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The carbon and nitrogen isotopic compositions of fractions of the seagrass Posidonia oceanica (L.) Delile in a Mediterranean shallow environment (Stagnone di Marsala, western Sicily) were investigated seasonally throughout 1998. The stable isotope ratios of seagrass leaves (intermediate and adult), rhizomes, leaf litter and aegagropiles were compared over 1 year in order to distinguish between seasonal and plant part variability. Significant differences in the isotopic composition tested using ANOVA were observed as a function of both plant fraction and season. There was an overall trend towards less discrimination against 13C in summer (average δ13C ∼ −10‰) than in winter (average δ13C ∼ −13‰). In contrast, greater δ15N enrichment was observed in winter (average ∼ 5‰) than in summer (average ∼ 3‰). The possibility of a link between δ13C and δ15N seasonal variability and seagrass physiology such as plant carbon balance and reserve dynamics is proposed to explain the observed patterns. The demonstration of seasonal and plant fraction variability in P. oceanica isotopic composition provides a broader perspective to seagrass ecological and physiological studies. Overall, the observed variability can be up to 4 and 5‰ for δ13C and δ15N, respectively, a range that largely exceeds that associated with the transition between consecutive trophic levels (1 and 3.5‰ for δ13C and δ15N, respectively).Our results corroborate the need for, at least, seasonal sampling designs to obtain a good understanding of organic matter fluxes into food webs and highlight the limitations in drawing general conclusions about food webs where a low seasonal sampling effort has been applied. They also suggest that stable carbon and nitrogen isotope ratios deserve attention as a possible valuable approach in seagrass ecophysiological studies. [Copyright &y& Elsevier]

Coastal lagoons are characterized by high habitat heterogeneity where natural habitats coexist with artificial ones, historically set up to support human activities. Increasing anthropogenic pressure may lead to progressive degradation of the most vulnerable lagoonal habitats and the associated biological communities. One of the strictly estuarine-dependent fish species that may be affected by the degradation of lagoon habitats is the South European toothcarp Aphanius fasciatus , archetype of Mediterranean lagoon residents. Carbon and nitrogen stable isotopes were used to disentangle the influence of habitat types (natural vs artificial) and fish community (multi-trophic context) on the trophic niche features of A. fasciatus. Fish communities and organic matter sources were sampled in two Mediterranean lagoons located at the northernmost (Lagoon of Venice) and at the mid-latitude (Stagnone di Marsala, Trapani) of A. fasciatus distribution. Results showed evidence of high trophic adaptability of A. fasciatus , whose omnivorous feeding habit resulted in seasonal changes in isotopic niche width and niche partitioning with co-occurring species, constituting an advantage in habitats characterized by high seasonal variation of resources availability. Furthermore, while macrophytes drove the main trophic pathways leading to A. fasciatus in natural habitats, artificial habitats were mainly based on sedimentary organic matter routes. These outcomes broaden our knowledge on how natural and artificial habitats trophically support A. fasciatus populations and results are discussed in light of the ecological implications for environmental management of coastal lagoons. • Aphanius fasciatus may be affected by the degradation of coastal lagoon habitats. • Trophic niche of the species was assessed across lagoon habitats. • A. fasciatus showed high trophic adaptability across habitat types. • Trophic pathways differed between natural and artificial habitats. • Both natural and artificial habitats are crucial for A. fasciatus conservation. [ABSTRACT FROM AUTHOR]

Cyclothone braueri (Stomiiformes, Gonostomatidae) is a widely distributed fish inhabiting the mesopelagic zone of marine tropical and temperate waters. Constituting one of the largest biomasses of the ocean, C. braueri is a key element in most of the ecological processes occurring in the twilight layer. We focused on the ecological processes linked to early life stages in relation to marine pelagic environmental drivers (temperature, salinity, food availability and geostrophic currents) considering different regions of the Central Mediterranean Sea. A multivariate morphometric analysis was carried out using six parameters with the aim of discerning different larval morphotypes, while a fragment of 367 bp representing the 12S ribosomal RNA gene was used to perform molecular analyses aimed at determining the intraspecific genetic variability. Analysis highlighted two geographically distinct morphotypes not genetically discernible and related to the different nutritional conditions due to spatial heterogeneities in terms of temperature and food availability. The body depth (BD) emerged as an appropriate morphometric parameter to detect the larval condition in this species. Molecular analysis highlighted a moderate genetic divergence in the fish population, showing the recurrence of two phylogroups not geographically separated. • Two larval morphotypes not genetically discernible were found in the regions. • Larval morphotypes were related to temperature and trophic conditions. • The body diameter emerged as an appropriate parameter to detect the larval condition. • Molecular analysis evidenced not geographically separated haplogroups. [ABSTRACT FROM AUTHOR]

Ocean acidification may affect fish mineralized structures (i.e. otoliths and skeleton). Here, we compared the elemental composition of muscle and skeleton and the mineral features of skeleton in the site-attached fish Gobius bucchichi naturally exposed to high p CO 2 /low pH conditions in a shallow CO 2 vent with fish of the same species exposed to normal pH. Overall, no skeleton malformations were found in both pH conditions, but among-site differences were found in the elemental composition. Interestingly, higher Ca/P values, inducing a moderate skeleton maturation, were found in fish exposed to acidified conditions than in controls. Our findings suggest that ocean acidification may play a significant role in physiological processes related to mineralization, fostering skeleton pre-aging. Unlabelled Image • CO 2 vents are natural laboratories to study the effects of multiple pressures (ocean acidification and metal contamination). • The demersal and highly territorial fish species Gobius bucchichi did not show skeletal malformations in the vent site. • Higher Ca/P in fish skeleton at vent than control pH sites suggests that skeleton maturation speed up in acidified oceans. [ABSTRACT FROM AUTHOR]

Understanding the response of species to disturbance and the ability to recover is crucial for preventing their potential collapse and ecosystem phase shifts. Explosive submarine activity, occurring in shallow volcanic vents, can be considered as a natural pulse disturbance, due to its suddenness and high intensity, potentially affecting nearby species and ecosystems. Here, we present the response of Posidonia oceanica, a long-lived seagrass, to an exceptional submarine volcanic explosion, which occurred in the Aeolian Archipelago (Italy, Mediterranean Sea) in 2002, and evaluate its resilience in terms of time required to recover after such a pulse event. The study was carried out in 2011 in the sea area off Panarea Island, in the vicinity of Bottaro Island by adopting a back-dating methodological approach, which allowed a retrospective analysis of the growth performance and stable carbon isotopes (δ13C) in sheaths and rhizomes of P. oceanica , during a 10-year period (2001–2010). After the 2002 explosion, a trajectory shift towards decreasing values for both growth performance and δ13C in sheaths and rhizomes was observed. The decreasing trend reversed in 2004 when recovery took place progressively for all the analysed variables. Full recovery of P. oceanica occurred 8 years after the explosive event with complete restoration of all the variables (rhizome growth performance and δ13C) by 2010. Given the ecological importance of this seagrass in marine coastal ecosystems and its documented large-scale decline, the understanding of its potential recovery in response to environmental changes is imperative. • We studied resilience of Posidonia oceanica after a natural pulse disturbance. • We carried out a 10-year retrospective analysis of growth, and sheath and rhizome δ13C. • Growth performance and δ13C decreased soon after disturbance. • The decreasing trend reversed 2 years after disturbance. • Full recovery occurred 8 years after disturbance. [ABSTRACT FROM AUTHOR]

Shallow CO 2 vents are used to test ecological hypotheses about the effects of ocean acidification (OA). Here, we studied fish assemblages associated with Cymodocea nodosa meadows exposed to high p CO 2 /low pH conditions at a natural CO 2 vent in the Mediterranean Sea. Using underwater visual census, we assessed fish community structure and biodiversity in a low pH site (close to the CO 2 vent), a close control site and a far control site, hypothesising a decline in biodiversity and a homogenization of fish assemblages under OA conditions. Our findings revealed that fish diversity did not show a unique spatial pattern, or even significant relationships with pH, but correlated with seagrass leaf canopy. Among-site similarity was found in the abundance of juveniles, contrary to the expected impacts of OA on early life stages. However, pH seems an important driver in structuring fish assemblage in the low pH site, despite its high similarity with the close control site. This unexpected pattern may represent a combined response of fish mobility, enhanced food resources in the acidified site, and a 'recovery area' effect of the adjacent control site. • pH played a role in shaping nekto-benthic fish assemblages. • Fish diversity did not show unique spatial patterns or significant pH-relations. • Species richness and abundance correlated with seagrass canopy, regardless of pH. • Unexpected among-site similarity was found in the abundance of juveniles. • The area close to low pH site seems to work as a recovery area for fish. [ABSTRACT FROM AUTHOR]

In the Mediterranean Sea, brown macroalgae represent the dominant species in intertidal and subtidal habitats. Despite conservation efforts, these canopy-forming species showed a dramatic decline, highlighting the urge for active intervention to regenerate self-sustaining populations. For this reason, the restoration of macroalgae forests through transplantation has been recognized as a promising approach. However, the potential stress caused by the handling of thalli has never been assessed. Here, we used a manipulative approach to assess the transplant-induced stress in the Mediterranean Ericaria amentacea , through the analysis of biochemical proxies, i.e., phenolic compounds, lipids, and fatty acids in both transplanted and natural macroalgae over time. The results showed that seasonal environmental variability had an important effect on the biochemical composition of macroalgae, suggesting the occurrence of acclimation responses to summer increased temperature and light irradiance. Transplant-induced stress appears to have only amplified the biochemical response, probably due to increased sensitivity of the macroalgae already subjected to mechanical and osmotic stress (e.g., handling, wounding, desiccation). The ability of E. amentacea to cope with both environmental and transplant-induced stress highlights the high plasticity of the species studied, as well as the suitability of transplantation of adult thalli to restore E. amentacea beds.

Shallow water hydrothermal vents represent highly dynamic environments where strong geochemical gradients can shape microbial communities. Recently, these systems are being widely used for investigating the effects of ocean acidification on biota as vent emissions can release high CO 2 concentrations causing local pH reduction. However, other gas species, as well as trace elements and metals, are often released in association with CO 2 and can potentially act as confounding factors. In this study, we evaluated the composition, diversity and inferred functional profiles of microbial biofilms in Levante Bay (Vulcano Island, Italy, Mediterranean Sea), a well-studied shallow-water hydrothermal vent system. We analyzed 16S rRNA transcripts from biofilms exposed to different intensity of hydrothermal activity, following a redox and pH gradient across the bay. We found that elevated CO 2 concentrations causing low pH can affect the response of bacterial groups and taxa by either increasing or decreasing their relative abundance. H 2 S proved to be a highly selective factor shaping the composition and affecting the diversity of the community by selecting for sulfide-dependent, chemolithoautotrophic bacteria. The analysis of the 16S rRNA transcripts, along with the inferred functional profile of the communities, revealed a strong influence of H 2 S in the southern portion of the study area, and temporal succession affected the inferred abundance of genes for key metabolic pathways. Our results revealed that the composition of the microbial assemblages vary at very small spatial scales, mirroring the highly variable geochemical signature of vent emissions and cautioning for the use of these environments as models to investigate the effects of ocean acidification on microbial diversity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Sciutteri, Smedile, Vizzini, Mazzola and Vetriani.)

Mediterranean Sea is among the world's leading tourist destinations; however, the sharp increase in tourists during the high season may affect coastal seawater. The main aim of this study was to evaluate the occurrence and temporal variation of anthropogenic nutrients in coastal seawater in relation to tourist flows in three Mediterranean islands (Cyprus, Sicily and Rhodes), through short-term macroalgae deployments, coupled with δ 15 N analysis and GIS mapping. In all islands, an overall increase in macroalgae δ 15 N occurred over the deployment carried out in August in the tourist sites, suggesting the presence of anthropogenic nutrients. Decreasing δ 15 N values occurred at increasing distance from the coastline in two out of the three islands (Cyprus and Sicily). This study revealed the usefulness of the approach used in the assessment of tourism impact in terms of trophic enrichment and its potential to support competent authorities for the development of sustainable coastal management plans., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Despite a vast amount of literature has focused on trace element (TE) contamination in Antarctica during the last decades, the assessment of the main pathways driving TE transfer to the biota is still an overlooked issue. This limits the ability to predict how variations in sea-ice dynamics and productivity due to climate change will affect TE allocation in the food web. Here, food web structure of Tethys Bay (Terra Nova Bay, Ross Sea, Antarctica) was first characterised by analysing carbon and nitrogen stable isotopes (δ 13 C, δ 15 N) in organic matter sources (sediment and planktonic, benthic and sympagic primary producers) and consumers (zooplankton, benthic invertebrates, fish and birds). Diet and trophic position were also characterised using Bayesian mixing models. Then, relationships between stable isotopes, diet and TEs (Cd, Cr, Co, Cu, Hg, Ni, Pb and V) were assessed in order to evaluate if and how horizontal (organic matter pathways) and vertical (trophic position) food web features influence TE transfer to the biota. Regressions between log[TE] and δ 13 C revealed that the sympagic pathway drives accumulation of V in primary consumers and Cd and Hg in secondary consumers, and that a coupled benthic/pelagic pathway drives Pb transfer to all consumers. Regressions between log[TE] and δ 15 N showed that only Hg biomagnifies across trophic levels, while all the others TEs showed a biodilution pattern, consistent with patterns observed in temperate food webs. Although the Cd behavior needs further investigations, the present findings provide new insights about the role of basal sources in the transfer of TEs in polar systems. This is especially important nowadays in light of the forecasted trophic changes potentially resulting from climate change-induced modification of sea-ice dynamics., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Microbial communities of coastal marine sediment play a key role in degradation of petroleum contaminants. Here the bacterial and archaeal communities of sub-surface sediments (5-10 cm) of the chronically polluted Priolo Bay (eastern coast of Sicily, Italy), contaminated mainly by n-alkanes and biodegraded/weathered oils, were characterized by cultural and molecular approaches. 16S-PCR-DGGE analysis at six stations, revealed that bacterial communities are highly divergent and display lower phylogenetic diversity than the surface sediment; sub-surface communities respond to oil supplementation in microcosms with a significant reduction in biodiversity and a shift in composition; they retain high biodegradation capacities and host hydrocarbon (HC) degraders that were isolated and identified. HC-degrading Alfa, Gamma and Epsilon proteobacteria together with Clostridia and Archaea are a common feature of sub-surface communities. These assemblages show similarities with that of subsurface petroleum reservoirs also characterized by the presence of biodegraded and weathered oils where anaerobic or microaerophilic syntrophic HC metabolism has been proposed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Total mercury (T-Hg) and cadmium (Cd) were measured in twenty species of fish to study their bioaccumulation patterns and trophodynamics in the Augusta Bay food web. Adult and juvenile fish were caught in 2012 in Priolo Bay, south of the Augusta harbour (Central Mediterranean Sea), which is known for the high trace element and polycyclic aromatic hydrocarbon contamination level. T-Hg concentration was found to significantly increase along δ 15 N and from pelagic to benthic sedentary fish, revealing a marked influence of trophic position and habitat use (sensu Harmelin 1987) on T-Hg accumulation within ichthyofauna. Cd showed the opposite pattern, in line with the higher trace element (TE) excretion rates of high trophic level fish and the lower level of Cd environmental contamination. Trophic pathways were first characterised in the Priolo Bay food web using carbon and nitrogen stable isotopes (δ 13 C, δ 15 N) and a single main trophic pathway characterised the Priolo Bay food web. Biomagnification was then assessed, including basal sources (surface sediment, macroalgae), zooplankton, benthic invertebrates and fish. T-Hg and Cd were found to biomagnify and biodilute respectively based on the significant linear regressions between log[T-Hg] and log[Cd] vs. δ 15 N of sources and consumers and the trophic magnification factors (TMFs) of 1.22 and 0.83 respectively. Interestingly, different Cd behaviour was found considering only the benthic pathway which leads to the predatory gastropod Hexaplex trunculus. The positive slope and the higher TMF indicated active biomagnification in this benthic food web due to the high bioaccumulation efficiency of this benthic predator. Our findings provide new evidences about the role of Priolo sediments as a sources of pollutants for the food web, representing a threat to fish and, by domino effect, to humans., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

High sediment contamination in the coastal area of Priolo Bay, adjacent to the highly-polluted Augusta Harbour, poses serious risks for the benthic communities inhabiting the area. Nevertheless, the transfer of trace elements and consequent bioaccumulation in the biota is an overlooked issue. This study aimed to assess the transfer and bioaccumulation patterns of As, Cd, Ni and Hg to the dominant macroalgae and benthic invertebrates of Priolo Bay. Results revealed different patterns among trace elements (TEs), not driven by sediment contamination but rather by element-specific behaviour coupled with sediment physicochemical properties. Specifically, As accumulated in macroalgae but not in invertebrates, indicating bioavailability of dissolved As only, and a lack of effective trophic transfer. Ni was confined to surface sediment and transfer to biota was not highlighted. Cd and Hg showed the highest concentrations in invertebrates and bioaccumulated especially in filter feeders and carnivores, revealing the importance of suspended particulate and diet as transfer pathways. Total organic carbon (TOC), fine-grained sediments and redox potential were the most important sediment features in shaping the sediment contamination spatial patterns as well as those of TE transfer and bioaccumulation. In particular, As and Cd transfer to macroalgae, and especially Hg bioaccumulation in benthic invertebrates was controlled by sediment properties, resulting in limited transfer and accumulation in the most contaminated stations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Posidonia oceanica mat is considered a long-term bioindicator of contamination. Storage and sequestration of trace elements and organic carbon (C org ) were assessed in dead P. oceanica mat and bare sediments from a highly polluted coastal marine area (Augusta Bay, central Mediterranean). Sediment elemental composition and sources of organic matter have been altered since the 1950s. Dead P. oceanica mat displayed a greater ability to bury and store trace elements and C org than nearby bare sediments, acting as a long-term contaminant sink over the past 120 yr. Trace elements, probably associated with the mineral fraction, were stabilized and trapped despite die-off of the overlying P. oceanica meadow. Mat deposits registered historic contamination phases well, confirming their role as natural archives for recording trace element trends in marine coastal environments. This sediment typology is enriched with seagrass-derived refractory organic matter, which acts mainly as a diluent of trace elements. Bare sediments showed evidence of inwash of contaminated sediments via reworking; more rapid and irregular sediment accumulation; and, because of the high proportions of labile organic matter, a greater capacity to store trace elements. Through different processes, both sediment typologies represent a repository for chemicals and may pose a risk to the marine ecosystem as a secondary source of contaminants in the case of sediment dredging or erosion. Environ Toxicol Chem 2017;36:49-58. © 2016 SETAC., (© 2016 SETAC.)

A microbiological survey of the Priolo Bay (eastern coast of Sicily, Ionian Sea), a chronically polluted marine coastal area, was carried out in order to discern its intrinsic bioremediation potential. Microbiological analysis, 16S rDNA-based DGGE fingerprinting and PLFAs analysis were performed on seawater and sediment samples from six stations on two transects. Higher diversity and variability among stations was detected by DGGE in sediment than in water samples although seawater revealed higher diversity of culturable hydrocarbon-degrading bacteria. The most polluted sediment hosted higher total bacterial diversity and higher abundance and diversity of culturable HC degraders. Alkane- and PAH-degrading bacteria were isolated from all stations and assigned to Alcanivorax, Marinobacter, Thalassospira, Alteromonas and Oleibacter (first isolation from the Mediterranean area). High total microbial diversity associated to a large selection of HC degraders is believed to contribute to natural attenuation of the area, provided that new contaminant contributions are avoided., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Fish species have attracted considerable interest in studies assessing biological responses to environmental contaminants. In this study, the attention has been focussed on fishbone of selected fish species from a highly polluted marine area, Augusta Bay (Italy, Central Mediterranean) to evaluate if toxicant elements had an effect on the mineralogical structure of bones, although macroscopic deformations were not evident. In particular, an attempt was made to evaluate if bone mineral features, such as crystallinity, mineral maturity and carbonate/phosphate mineral content, determined by XR-Diffraction and FT-IR Spectroscopy, suffered negative effects due to trace element levels in fishbone, detected by ICP-OES. Results confirmed the reliability of the use of diffractometric and spectroscopic techniques to assess the degree of crystallinity and the mineral maturity in fishbone. In addition, in highly polluted areas, Hg and Cr contamination induced a process of premature aging of fishbone, altering its biochemical and mineral contents., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

We investigated and compared the impact of organic loads due to the biodeposition of mussel and fish farms on the water column of a coastal area of the Tyrrhenian Sea (Western Mediterranean). Physico-chemical data (including oxygen, nutrients. DOC and particulate organic matter), microbial variables (picoplankton and picophytoplankton density and biomass) and phytoplankton biomass (as chlorophyll-a) were determined on a monthly basis from March 1997 to February 1998. The results of this study indicate that both fish farm and mussel culture did not alter significantly dissolved inorganic phosphorus and chlorophyll-a values, while inorganic nitrogen concentrations were higher in mussel farm area. However, waters overlying the fish farm presented significantly higher DOC concentrations. In contrast, no significant differences were observed comparing particulate matter concentrations. The increased DOC concentrations determined a response of the heterotrophic fraction of picoplankton, while picophytoplankton, likewise phytoplankton. did not display differences among fish or mussel farms and control site. From the analysis of the different microbial components, it is possible to conclude that the impact of fish farms is evident only for the heterotrophic components. The comparative analysis of the mussel biodeposition and fish-farm impact revealed that mussel farms induced a considerably lower disturbance, apparently limited to an increased density and biomass of microbial assemblages beneath the mussel cultures.