Coastal sediments constitute a major reservoir for natural and anthropogenic mercury (Hg) and can be used as geochronological records of past Hg deposition. They may also act as secondary Hg sources ...for pelagic ecosystems via the efflux of toxic methylmercury (MeHg) diffusing from sediment porewaters and/or mobilized by sediment resuspension. In Toulon Bay sediments, which are known as one of the Hg hot spots of the northwestern Mediterranean Sea, we explored Hg species accumulation and mobility. The total Hg concentrations averaged 0.014 μg g−1 ca. 2000 years ago, then exhibited three major peaks during the Medieval Period, the Early Modern Period of Europe, and the Industrial Era, reaching 0.06, 0.07, and 13 μg g−1, respectively. The Medieval peak is attributed to the massive development of metallurgy in Europe accompanied by the burning of soil and vegetation, the second peak to the optimum of Hg extraction in Europe (Almadén mine), and the resumption of deforestation after the great plague. The third most recent Hg enrichment is associated with Hg-fulminate production, the scuttling of the French navy fleet during World War II, and ship salvaging and removal in the post-war years. Sampling of the dissolved phase at high vertical resolution above and below the sediment-water interface (SWI) enables us to conclude that MeHg was produced in situ by microbiological pathways and its diffusion across the SWI was negligible. On the other hand, ex-situ resuspension experiments showed that sorption and/or photodemethylation restrict MeHg from the dissolved phase.
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•Hg species sources, accumulation, and mobility were studied in contaminated coastal sediments.•Hg peaked during the Medieval Period, the Early Modern Period of Europe, and the Industrial Era.•MeHg is microbiologically produced in the sediments.•MeHg and HgT diffusions across the sediment-water interface were negligible.
Despite the recognized important ecological role that cetaceans play in the marine environment, their protection is still scarcely enforced in the Mediterranean Sea even though this area is strongly ...threatened by local human pressures and climate change. The piecemeal of knowledge related to cetaceans' ecology and distribution in the basin undermines the capacity of addressing cetaceans' protection and identifying effective conservation strategies. In this study, an Ecosystem-Based Marine Spatial Planning (EB-MSP) approach is applied to assess human pressures on cetaceans and guide the designation of a conservation area in the Gulf of Taranto, Northern Ionian Sea (Central-eastern Mediterranean Sea). The Gulf of Taranto hosts different cetacean species that accomplish important phases of their life in the area. Despite this fact, the gulf does not fall within any area-based management tools (ABMTs) for cetacean conservation. We pin down the Gulf of Taranto being eligible for the designation of diverse ABMTs for conservation, both legally and non-legally binding. Through a risk-based approach, this study explores the cause-effect relationships that link any human activities and pressures exerted in the study area to potential effects on cetaceans, by identifying major drivers of potential impacts. These were found to be underwater noise, marine litter, ship collision, and competition and disturbance on preys. We draw some recommendations based on different sources of available knowledge produced so far in the area (i.e., empirical evidence, scientific and grey literature, and expert judgement) to boost cetaceans’ conservation. Finally, we stress the need of sectoral coordination for the management of human activities by applying an EB-MSP approach and valuing the establishment of an ABMT in the Gulf of Taranto.
•Cetaceans' conservation addressed through a risk-based approach.•Evidence collected from multiple knowledge sources and uncertainty analysed.•Multiple drivers of pressures from maritime and land-based activities identified.•Cause-effects analysis of direct and indirect pressures on cetaceans developed.•Ecosystem-based MSP suitable to control pressures from activities outside MPAs.
Accurate age estimates for fish are critical for properly understanding stock dynamics and health; this is particularly true for larger billfishes. Here we determined the most accurate aging ...estimation methods for swordfish (Xiphias gladius). We compared age estimates obtained from fin‐ray sections, otolith sections, whole otoliths, and vertebrae collected from 87 swordfish off the east coast of Corsica. Age estimates from otolith sections were most consistently estimated across different readers (lowest average percentage error), followed by fin‐ray sections, third vertebrae, and whole otoliths. When the age estimates from the otolith sections were compared with the other three age sclerochronological methods, we found the average percentage error to be lowest between the otolith section and fin‐ray methods. However, age estimates from fin rays proved most useful for estimating swordfish younger than 6 years, as the fin ray‐based age diverged from that of the otolith sections as the swordfish aged. Combining fin ray and otolith section techniques, we estimated the growth parameters of 1–12‐year‐old females (L∞ = 259.412, k = 0.113, t0 = −2.499) and 1–7‐year‐old males (L∞ = 175.543, k = 0.202, t0 = −2.239). We found that females grew significantly faster than males after 3 years and remained larger thereafter. Our calculated growth rates for this region of the north‐western Mediterranean Sea were lower than those of the Atlantic, Pacific, and eastern Mediterranean Sea swordfish populations, and similar to growth rates recorded for the western Mediterranean Sea populations. Our study provides critical knowledge on biological‐related parameters to serve as a guide for preserving the swordfish population in the Mediterranean Sea.
The Barcelona Convention (BC) aims at biodiversity conservation in the Mediterranean Sea, including in its Annex II a list of threatened species that need protection. This study aimed to assess ...existing scientific effort and knowledge on the invertebrate species of BC Annex II, through a systematic literature review. For the 52 invertebrates of Annex II, 1285 relevant articles were included in the review. Georeferenced records were retrieved from 183 additional articles and online databases (GBIF and WoRMS). For thirty species, <10 articles were retrieved; three species were not included in any study. The dominant research topic in the literature was ‘physiology/growth’ (22.5 %), followed by ‘ecology’ (20.1 %) and ‘distribution/habitat’ (17.1 %); only 6.6 % of the studies focused on ‘population assessment’. Research focus substantially varied by phylum and species. Fisheries were the main threat reported, followed by natural impacts, pollution, climate change, and coastal development. An evident lack of records from the southern Mediterranean coastline was attributed to the low research effort. Population trends were reported for only 23 species. A declining trend was commonly reported (148 cases), with only three studies reporting an increase and another three reporting stable populations. The critically endangered bivalve Pinna nobilis was the species with the most records of declining populations. No conservation action was proposed for most (31) BC Annex II species. Our analyses further revealed significant coverage gaps in several species within the current marine protected areas. Despite increasing regional collaboration, most of the BC Annex II invertebrate species are understudied, with knowledge gaps compromising conservation efforts.
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•Knowledge gaps compromise conservation efforts in the Mediterranean Sea.•Literature was systematically reviewed for 52 protected invertebrates.•For most species information was scarce with no population assessments.•For species assessed, a declining population trend was most commonly reported.•Fisheries, natural impacts, pollution and climate change were top-ranking threats.
To study the spatial distribution of sea surface plastics in marine protected and non-protected areas, 65 sea surface trawls were carried out using a Hydro-bios manta net coupled with a 335-μm mesh. ...A total of 19 sampling sites along the coastal waters of Mallorca, the “Parque Nacional Marítimo-Terrestre del Archipiélago de Cabrera” and Menorca in the Balearic Islands as well as along coastal waters of The Natural Park of Columbretes Islands (NW Mediterranean Sea) were sampled.
A total of 10,637 plastic items were identified and a subset of these items was categorized by shape, color, size and polymer composition. Plastic particles were found at each sampling site and in all samples. No microscale nor mesoscale variability in floating marine plastics abundance (particles/m2) was encountered throughout the study area where similar values were found in protected areas with no local land-based contamination sources, such as Columbretes 0.04 (±0.03) particles/m2, and in high anthropized areas, such as the island of Mallorca 0.04 (±0.07) particles/m2. However, differences were found in characteristics of plastic items (shape, polymer, and size range), with the protected area of Columbretes characterized by the presence of the highest density of very small plastic items composed mainly of fragments (93%). Quantified plastics from the marine environment were composed mainly of polyethylene (PE, 63.3%), polypropylene (PP; 24.9%), polycarbonate (PC; 4.6%) and polystyrene (PS, 3.3%). The polymer composition showed a homogenous composition between islands and differences were detected only amongst Columbretes and the other islands.
Results from this study provide further evidence of the ubiquity of plastics in the marine environment and highlight that remote and protected areas, such as Columbretes, are not exempt from plastic pollution, but receptor areas for small and aged floating plastics composed mainly by fragments, which might have potentially harmful effects on protected ecosystems.
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•All surface samples of near-shore surveys had plastic particles.•The proximity of sampled area and contamination sources do not influence plastic density.•Higher density of fragments and lower of films in protected than unprotected areas.•Less variability in polymer composition in protected than unprotected areas.•Plastic items smaller than 163,000 μm were detected only in protected areas.
Due to the increasing mass mortality of Pinna nobilis, mainly caused by the protozoan Haplosporidium pinnae along the Mediterranean Sea, it is necessary to develop rapid and effective methods to ...detect the pathogen. The present study describes the development and validation of a species-specific assay based on hydrolysis probe chemistry to detect H. pinnae DNA from faeces and pseudofaeces of P. nobilis. During a study campaign in the Gulf of Trieste (Italy) in the spring and summer of 2022, 18 samples (10 faeces and 8 pseudofaeces) were collected. DNA was isolated from all samples and the presence of H. pinnae was tested by amplifying a small portion of 18S rDNA using qPCR. The newly developed assay detected positive H. pinnae in the faeces of the fan mussel in the spring, while no evidence of an outbreak of H. pinnae was found in the summer. In addition, the method proved to be noninvasive and can be used to monitor suspected H. pinnae infections in the early stages when bivalves are still vital. Furthermore, fecal analysis allows the monitoring of P. nobilis without dissecting tissues. The presented assay can also be used to routinely monitor the progress of mass mortalities caused by H. pinnae and to screen for the pathogen in live fan mussels and other environmental matrices, such as water, sediment, and faeces from other species that can host the protozoan.
•Zooplankton and suprabenthos showed different taxonomical diversity between canyons.•Trophic niche of suprabenthos was wider than that of zooplankton.•Suprabenthos biomass and abundance did not ...follow the same trend in the two canyons.•Zooplankton biomass and abundance decrease with increasing distance from the coast.•Food availability, revealed by Chla, drives patterns of species abundance.
Submarine canyons act as hotspots of biodiversity, hosting vulnerable marine ecosystems, and playing a fundamental role in bridging coastal zones with deeper areas. Here, we investigated the suprabenthic and Deep Scattering Layer (DSL) zooplankton fauna, that play a key role in deep-sea food webs, as main resources for both mobile and sessile megafauna, in two submarine canyons (Squillace and Amendolara) of the Ionian Sea (Central Mediterranean Sea). Our results highlighted different taxonomic and functional diversity between the two adjacent canyons: (i) biomass and abundance of suprabenthos followed an opposite trend in the two canyons, increasing both with depth in Amendolara (higher abundance and biomass in the lower part of the canyon), and decreasing with depth in Squillace (greater in the head of the canyon); (ii) DSL zooplankton abundance and biomass followed a spatial distribution, decreasing with increasing distance from the coast for both canyons (i.e. lower offshore than at the head of the canyon). Food-web structure investigated by means of stable isotope analysis of δ13C and δ15N showed a more diverse trophic niche for suprabenthos than for zooplankton. Furthermore, possible feeding modes of species with unknown feeding behaviour have been proposed. The results of the current article highlight the different ecological processes occurring within each canyon. Understanding the spatial variations of communities inhabiting submarine canyons, especially those at the base of deep-sea food webs which can act as driver of megafaunal communities (both sessile and mobile-commercial species), is essential to focalise future conservation efforts.
The Mediterranean Sea has been described as one of the most affected areas by marine litter in the world. Although effects on organisms from marine plastic litter ingestion have been investigated in ...several oceanic areas, there is still a lack of information from the Mediterranean Sea. The main objectives of this paper are to review current knowledge on the impact of marine litter on Mediterranean biodiversity, to define selection criteria for choosing marine organisms suitable for use as bioindicator species, and to propose a methodological approach to assessing the harm related to marine litter ingestion in several Mediterranean habitats and sub-regions. A new integrated monitoring tool that would provide the information necessary to design and implement future mitigation actions in the Mediterranean basin is proposed.
According to bibliographic research and statistical analysis on current knowledge of marine litter ingestion, the area of the Mediterranean most studied, in terms of number of species and papers in the Mediterranean Sea is the western sub-area as well as demersal (32.9%) and pelagic (27.7%) amongst habitats.
Applying ecological and biological criteria to the most threatened species obtained by statistical analysis, bioindicator species for different habitats and monitoring scale were selected. A threefold approach, simultaneously measuring the presence and effects of plastic, can provide the actual harm and sub-lethal effects to organisms caused by marine litter ingestion. The research revealed gaps in knowledge, and this paper suggests measures to close the gap. This and the selection of appropriate bioindicator species would represent a step forward for marine litter risk assessment, and the implementation of future actions and mitigation measures for specific Mediterranean areas, habitats and species affected by marine litter ingestion.
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•Marine litter ingestion represents a serious harm to Mediterranean biodiversity.•A bibliographic research and statistics identified the most affected habitat/species by marine litter ingestion in the Med.•The identification of suitable bioindicators is necessary to address the effects of marine litter on marine fauna and habitat.•To assess the harm by marine litter ingestion is necessary to quantify its presence and ecotoxicological effects.
Selection of suitable bioindicators of marine litter ingestion and the simultaneous quantification of its presence and ecotoxicological effects is recommended in order to monitor the impact on Mediterranean fauna and habitats.
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