross Sea sediments at two sites (sites B and C, 567 and 439 m deep, respectively). The sites differed in trophic conditions related to organic matter (OM) composition and bacterial distribution. Carbohydrate concentrations at site B were about double those at site C, while protein and lipid levels were 10 times higher. Proteins were mainly found in a soluble fraction (>90%). Chloropigment content was generally low and phaeopigments were almost absent, indicating the presence of reduced inputs of primary organic matter. ATP concentrations (as a measure of the living microbial biomass) were significantly higher at site B. By contrast, benthic bacterial densities at site C were about double those at site B. Bacterial parameters do not appear to be "bottom-up controlled" by the amount of available food but rather "top-down controlled" by meiofauna predatory pressure, which was significantly higher at site B. Aminopeptidase and beta-glucosidase extracellular enzyme activities (EEA) in Antarctic sediments appear to be high and comparable to those reported for temperate or Arctic sediments and characterized by low aminopeptidase/beta-glucosidase ratios (about 10). Activity profiles showed decreasing patterns with increasing sediment depth, indicating vertical shifts in both availability and nutritional quality of degradable OM. Vertical profiles of aminopeptidase activity were related to a decrease in protein concentration and/or to an increase in the insoluble refractory proteinaceous fraction. The highest aminopeptidase activity rates were observed at site C, characterized by much lower protein concentrations. Differences in EEA between sites do not seem to be explained by differences in the in situ temperature (-1.6 and -0.8 degreesC at sites B and C, respectively). Aminopeptidase activity profiles are consistent with the bacterial biomass and frequency of dividing cells. Enzyme substrate affinity was generally dependent upon substrate concentrations. EEA, normalized to bacterial numbers, indicated specific activities comparable to those reported for equally deep sediments at temperate latitudes. Vertical patterns of specific enzymatic activity appeared to be controlled by chloroplastic pigment concentrations that accumulate in the deeper sediment layers. The overall conclusion from the analysis of EEA in Antarctic sediments is that enzyme-dependent transformations of OM proceed at rates similar to those measured in temperate environments. Protein carbon potentially liberated by aminopeptidase activities (12.597 to 26.190 mg of C m-2 day-1) indicates that the whole protein pool could be mobilized within 1.3 to 17 h. Carbohydrate carbon mobilization (773 to 2,552 mg of C m-2 day-1) is sufficient to turn over the carbohydrate pool within 16 to 20 h. Such rates are 6 to 45 times higher than fluxes of particulate organic proteins and carbohydrates, indicating an "uncoupled hydrolysis" by the Antarctic benthic assemblages, in which bacteria appear to be able to rapidly exploit episodic OM pulses.