Patterns of trace metal bioaccumulation and trophic transfer in a phytoplankton-zooplankton-small pelagic fish marine food web

Zooplankton-based adverse outcome pathways: A tool for assessing endocrine disrupting compounds in aquatic environments

Endocrine disrupting compounds (EDCs) pose a significant ecological risk, particularly in aquatic ecosystems. EDCs have become a focal point in ecotoxicology, and their identification and regulation have become a priority. Zooplankton have gained global recognition as bioindicators, benefiting from rigorous standardization and regulatory validation processes. This review aims to provide a comprehensive summary of zooplankton-based adverse outcome pathways (AOPs) with a focus on EDCs as toxicants and the utilisation of freshwater zooplankton as bioindicators in ecotoxicological assessments. This review presents case studies in which zooplankton have been used in the development of AOPs, emphasizing the identification of molecular initiating events (MIEs) and key events (KEs) specific to zooplankton exposed to EDCs. Zooplankton-based AOPs may become an important resource for understanding the intricate processes by which EDCs impair the endocrine system. Furthermore, the data sources, experimental approaches, advantages, and challenges associated with zooplankton-based AOPs are discussed. Zooplankton-based AOPs framework can provide vital tools for consolidating toxicological knowledge into a structured toxicity pathway of EDCs, offering a transformative platform for facilitating enhanced risk assessment and chemical regulation.

Colonization, diversity, and seasonality of fishes at pelagic fish aggregating devices

The pelagic zone of the ocean can be a challenging environment in which to conduct research and as a result we lack the robust baseline abundance and diversity data, compared to what is available in more accessible coastal habitats, to be able to track changes or stressors to the biota in this environment. Many large-scale fisheries target pelagic fish, and much of the information available on these species is based on fisheries-dependent data that may be biased towards hotspots and commercially valuable fishes. Here, a long-term video and visual fish survey was conducted on two subsurface moored fish aggregating devices (FADs) in the pelagic waters of the central Bahamas to determine the feasibility of using moored pelagic FADs as tools for collecting fish abundance and diversity data. A wide range of species was documented, including large migratory fish that are the focus of commercial and recreational fisheries, and smaller often overlooked species on which little abundance or seasonality information exists. We found that FADs colonize quickly and reach a peak stable (albeit seasonally cyclical) abundance and diversity within the first several months after deployment. Species richness was higher in video surveys, but abundance was higher in visual surveys, except for sharks. Our results highlight the need to tailor survey methods to fit the context and study objective, and provide further evidence for the importance of fisheries-independent data in monitoring pelagic species.

The use of copper as plant protection product contributes to environmental contamination and resulting impacts on terrestrial and aquatic biodiversity and ecosystem functions

Copper-based plant protection products (PPPs) are widely used in both conventional and organic farming, and to a lesser extent for non-agricultural maintenance of gardens, greenspaces, and infrastructures. The use of copper PPPs adds to environmental contamination by this trace element. This paper aims to review the contribution of these PPPs to the contamination of soils and waters by copper in the context of France (which can be extrapolated to most of the European countries), and the resulting impacts on terrestrial and aquatic biodiversity, as well as on ecosystem functions. It was produced in the framework of a collective scientific assessment on the impacts of PPPs on biodiversity and ecosystem services in France. Current science shows that copper, which persists in soils, can partially transfer to adjacent aquatic environments (surface water and sediment) and ultimately to the marine environment. This widespread contamination impacts biodiversity and ecosystem functions, chiefly through its effects on phototrophic and heterotrophic microbial communities, and terrestrial and aquatic invertebrates. Its effects on other biological groups and biotic interactions remain relatively under-documented.

Assessment of Essential and Potentially Toxic Elements in Water and Sediment and the Tissues of Sciaena deliciosa (Tschudi, 1846) from the Coast of Callao Bay, Peru

The lorna drum Sciaena deliciosa is a coastal demersal species and one of the underlying artisanal fisheries in some areas of Peru, and is also a source of protein for Peruvian coastal dwellers. The investigation addresses concern about the environmental impact on this fish species and the potential risks to human health through the consumption of contaminated seafood. This research endeavors to assess the concentration of potentially toxic and essential elements in the muscle and liver tissues of S. deliciosa, in addition to the presence thereof in water and sediment capture areas on the coast of Callao, Peru. The study revealed that, in water samples, Ag, Ni, and Zn exceed Peruvian standards, but were below international standards, and Ba, P, Se, and Sn exceed international standards. In the sediments, As, Cd, Pb, Fe, and Zn were above international standards. In the fish, S. delicious muscle demonstrated As, Hg, and Pb exceeding at least one international standard. In the liver, As, Hg, Pb, and Cu exceed international standards. The study approach increased accuracy in risk assessments, offering crucial insights into the interplay between heavy metal pollution, water quality, and animal health, informing risk management strategies. Future studies can explore the long-term effects of heavy metal exposure on different organisms and consider their cumulative impact on health.

Linking seasonal plankton succession and cellular trace metal dynamics in marine assemblages

Factors affecting trace metal dynamics in marine plankton still need to be fully understood. Underlying mechanisms affecting cellular metal distribution, seasonal changes, and the influence of plankton community structure are poorly explored. This study comprehensively analyzed the seasonal changes in environmental factors, plankton community structure, and their impact on plankton cellular metal dynamics. Plankton samples were isolated, and trace metals (Cr, Mn, Fe, Co, Ni, Cu, As, Cd, Hg, and Pb) were analyzed with an inductively coupled plasma mass spectrometer (ICP-MS). Plankton community structure significantly changed with seasons (p < 0.05), which were mainly driven by temperature (seasonal change) and nutrients (eutrophication). Mean plankton cellular trace metals did not significantly change (p > 0.05) in the study area but were higher along estuaries likely due to differences in metal influx from rivers. However, their distribution patterns significantly differ between the wet and dry seasons, likely influenced by the changes in community structure and anthropogenic influx. Cellular trace metals, particularly in phytoplankton, strongly correlated with selected species suggesting the impacts of community structure in trace metal distribution. Hence, the influence of environmental factors in driving plankton succession may have caused a ripple effect on cellular trace metal distribution, especially in phytoplankton. However, both blooming species Skeletonema and Chaetoceros (diatoms) showed a contrasting relationship with cellular metals, suggesting the cooccurrence of bioaccumulation or biodilution mechanisms. This study shows the potential influence of community structure in cellular trace metal dynamics for marine plankton assemblages. However, more than plankton abundance and functional diversity, i.e., species diversity, might be needed to assess the community-level impacts on cellular metals.

Vanishing lead in the Loire River estuary: An example of successful environmental regulation

The behavior, and history of lead (Pb) contamination in the ecosystem of the Loire estuary was examined using elemental concentrations and Pb isotope data in water, sediment, bivalves, shrimps, and fish. In the estuary and in the surrounding coastal area, Pb concentrations in water and sediment decreased compared to concentrations determined in the 1980s, with concentrations ranging from 15.8 to 65.7 mg kg-1 in the surface sediment, 0.04-0.26 nM in the water column, and 48.0-77.9 mg kg-1 in suspended particles. Pb biomonitoring using blue mussels collected by the French Mussel Watch Program over the last 40 years showed a concentration decrease from 3.8 to 0.8 mg kg-1. A similar trend is observed in an estuarine sediment core. Changes in accompanying Pb isotope compositions strongly suggest a binary mixing process between Pb derived from terrigenous material and anthropogenic sources. Thus, environmental regulations restricting the release of lead into the environment contribute to a decrease in estuarine levels of this pollutant, which occurs on a decadal time scale.

What do small cetaceans tell us about trace elements pollution on the Argentinean coast? Franciscana dolphin as a biomonitor

Trace elements (TEs) constitute the oldest emerging pollutants globally, most occur from natural sources, but a few are derived from anthropogenic sources. Marine mammals are considered bioindicators of ecosystem contamination. The aims of this review is compile reports on essential and nonessential TEs occurrence in small cetaceans from Argentinean waters; and to review the existing information on the concentration of TEs in the Franciscana dolphin, a biomonitor species of the Argentine coastal marine ecosystem. We searched reports where levels of TEs were present in small cetaceans from and eight species were analysed: Pontoporia blainvillei, Tursiops truncatus gephyreus, Kogia breviceps, Delphinus delphis, Lagenorhynchus obscurus, Lagenodelphis hasei, Cephaloryhchus commersonii and Ziphius cavirostris. Essential TEs like Zn, Cu, Mn, Cr, Fe, Co, Ni, Mo, Se, As, Au, Ag, Sn, and nonessential TE as Pb, Cd, Hg, As was considered. The reports compiled in this article analysed kidney, liver, muscle and occasionally brain, skin, lung and spleen, covering a temporal range of 30 years, from 1982 to 2016. Of data analysis, we identify knowledge gaps, species of small cetaceans for which the concentration of trace metals is not yet known and areas on the Argentine coast where there are no reports that analyse them. The most recent information corresponds to the 2010 decade, and in those subsequent publications, the samples were taken at that time. This emphasizes the importance of reviewing this data, in order to compare old and new datasets, create contamination timelines and evaluate possible increases or decreases of contaminants in different study areas. The information recopilated will serve as valuable baselines to detect the future impact of increasing human, even natural, activities on marine ecosystems in the South Atlantic Ocean.

Metal/metalloid bioconcentration dynamics in fish and the risk to human health due to water contamination with atmospheric particulate matter from a metallurgical industrial area

Settleable atmospheric particulate matter (SeAPM) containing a mixture of metals, including metallic nanoparticles, has increased throughout the world, and caused environmental and biota contamination. The metal bioconcentration pattern in Nile tilapia (Oreochromis niloticus) was evaluated during a 30-day exposure to 1 g L-1 SeAPM and assessed the human health risk from consuming fish fillets (muscle) based on the estimated daily intake (EDI). SeAPM was collected surrounding an iron ore processing and steel industrial complex in Vitória city (Espírito Santo, Brazil) area. Water samples were collected daily for physicochemical analyses, and every 3 days for multi-elemental analyses. Metal bioconcentrations were determined in the viscera and fillet of fish every 3 days. The elements B, Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Rb, Sr, Ag, Cd, Pb, Hg, Ba, Bi, W, Ti, Zr, Y, La, Nb, and Ce were analyzed in SeAPM, water, and fish using inductively coupled plasma mass spectrometry. The metal concentration in SeAPM-contaminated water was higher than in control water. Most metals bioconcentrated preferentially in the fish viscera, except for the Hg and Rb, which bioconcentrated mostly in the fillet. The bioconcentration pattern was Fe > Al > Mn > Pb > V > La > Ce > Y > Ni > Se > As > W > Bi in the viscera; it was higher than the controls throughout the 30-day exposure. Ti, Zr, Nb, Rb, Cd, Hg, B, and Cr showed different bioconcentration patterns. The Zn, Cu, Sr, Sn, Ag, and Ta did not differ from controls. The differences in metal bioconcentration were attributed to diverse metal bioavailability in water and the dissimilar ways fish can cope with each metal, including inefficient excretion mechanisms. The EDI calculation indicated that the consumption of the studied fish is not safe for children, because the concentrations of As, La, Zr, and Hg exceed the World Health Organization's acceptable daily intake for these elements.

Distribution, bioaccumulation, and trace element transfer among trophic levels in the southeastern Gulf of California

Our understanding of the trophic transfer of pollutants in marine subtropical ecosystems remains limited due to the complexity of their food webs. Thus, we aimed to evaluate Cd, Cu, Mn, Pb, and Zn sources, incorporation, and trophodynamics throughout the food web of the southeastern Gulf of California by stomach content analysis, stable isotope analysis, isotope mixing models, and trace element analysis in biological and environmental matrices. The food web comprised three main trophic guilds (TG1, TG2, and TG3). The bioaccumulation of Cd and Zn from seawater was efficient (> 1000) in TG2 and TG3. Bioaccumulation factor from sediment (BSAF >1) evidenced of Cd in all trophic guilds. In addition, non-trophic Cd relationships were identified in the food web. Based on the trophic magnification factor (TMF), Mn and Pb showed biodilution (TMFMn = 0.38; TMFPb = 0.16), while Cu and Zn exhibited biomagnification (TMFCu = 2.08; TMFZn = 3.31).

Bioconcentration, bioaccumulation and biomagnification of mercury in plankton of the Mediterranean Sea

Plankton plays a prominent role in the bioaccumulation of mercury (Hg). The MERITE-HIPPOCAMPE campaign was carried out in spring 2019 along a north-south transect including coastal and offshore areas of the Mediterranean Sea. Sampling of sea water and plankton by pumping and nets was carried out in the chlorophyll maximum layer. Two size-fractions of phytoplankton (0.7-2.7 and 2.7-20 μm) and five of zooplankton (between 60 and >2000 μm) were separated, and their total mercury (THg) and monomethylmercury (MMHg) contents were measured. Bioconcentration of THg was significantly higher in the smallest phytoplankton size-fraction dominated by Synechococcus spp. The bioaccumulation and biomagnification of MMHg in zooplankton was influenced by size, food sources, biochemical composition and trophic level. MMHg was biomagnified in the plankton food web, while THg decreased toward higher trophic levels. Higher MMHg concentrations were measured in oligotrophic areas. Plankton communities in the Southern Mediterranean Sea had lower MMHg concentrations than those in the Northern Mediterranean Sea. These results highlighted the influence of environmental conditions and trophodynamics on the transfer of Hg in Mediterranean plankton food webs, with implications for higher trophic level consumers.

Metal and metallothionein concentrations in mesozooplankton from an oligotrophic offshore area in the eastern Mediterranean Sea (Cretan Passage/Levantine Sea)

Spatial variability of Cd, Cu, Cr, Ni, Zn, Fe, Mn, Pb and metallothionein (MT) concentrations were determined in mesozooplankton samples along the west-east axis of the Cretan Passage in the western Levantine Sea (Eastern Mediterranean). Metal and MT values from the present study are proposed as background levels, due to the lack of substantial anthropogenic activities in the area, where only maritime traffic and atmospheric deposition could be potential sources. Higher concentrations, of both metals and MTs, were recorded mainly at the western stations indicating higher metal bioavailability than in the eastern part. An inverse relationship of the metal zooplankton levels with zooplankton biomass, abundance and vital rates (production, respiration and ingestion rates), as well as salinity, was evident. We discuss the hypothesis that physical and biological characteristics of the marine environment, affecting growth dynamics of phytoplankton and zooplankton communities, may also act on metal uptake in oligotrophic marine systems.

Hydrocarbons in size-fractionated plankton of the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)

Aliphatic and polycyclic aromatic hydrocarbons (AHs and PAHs, respectively) were analyzed in the dissolved fraction (<0.7 μm) of surface water and in various particulate/planktonic size fractions (0.7-60, 60-200, 200-500 and 500-1000 μm) collected at the deep chlorophyll maximum, along a North-South transect in the Mediterranean Sea in spring 2019 (MERITE-HIPPOCAMPE campaign). Suspended particulate matter, biomass, total chlorophyll a, particulate organic carbon, C and N isotopic ratios, and lipid biomarkers were also determined to help characterizing the size-fractionated plankton and highlight the potential link with the content in AHs and PAHs in these size fractions. Ʃ28AH concentrations ranged 18-489 ng L-1 for water, 3.9-72 μg g-1 dry weight (dw) for the size fraction 0.7-60 μm, and 3.4-55 μg g-1 dw for the fractions 60-200, 200-500 and 500-1000 μm. AH molecular profiles revealed that they were mainly of biogenic origin. Ʃ14PAH concentrations were 0.9-16 ng L-1 for water, and Ʃ27PAH concentrations were 53-220 ng g-1 dw for the fraction 0.7-60 μm and 35-255 ng g-1 dw for the three higher fractions, phenanthrene being the most abundant compound in planktonic compartment. Two processes were evidenced concerning the PAH patterns, the bioreduction, i.e., the decrease in concentrations from the small size fractions (0.7-60 and 60-200 μm) to the higher ones (200-500 μm and 500-1000 μm), and the biodilution, i.e., the decrease in concentrations in plankton at higher suspended matter or biomass, especially for the 0.7-60 and 60-200-μm size fractions. We estimated the biological pump fluxes of Ʃ27PAHs below 100-m depth in the Western Mediterranean Sea at 15 ± 10 ng m-2 day-1, which is comparable to those previously reported in the South Pacific and Indian Ocean.

Concentration of mercury and other metals in an Arctic planktonic food web under a climate warming scenario

Arctic marine ecosystems act as a global sink of mercury (Hg) and other metals, and high concentrations of these have been measured in higher trophic-level organisms. Nevertheless, the concentrations of metals at the basis of the marine food web in the Arctic is less known despite the likelihood of biomagnification from dietary sources. We investigated the concentrations of mercury (Hg) and other metals in different size fractions of plankton in West Greenland. All size fractions contained detectable levels of Hg (ranging from 4.8 to 241.3 ng g dw-1) at all stations, although with high geographic variability, likely reflecting the sources of mercury (e.g., meltwater). In many cases, the concentrations in the larger-size fractions were lower than in the smaller-size fractions, suggesting depuration through the metabolic activity of mesozooplankton. Concentrations of Cd, Pb, V, Ni, and Cr were higher than previously reported elsewhere in the Arctic.

Zooplankton biomass, size structure, and associated metabolic fluxes with focus on its roles at the chlorophyll maximum layer during the plankton-contaminant MERITE-HIPPOCAMPE cruise

Recent studies have demonstrated that plankton can be a key pathway for the uptake and transfer of contaminants entering the marine environment up to top predators. The plankton-contaminant MERITE-HIPPOCAMPE cruise was devoted to quantifying contaminants in water and the whole plankton size range (10 size fractions) at 10 stations along a north-south transect in the western Mediterranean Sea from the French to the Tunisian coasts through the Provençal and Algerian basins. Pumping and filtering devices and net sampling have been used for collecting very high amounts of small particles and planktonic organisms in the chlorophyll maximum layer (CML). The present paper characterizes the zooplankton components for which the contaminant measurements were carried out. At each station, a horizontal towed Hydro-Bios net with a 60 μm mesh-size net was used to discriminate 5 size-fractions from 60 μm to a few mm. For each size-fraction, one part of the sample was used for dry weight measurements and the other one for estimating the contribution to biomass of detritus, phytoplankton, and among zooplankton of the major taxonomic groups based on the imagery tools ZOOSCAN and FLOWCAM. In each zooplankton size fraction, metabolic rates were calculated from the size spectrum to estimate trophic and excretion fluxes flowing through this fraction. These observations were compared to a similar analysis of tows in the upper layer (vertical) and the surface layer (horizontal). The total sampled biomass concentration at the CML was higher than in the water column (COL) and much higher than at the surface (SURF) in most of the stations, but in the CML and COL a substantial contribution was due to detritus mostly concentrated in the smallest size-fractions (60-200 μm and 200-500 μm). Absolute values of zooplankton biomass show neither a clear spatial pattern nor a significant difference between strata. The CML layer was dominated by copepods similarly to COL and SURF, but presented a higher contribution of nauplii and a near absence of appendicularians. At some stations, crustaceans and gelatinous plankton could be important contributors to CML. The zooplankton biomass composition of the two smallest fractions (<500 μm) was dominated by nauplii, small copepods and, occasionally, by small miscellaneous organisms (mostly pteropodes). In contrast, clear differences between stations appeared for the largest fractions (>500 μm) due to large crustaceans, gelatinous organisms, and chaetognaths. These changes in biomass composition according to size fractions suggest a progressive trophic shift from dominant herbivory in the smallest fractions to more contrasted trophic structure (including carnivory) in the largest fractions. The daily carbon demand and the N and P excretion of zooplankton were on average higher at the CML but with no significant difference with COL. The zooplankton grazing represented 2.7 to 22.7 % of the phytoplankton stock per day, whereas its excretion represented a daily N and P recycling compared to dissolved inorganic nitrogen and phosphorus stocks ranging respectively from 0.2 to 19 % and from 0 to 21 %. This information should help in the interpretation of the content of various contaminants in zooplankton fractions.

Experimental determination of concentration factors of Mn, Zn and I in the phytoplankton species Phaeodactylum Tricornutum

Anthropogenic radionuclides released into the environment cause a radiation dose to wildlife and humans which must be quantified, both to assess the effect of normal releases, and to predict the consequences of a larger, unplanned release. To estimate the spread of the radioactive elements, the ecosystem around release points is modelled, and element uptake is usually quantified by concentration factors (CF), which relates the concentration of an element in an organism to the concentration of the same element in a medium under equilibrium conditions. In this work, we experimentally determine some phytoplankton CF that are needed for improved modelling of the marine ecosystems around nuclear facilities and release points. CFs that require better determination have been identified through literature search. Sensitivity studies, using the currently used ecosystem modelling software PREDO, show that for most studied groups, the dose committed by the respective radionuclides is almost proportional to the corresponding phytoplankton CFs. In the present work, CFs are determined through laboratory experiments with cultured phytoplankton and radionuclides of the concerned elements, assessing the element uptake by the phytoplankton through detection of the emitted radiation. The three CF assessed in this work were those for manganese, zinc and iodine in phytoplankton. Conservative estimates of these CF based on the present data are 40 000 L/kg for manganese, 50 000 L/kg for zinc and 180 L/kg for iodine with the phytoplankton masses referring to their dry weight.

Contamination of planktonic food webs in the Mediterranean Sea: Setting the frame for the MERITE-HIPPOCAMPE oceanographic cruise (spring 2019)

This paper looks at experiential feedback and the technical and scientific challenges tied to the MERITE-HIPPOCAMPE cruise that took place in the Mediterranean Sea in spring 2019. This cruise proposes an innovative approach to investigate the accumulation and transfer of inorganic and organic contaminants within the planktonic food webs. We present detailed information on how the cruise worked, including 1) the cruise track and sampling stations, 2) the overall strategy, based mainly on the collection of plankton, suspended particles and water at the deep chlorophyll maximum, and the separation of these particles and planktonic organisms into various size fractions, as well as the collection of atmospheric deposition, 3) the operations performed and material used at each station, and 4) the sequence of operations and main parameters analysed. The paper also provides the main environmental conditions that were prevailing during the campaign. Lastly, we present the types of articles produced based on work completed by the cruise that are part of this special issue.

Spatial variations of biochemical content and stable isotope ratios of size-fractionated plankton in the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)

Plankton represents the main source of carbon in marine ecosystems and is consequently an important gateway for contaminants into the marine food webs. During the MERITE- HIPPOCAMPE campaign in the Mediterranean Sea (April-May 2019), plankton was sampled from pumping and net tows at 10 stations from the French coast to the Gulf of Gabès (Tunisia) to obtain different size fractions in contrasted regions. This study combines various approaches, including biochemical analyses, analyses of stable isotope ratios (δ¹³C, δ¹⁵N), cytometry analyses and mixing models (MixSiar) on size-fractions of phyto- and zooplankton from 0.7 to >2000 μm. Pico- and nanoplankton represented a large energetic resource at the base of pelagic food webs. Proteins, lipids, and stable isotope ratios increased with size in zooplankton and were higher than in phytoplankton. Stable isotope ratios suggest different sources of carbon and nutrients at the base of the planktonic food webs depending on the coast and the offshore area. In addition, a link between productivity and trophic pathways was shown, with high trophic levels and low zooplankton biomass recorded in the offshore area. The results of our study highlight spatial variations of the trophic structure within the plankton size-fractions and will contribute to assess the role of the plankton as a biological pump of contaminants.

How plastic debris and associated chemicals impact the marine food web: A review

Contamination from plastic debris is omnipresent in marine environments, posing a substantial risk to marine organisms, food webs and the ecosystem. The overlap between the size range of marine plastic pollution with prey means that plastics are readily available for consumption by organisms at all trophic levels. Large plastic debris can directly result in the death of larger marine organisms, through entanglement, strangulation, choking and starvation through a false sense of satiation. Whereas smaller plastic debris, such as micro- and nano-plastics can have adverse impact to marine organisms due to their large surface area to volume ratio and their ability to translocate within an organism. Various physiological processes are reported to be impacted by these small contaminants, such as feeding behaviour, reproductive outputs, developmental anomalies, changes in gene expression, tissue inflammation and the inhibition of growth and development to both adults and their offspring. Micro- and nano-plastics are still relatively poorly understood and are considered a hidden threat. Plastic is a complex contaminant due to the diversity in sizes, shapes, polymer compositions, and chemical additives. These factors can each have unique and species-specific impacts. Consumption of plastics can occur directly, through ingestion and indirectly, through trophic transfer, entanglement of prey, adherence of plastics to external surfaces, and adherence of organisms to the external surfaces of plastics. This review investigated the intrusion of plastics into the marine food web and the subsequent consequences of plastic pollution to marine biota.The objective of this review was to identify the complexity of impacts to marine organisms through the food web from plastic contamination. Through a concise analysis of the available literature the review has shown that plastic pollution and their associated additives can adversely impact environmental and biological health.

Rare earth element uptake mechanisms in plankton in the Estuary and Gulf of St. Lawrence

The global shift toward green energy alternatives escalates demands for new resources, including rare earth elements (REEs), as per their implications in various green innovations. However, our understanding of their environmental cycle, especially the interactions with aquatic organisms, remains deficient, ultimately hindering environmental protection efforts. Here, we investigate the accumulation of REEs and 18 other elements in bulk and sorted plankton collected with different net mesh sizes (30, 63, 200, 333, 500 μm) in the Estuary and Gulf of St. Lawrence in the summer and winter of 2020. We observed significant correlations between the concentrations of REEs and elements of different charge numbers and ionic radii (Ba, Co, Cs, Fe, Mn, Pb, Rb and V), indicating non-selective uptake of REEs into plankton. All these elements have their highest concentrations in the fluvial corridor and upper estuary, with more significant enrichment in phytoplankton ([La] = 26.4 ± 4.8 mg kg^-1) than zooplankton ([La] = 11.6 ± 8.3 mg kg^-1). Their concentrations decrease to the minimum in the Gulf of St. Lawrence, especially in zooplankton ([La] = 4.8 × 10^-2 ± 3.2 × 10^-2 mg kg^-1). We also assessed REE patterns to identify differential REE fractionation processes and anomalies. The freshwater plankton exhibits enrichment of middle REEs (MREEs) relative to the light and heavy REEs (LREEs and HREEs), potentially because of the higher binding affinity of MREEs on cellular surface transporters and metal loading effects. In estuarine and marine settings, the REE patterns in biological samples align with suspended particles, exhibiting a linear trend with LREE enrichment. This process is more noticeable in sorted macrozooplankton, which have significant Eu anomalies (Eu/Eu* up to 2), indicating differential incorporation of REEs into the chitin shells. This study highlights the significant enrichment of REEs into freshwater primary producers and the accumulation pathway similar to other inorganic elements.

To what extent are filter feeder elasmobranchs exposed to marine pollution? A systematic review

Filter feeding elasmobranchs may be considered as biological indicators of marine pollution, despite most of these species are under some degree of extinction risk. Among threats to this taxonomic group, marine pollution might represent an additional concern for their survival. In this review, a comprehensive systematic search of scientific literature on pollutants in filter feeding elasmobranchs was conducted to evaluate the bioaccumulation patterns, and risk for human consumers. We found that, despite an increasing trend in the number of published studies, the geographical coverage is still very limited and most of the studies focused solely on trace elements (70.8%). Among sharks, Rhincodon typus was the most represented species (66.7%), while Mobula mobular the most studied ray species (41.7%). Comparing the levels of pollutants in filter feeders between ocean basins, this review highlighted that Hg, As and Cd levels are mostly higher in those areas affected by both strong natural and anthropogenic source of emissions, such as the Indian Ocean. With regards to OCs, ΣPCB levels in muscle of C. maximus were between 4.3 and 50.5 μg kg^-1 ww, highlighting a persistent contamination of PCB in the Mediterranean Sea. Some species exceeded the maximum allowable limits for foodstuff consumption for As, Cd and Pb. A total of 77.8% of the analyzed species exceeded the Environmental Quality Standards for Hg, while they were always below the EQS_biota for HCB, PBDEs, PFOS and DDT. Given their feeding mechanism that continuously samples the marine environment, further investigations are urgently needed to determine not only the extent of contaminant exposure in different hotspot locations but also the risks posed to the elasmobranch health.

Distribution and accumulation of metals and metalloids in planktonic food webs of the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)

Particle-size classes (7 fractions from 0.8 to 2000 μm) were collected in the deep chlorophyll maximum along a Mediterranean transect including the northern coastal zone (bays of Toulon and Marseilles, France), the offshore zone (near the North Balearic Thermal Front), and the southern coastal zone (Gulf of Gabès, Tunisia). Concentrations of biotic metals and metalloids (As, Cd, Cr, Cu, Fe, Mn, Ni, Sb, V, Zn) bound to living or dead organisms and faecal pellets were assessed by phosphorus normalisation. Biotic metals and metalloids concentrations (except Cr, Mn, and V) were higher in the offshore zone than in the coastal zones. In addition, biotic Sb and V concentrations appeared to be affected by atmospheric deposition, and biotic Cr concentrations appeared to be affected by local anthropogenic inputs. Essential elements (Cd, Cu, Fe, Mn, Ni, V, Zn) were very likely controlled both by the metabolic activity of certain organisms (nanoeukaryotes, copepods) and trophic structure. In the northern coastal zone, biomagnification of essential elements was controlled by copepods activities. In the offshore zone, metals and metalloids were not biomagnified probably due to homeostasis regulatory processes in organisms. In the southern coastal zone, biomagnification of As, Cu, Cr, Sb could probably induce specific effects within the planktonic network.

Transport of trace metals and their bioaccumulation in zooplankton from Changjiang (Yangtze River) to the East China Sea

The present study conducted a comprehensive field investigation on the transport and bioaccumulation of six trace metals (Cr, Cd, Pb, Mn, Ni, Cu) along a transect from Changjiang (Yangtze River) to the East China Sea continental shelf, which exhibited large variations in physiochemical properties (salinity, turbidity, pH, chlorophyll a, total nitrogen, dissolved oxygen, dissolved and particulate organic matter). From riverine sites to marine sites, dissolved Cr and Cd significantly increased, dissolved Pb and Mn showed less variations, while dissolved Cu and Ni showed complex spatial distribution patterns. Particulate trace metals (for Cr, Mn, Ni and Cu) were significantly negatively correlated with salinity. As a result, partition coefficients of trace metals (except Pb) were all significantly negatively correlated with salinity, indicating high salinity facilitated desorption/dissolution of metals from particulate phase. Additionally, the Changjiang derived particulate Pb, Mn, Ni and Cu sharply decreased (particularly for Mn) at the downstream of turbidity maximum zone, suggesting the efficient trapping of metals within this region. We further investigated the site-specific bioaccumulation of trace metals in size-fractionated zooplankton. Metal contents in macro-zooplankton were lower than micro- and meso-zooplankton owing to size-dependent zooplankton communities, while site-specific metal bioaccumulation mainly driven by site-specific zooplankton communities and salinity. The bioaccumulation factors of metals (Cr, Cd, Ni and Cu) were significantly negatively correlated with salinity, indicating high salinity hampered metal uptake which might attribute to competition of cations and formation of less bioavailable inorganic complexes with anions. Overall, high salinity generated two-sided effects (elevated dissolved metal concentrations Vs. reduced metal bioaccumulation) on metal contents in zooplankton (especially for Cr, Cd, Ni, and Cu), resulting in metal- and site-specific metal contents. We noticed relatively higher metal contents in zooplankton at hypoxia sites which could further transfer to predators in the East China Sea, and the underlying mechanisms still require future investigation.

Isotopic compositions of copper and zinc in plankton from the Mediterranean Sea (MERITE-HIPPOCAMPE campaign): Tracing trophic transfer and geogenic inputs

This study uses Cu and Zn isotopic compositions as proxies of sources and metal transfers in the planktonic food webs from the Mediterranean Sea. Plankton was collected in spring 2019 in the deep chlorophyll maximum (DCM) along a North-South transect including coastal and offshore zones (MERITE-HIPPOCAMPE campaign). δ⁶⁵Cu and δ⁶⁶Zn were determined on four planktonic size fractions from 60 to 2000 μm. Combined δ⁶⁵Cu and δ⁶⁶Zn with geochemical tracers (Ti, particulate organic phosphorus) showed that geogenic particles were ubiquitous with plankton assemblages. The δ¹⁵N ecological tracer showed that planktonic food web was enriched in heavy isotopes of Cu and Zn in the higher trophic levels. δ⁶⁵Cu were correlated with picoplankton in the offshore zone, and with zooplankton in the southern coastal zone. Firmicutes bacteria were found correlated with δ⁶⁶Zn in northern and southern coastal zones suggesting decomposition of particulate matter at the DCM. These findings suggest that biogeochemical process may impact Cu and Zn isotopy in the planktonic community.

Non-proportional distribution and bioaccumulation of metals between phytoplankton and zooplankton in coastal waters

Metal concentrations were concurrently quantified in seawater, phytoplankton, and zooplankton from a heavily impacted coast of southern Taiwan. Combined size and density fractionation were used to accurately quantify metal concentrations in phytoplankton. Cr, Co, Ni, Cu, As, and Pb were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS). As expected, metals significantly increased with an order of seawater < phytoplankton < zooplankton (p < 0.05); but did not differ between estuarine, nearshore, and offshore sites (p > 0.05). Metals were higher along Kaohsiung Harbor and marine outfall diffusion sites, highlighting their major impacts on plankton metal contamination. Notably, phytoplankton (Cr BCF > 100; half of the sites) significantly accumulated more metals contrary to zooplankton (BAF < 10). Metal concentrations and bioaccumulation factors between phytoplankton and zooplankton showed significant negative correlations. This demonstrates a non-proportional distribution and bioaccumulation of metals in phytoplankton and zooplankton-corroborating laboratory findings on zooplankton ability to control metals, irrespective of significantly high bioaccumulation in phytoplankton.

Ultraphytoplankton community structure in subsurface waters along a North-South Mediterranean transect

Here we assessed the subsurface ultraphytoplanktonic (< 10 μm) community along a North-South round-trip Mediterranean transect as part of a MERITE-HIPPOCAMPE cruise campaign in April-May 2019. Temperature, salinity, and nutrient concentrations in subsurface waters (2-5 m depth) were also measured along the transect. The subsurface ultraphytoplankton community structure was resolved with a spatial resolution of few kilometers and temporal resolution of 30-min intervals using automated pulse shape recording flow cytometry. The subsurface waters were clustered into seven areas based on temperature and salinity characteristics. Synechococcus were by far the most abundant group in all prospected zones, and nanoeukaryotes were the main biomass component, representing up to 51 % of ultraphytoplanktonic carbon biomass. Apparent net primary productivity (NPP) followed a decreasing gradient along the transect from north to south and was mostly sustained by Synechococcus in all zones. These findings are likely to have implications in terms of the trophic transfer of contaminants in planktonic food webs, as they highlight the potential role of nanoplankton in contaminants bioaccumulation processes and the potential role of Synechococcus in a likely transfer via grazing activities.

Ecosystem based approach to delineate coastal degradation of Hawks bay, Karachi, Pakistan

Hawks Bay (HB) a renowned recreational beach, an important small scale fishery and nesting ground of an endangered turtle species encountering massive environmental degradation. Its eastern bay cover scattered mangrove patches and the western bay embraces sandy and rocky beach that terminus the area into great ecological and economic concerns. Here, we have figured out tendency of contamination entering in the ecosystem and elaborate food ∼ web dynamics around HB. An integrated approach was applied to evaluate level of contamination in water, sediments, planktons, seaweeds, mangrove leaves, crabs and fishes. In the sampled population phytoplankton were comprises of (39 Taxa), zooplankton (21), crab (1) and fishes (9) from pelagic demersal domains. The concentration of copper (Cu), iron (Fe), zinc (Zn), lead (Pb) and chromium (Cr) were detected using double-beam Atomic Absorption Spectrophotometer (AAS). The trophic transfer (TTF), contamination factor (CF), pollution load index (PLI), bioaccumulation factor (BAF) and accumulation factor (AF) were calculated round the year. The CF reveals that the area is moderately contaminated whereas PLI (>1) indicate that area is massively polluted by the industrial wastes. Multivariate approach of Principle Component Analysis was applied using pooled data of TTF that defines PC-I (41.56%) and PC- II (31.44%) variability among axes. Evaluation of metal contamination from micro to macro and from surface to bottom exhibits considerable load being received by HB ecosystem echoes stringent actions to curb further degradation of an important area.

New insights into trace metal speciation and interaction with phytoplankton in estuarine coastal waters

In coastal productive zones, phytoplankton activity may influence trace metal speciation and partitioning at short temporal scale. We coupled hourly in situ voltammetry quantification of the lead (Pb), cadmium (Cd), and copper (Cu) potentially bioavailable fractions, using an innovative submersible sensing probe (the TracMetal), to surface water sampling for the quantification of the targeted trace metals in the dissolved <0.2 μm and <0.02 μm fractions, suspended particles, and phytoplankton nets in the Gironde Estuary mouth. The in situ TracMetal monitoring reflected real-time dynamic Cd and Cu regeneration related to algal cells under post-bloom conditions as well as Pb remobilization due to photoreduction of colloids. The potentially bioavailable fraction consisted in 30, 30-50 and <10 % of the total dissolved fraction for Pb, Cd, and Cu, respectively, representing crucial ecotoxicological information. Metal bioconcentration factors using the dynamic fraction concentrations showed levels up to 10⁷ for Cu in phytoplankton.

Trace metal elements and organic contaminants are differently related to the growth and body condition of wild European sea bass juveniles

Chemical contaminants are one of the causes of the ongoing degradation of coastal and estuarine nurseries, key functional habitats in which the juveniles of many marine species grow. As chemical contaminants can cause a decrease in the energy available and induce defence mechanisms reducing the amount of energy allocated to life history traits, quantifying their effect on the fitness of juvenile fish is key to understand their population-level consequences. However, these effects are primarily estimated experimentally or in the wild but on a limited number of contaminants or congeners that do not reflect the wide variety of chemical contaminants to which juvenile fish are exposed. To address this issue, we measured concentrations of 14 trace metal elements (TMEs) and bioaccumulative organic contaminants (OCs) in European sea bass juveniles (1-year-old) from three major French nurseries (Seine, Loire and Gironde estuaries). We tested the hypotheses that (i) levels and profiles of contaminants differed among studied nurseries, and ii) fish growth and body condition (based on morphometric measurements and muscle C:N ratio) were lower in individuals with higher contaminant concentrations. Multivariate analyses showed that each nursery had distinct contaminant profiles for both TMEs and OCs, confirming the specific contamination of each estuary, and the large array of contaminants accumulated by sea bass juveniles. Increasing concentrations in some TMEs were associated to decreased growth, and TMEs were consistently related to lower fish body condition. The effect of OCs was more difficult to pinpoint possibly due to operational constraints (i.e., analyses on pooled fish) with contrasting results (i.e., higher growth and decreased body condition). Overall, this study shows that chemical contaminants are related to lower fish growth and body condition at an early life stage in the wild, an effect that can have major consequences if sustained in subsequent ages and associated with a decline in survival and/or reproductive success.

Trophic transfer of copper decreases the condition index in Crassostrea gigas spat in concomitance with a change in the microalgal fatty acid profile and enhanced oyster energy demand

Due to new usages and sources, copper (Cu) concentrations are increasing in the Arcachon Basin, an important shellfish production area in France. In the present paper, the trophic transfer of Cu was studied between a microalga, Tetraselmis suecica, and Crassostrea gigas (Pacific oyster) spat. An experimental approach was developed to assess Cu exposure, transfer and toxicity on both phytoplankton and spat. Exposure of microalgal cultures to Cu for 7-8 days (3.1 ± 0.1, 15.7 ± 0.2 and 50.4 ± 1.0 μg Cu·L^-1 for the control, Cu15 and Cu50 conditions, respectively) led to concentrations in microalgae (28.3 ± 0.9 and 110.7 ± 11.9 mg Cu·kg dry weight^-1 for Cu15 and Cu50, respectively) close to those measured in the field. Despite Cu accumulation, the physiology of the microalgae remained poorly affected. Exposed cultures could only be discriminated from controls by a higher relative content in intracellular reactive oxygen species, and a lower relative content in lipids together with a reduced metabolic activity. By contrast, the fatty acid profile of microalgae was modified, with a particularly relevant lower content of the essential polyunsaturated fatty acid 22:6n-3 (docosahexaenoic acid [DHA]). Following 21 days of spat feeding with Cu15 and Cu50 microalgal cultures, trophic transfer of Cu was observed with a high initial Cu concentration in spat tissues. No effect was observed on oxidative stress endpoints. Cu exposure was responsible for a decrease in the spat condition index, an outcome that could be related to an insufficient DHA supply and extra energy demand as suggested by the overexpression of genes involved in energy metabolism, ATP synthesis and glycogen catabolism.

Bioaccumulation of metals in the planktonic food web in the Gulf of Guinea

Metal contamination is a threat for marine ecosystems from an environmental, economic and public health perspective, particularly in regions where local communities rely on marine resources such as the Gulf of Guinea. Plankton are the point of entry for metals in the marine food web, potentially contaminating seafood. We investigated the bioaccumulation of 12 metals in three size classes of plankton from the coast of Ghana. Metal concentrations were high in the micro- and mesoplankton, in particular for Mn, Mo and Zn (up to 100 mg kg^-1) and Fe (>100 mg kg^-1). All metals significantly bioaccumulated (10³-10⁶ L kg^-1) and the bioaccumulation increased from the smallest to larger size fractions, suggesting a biomagnification. These metals included the highly toxic elements As, Cd and Pb. Our results highlight the need to monitor metal occurrence in the Gulf of Guinea, to reduce pollution and ensure food safety, in accordance with the UN SDG #14.

Assessment of trace metal concentrations in Indian Ocean silky sharks Carcharhinus falciformis and their toxicological concerns

This study assessed the concentrations of nine trace metals from juvenile C. falciformis caught from Indian Ocean. This study also discussed the metal pollution index (MPI) and bioconcentration factor (BCF) of each element, and their correlations. Further, the potential health risks of consuming shark muscles (THI) were evaluated. Results showed the mean concentrations of 9 elements as follows: Cu (0.36 ± 0.17), Zn (5.19 ± 16.6), Pb (0.12 ± 0.23), Cd (0.17 ± 0.21), Cr (0.57 ± 1.61), Ni (0.086 ± 0.51), As (1.36 ± 0.83), Co (0.000073 ± 0.0074), and V (0.0024 ± 0.0094) mg/kg ww. The BCF values of the elements were higher than 1, with Co and V being the lowest indicating their bioaccumulative behavior. Correlation analysis showed MPI to be highly correlated with Cu, indicating its greater contributions to the total pollution load. Principal components analysis explained 81.0% of the variability in biometric characteristics and metal concentrations. Health risk assessment for consuming shark muscle in Taiwanese male and female adults suggests potential chronic non-carcinogenic health hazards.

Mediterranean Mercury Assessment 2022: An Updated Budget, Health Consequences, and Research Perspectives

Mercury (Hg) and especially its methylated species (MeHg) are toxic chemicals that contaminate humans via the consumption of seafood. The most recent UNEP Global Mercury Assessment stressed that Mediterranean populations have higher Hg levels than people elsewhere in Europe. The present Critical Review updates current knowledge on the sources, biogeochemical cycling, and mass balance of Hg in the Mediterranean and identifies perspectives for future research especially in the context of global change. Concentrations of Hg in the Western Mediterranean average 0.86 ± 0.27 pmol L^-1 in the upper water layer and 1.02 ± 0.12 pmol L^-1 in intermediate and deep waters. In the Eastern Mediterranean, Hg measurements are in the same range but are too few to determine any consistent oceanographical pattern. The Mediterranean waters have a high methylation capacity, with MeHg representing up to 86% of the total Hg, and constitute a source of MeHg for the adjacent North Atlantic Ocean. The highest MeHg concentrations are associated with low oxygen water masses, suggesting a microbiological control on Hg methylation, consistent with the identification of hgcA-like genes in Mediterranean waters. MeHg concentrations are twice as high in the waters of the Western Basin compared to the ultra-oligotrophic Eastern Basin waters. This difference appears to be transferred through the food webs and the Hg content in predators to be ultimately controlled by MeHg concentrations of the waters of their foraging zones. Many Mediterranean top-predatory fish still exceed European Union regulatory Hg thresholds. This emphasizes the necessity of monitoring the exposure of Mediterranean populations, to formulate adequate mitigation strategies and recommendations, without advising against seafood consumption. This review also points out other insufficiencies of knowledge of Hg cycling in the Mediterranean Sea, including temporal variations in air-sea exchange, hydrothermal and cold seep inputs, point sources, submarine groundwater discharge, and exchanges between margins and the open sea. Future assessment of global change impacts under the Minamata Convention Hg policy requires long-term observations and dedicated high-resolution Earth System Models for the Mediterranean region.

Comparative trace metal assessment in phytoplankton using size and density fractionation

Trace metal assessment in marine phytoplankton is challenging due to complex assemblages and variable amounts of abiogenic suspended particulates. Using aliquots, this study were able to compare trace metal concentrations in plankton samples subjected to size and density fractionation. Elements including Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Hg, and Pb were analyzed by inductively coupled plasma mass spectrometer (ICP-MS). Trace metals were found to be significantly higher in size fractionated than density fractionated plankton for both small (1.2-50 μm) and large (50-120 μm) fractions. Metals from abiogenic sources (61-88%) also significantly contributed to trace metals detected in 1.2-120 μm suspended particulates collected from Kaohsiung Harbor. Results suggest that size fractionation can potentially overestimate trace metals in phytoplankton. It is therefore recommended combining the two methods by first isolating different size fractions followed by density fractionation to separate phytoplankton from zooplankton, and abiogenic particulates from phytoplankton assemblages, respectively.

Mercury concentrations, biomagnification and isotopic discrimination factors in two seabird species from the Humboldt Current ecosystem

Assessing mercury (Hg) biomagnification requires the description of prey-predator relationships, for each species and ecosystem, usually based on carbon and nitrogen isotope analyses. Here, we analyzed two seabirds from the Humboldt Current ecosystem, the Guanay cormorant (Phalacrocorax bougainvillii) and the Peruvian booby (Sula variegata), as well as their main prey, the Peruvian anchovy (Engraulis ringens). We reported Hg concentrations, Hg biomagnification (BMF) and isotopic discrimination factors (Δ¹³C and Δ¹⁵N) in seabird whole blood. BMFs and Δ¹³C in our study (on wild birds where diet was not controlled) were similar to other piscivorous seabirds previously studied in captive settings, but Δ¹⁵N were lower than most captive experiments. We observed lower Hg concentrations in Humboldt seabirds compared to other oligotrophic ecosystems, possibly due to Hg biodilution in the high biomass of the first trophic levels. This work calls for a better characterization of Hg trophic dynamics in productive upwelling ecosystems.

High inter-species variability in elemental composition of the twilight zone fauna varies implications for predators and exploitation by humans

While the importance of oceanic micronektonic species in biogeochemical cycles and in the transfer of matter in food webs is globally recognized, specific knowledge on elemental concentrations and their variability within this community is still poorly documented. Here, we report for the first time in the Bay of Biscay, North-East Atlantic, the body composition in various biological parameters and chemical elements of a meso-to bathypelagic micronektonic community. Stable carbon and nitrogen isotope compositions (δ¹³C, δ¹⁵N), C:N ratios, energy density, as well as the concentrations in 6 macro-minerals and 13 trace elements including essential (micro-nutrients) and non-essential elements (undesirables, with no know biological function) were measured in whole organisms of 4 crustacean and 11 fish species caught simultaneously around 800 m depth. The results showed a low variability of δ¹³C values, confirming that all studied species share the same habitat. On the contrary, large differences were observed among species for several elements. Trace elements showed the greatest variability (i.e. larger range of values), especially silver (Ag), arsenic (As), cadmium (Cd), cobalt and vanadium. Significant differences were also revealed among taxa for Ag, As, Cd, copper and strontium concentrations (with crustaceans > fish), as well as for δ¹⁵N values and phosphorus concentrations (with fish > crustaceans). Although concentrations varied greatly among species, they could be grouped according to their energy density and composition in 19 chemical elements, through hierarchical clustering analysis. Six functional groups of species have been thus identified, reflecting contrasted nutritional benefit and/or exposure to undesirables for predators feeding on this deep pelagic community. Finally, the concentrations measured for the potentially toxic trace elements (undesirables) exceeded the existing European thresholds for Cd and to a lesser extent mercury (Hg), which point out potential risks in the perspective of a future exploitation of these deep living resources by humans.

A study of trophic structure, physiological condition and mercury biomagnification in swordfish (Xiphias gladius): Evidence of unfavourable conditions for the swordfish population in the Western Mediterranean

Studies integrating trophic ecology, physiological condition and accumulation of heavy metals in top predators, such as swordfish, are needed to better understand the links between them and the risk to humans associated with consumption of these fish. This research focuses on the swordfish of the Catalan Sea and follows a multi method approach that considers their diet, their liver lipid content, and mercury accumulation in their bodies as well as in their prey. The aim is to highlight the links between trophic ecology, physiology (fish condition), and eco-toxicology. Results indicate that poor condition of swordfish based on size and the levels of lipid in the liver, and the high Hg levels accumulated to the trophic web (particularly from cephalopods) may indicate potential unfavourable feeding and reproduction conditions for swordfish in the NW Mediterranean and this warrants further investigation.

Distribution and environmental geochemical indices of mercury in tar contaminated beaches along the coast of Qatar

The current study aimed to gauge total mercury (THg) concentration and the environmental geochemical indices in tarmat contaminated sediments and test their presence in targeted coastal species. Layers of hard asphalt-like tarmats and sediment samples were collected from 34 sites along the coast of Qatar. The mean concentration of THg in tarmat-sediment mixture is 89 ± 20 ng·g^-1. THg concentration varies significantly between the northern and eastern coasts. Geographically, sampling area were divided into four zones according to the relative closeness with low to serious potential ecological risk index (E_r), moderate pollution load index (PLI), moderate Geoaccumulation index (I_geo), and no toxic risk (TRI) trending as Northern (Zones 4, 3) > North-Eastern (Zone 1) > Western (Zone 2) coasts. Three biota classes (Gastropoda, Bivalvia, and Crustacea) were sampled on the tarmat which the hermit crab (Clibanarius signatus) from Ras Rakan island obtained the highest THg (977 ng·g^-1) and BSAF (29.70).

"Non-traditional" stable isotopes applied to the study of trace metal contaminants in anthropized marine environments

The advent of Multicollector ICP-MS inaugurated the analysis of new metal isotope systems, the so-called "non-traditional" isotopes. They are now available tools to study geochemical and ecotoxicological aspects of marine metal contamination and hence, to push the frontiers of our knowledge. However, such applications are still in their infancy, and an accessible state-of-the-art describing main applications, obstacles, gaps, and directions for further development was missing from the literature. This paper fills this gap and aims to encourage the marine scientific community to explore the contributions of this newly available information for the fields of chemical risk assessment, biomonitoring, and trophic transfer of metal contaminants. In the current "Anthropocene" epoch, metal contamination will continue to threaten marine aquatic ecosystems, and "non-traditional" isotopes can be a valuable tool to detect human-induced changes across time-space involving metal contaminants, and their interaction with marine biota.

Assessment of potential variability of cadmium and copper trace metals using hindcast estimates

Trace metals are vital to primary productivity and play an essential role as main components in regulating oceanic biogeochemical cycles. Dissolved and particulate trace metals within the water column may vary due to primary production, temperature, and nutrient changes, factors that may also vary spatially and temporally. Furthermore, assessment of trace metals mainly relies on in situ observation, and so wide-area investigation of trace-metal concentration may be challenging and subject to technical constraints. A specific approach is therefore necessary that combines biogeochemical proxies, satellite data, and trace-metal linear correlation. This study aims to assess the potential spatio-temporal variability of sea surface cadmium (Cd) and copper (Cu) concentrations in Indonesian seas and surrounding areas. The correlations of Cd and Cu concentrations with primary production and nutrient data were used to convert hindcast satellite data into estimates of the metals' concentrations. The potential variability of trace metals can be determined by overlaying both data. Indonesia's Fisheries Management Areas (FMAs) were used for data clustering and analysis. The results show that Cd and Cu trace metals have similar distribution patterns throughout the year. However, dissolved Cu has a more diverse coverage area than dissolved Cd, including within the Halmahera, Seram, and Maluku Seas (FMAs 716 and 717), the Makassar Strait (FMA 717), and the Java-Sumatra upwelling area (FMA 573). Both Cd and Cu concentrations in the Java-Sumatra upwelling region follow the periodic upwelling pattern. Overall, both Cd and Cu show a declining trend in concentration from 2012 to 2019. It is estimated that dissolved Cd concentration declined from 1500-2000 pmol/kg in 2012 to 1000-1500 pmol/kg in 2019 for all locations. Dissolved Cu concentration decreased from 30-35 nmol/kg in 2012 to 25-30 nmol/kg in 2019. Estimated dissolved Cd and Cu follow the linear functions of silicate (SiO₄), nitrate (NO₃), and primary productivity. The fluctuation of anthropogenic activities and global warming are likely to indirectly impact the decline in metal concentrations by affecting nutrients and primary productivity.

Sea snail (Hexaplex trunculus) and sea cucumber (Holothuria polii) as potential sentinel species for organic pollutants and trace metals in coastal ecosystems

The seasonal bioaccumulation of trace metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs) in sea snail (Hexaplex trunculus) and sea cucumber (Holothuria polii) from Mar Menor lagoon were characterised. The highest concentrations of p,p'-DDE were detected in the central and south part of Mar Menor lagoon. However, the highest concentrations of metals in sea snail and holothurians were detected in the influence area of El Beal wadi. Biomagnification factors (BMF) in sea snail from cockle (sea snail-cockle concentration ratio) were higher than 5 for metal and organochlorinated compounds. However, similar concentrations were observed in both species for PAHs due to gastropods capability of metabolising these pollutants. Consequently, sea snail is proposed as a sentinel for trace metals, PCBs and OCPs in the coastal lagoons, not only due to its bioaccumulation and biomagnification capacity but also the easy sampling and amply distribution in many coastal areas.

Metal and metallothionein levels in zooplankton in relation to environmental exposure: spatial and temporal variability (Saronikos Gulf, Greece)

Metal and metallothionein (MT) in mixed zooplankton were investigated as means of monitoring metal availability regarding environmental exposure. Spatial and temporal variability of Cd, Cu, Ni, Zn, Fe, Mn and Pb in zooplankton and seawater were studied in Saronikos Gulf (Aegean Sea, Eastern Mediterranean), once every second month during an annual cycle (2011-2012). Particulate organic carbon and chlorophyll α were also measured in seawater samples. Median zooplankton metal concentrations were 0.65, 32.4, 7.1, 864, 1420, 40.2 and 26.8 μg g^-1 dw for Cd, Cu, Ni, Zn, Fe, Mn and Pb, respectively, and 109 μg g^-1 ww for MTs. Metal levels in zooplankton and MTs were higher at sites influenced by human-derived pressures. Additionally, metal concentrations in pelagic fish flesh from the Greek MED-POL data base were used for bioconcentration and biomagnification factors calculation. Bioconcentration from water to zooplankton was higher than metal transfer from either seston to zooplankton or zooplankton to fish.

Heavy metal concentrations in wild and farmed gilthead sea bream from southern Mediterranean Sea-human health risk assessment

Arsenic, cadmium, copper, lead, and zinc concentrations in the edible part of wild and farmed Sparus aurata from Algerian coastal were determined. The highest concentrations of cadmium (0.0078 mg kg^-1 wet weight), copper (0.98 mg kg^-1 w.w), and zinc (5.1 mg kg^-1 w.w) were recorded in farmed sea bream, whereas the highest arsenic (5.02 mg kg^-1 w.w) and lead (0.006 mg kg^-1 w.w) levels were registered in wild one. The statistical analysis (Friedman test, p < 0.05) indicated that the origin of fish (wild, farmed in a cage, and farmed in raceway) has relevance to the distribution of metal. Estimated weekly intake of inorganic arsenic, cadmium, and lead for a 72.5-kg person consuming Sparus aurata from Algeria does not exceed 1% of the WHO/JECFA recommended rate for all metals, certainly due to the limited consumption of seafood products by the local population. The total target hazard index is far less than "one" 1, and the carcinogenic risk for arsenic exceeds the acceptable value of 10^-5. Based on the result of this study, the potential risk to human health from the consumption of contaminate farmed sea bream (in the cage) should be considered.

Different trophodynamics between two proximate estuaries with differing degrees of pollution

Mangroves are complex ecosystems with widely varying abiotic factors such as salinity, pH, redox potential, substratum particle size, dissolved organic matter and xenobiotic concentrations, and a high biodiversity. This paper presents the trophodynamic pathways of accumulation and transfer of metals and metalloids (B, Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Ag, As, Se, Rb, Sr, Pb and Hg), in three trophic chains (plant-crab-fish, plankton-shrimp-fish and plankton-oyster) of similar food webs, corresponding to two mangrove estuaries (Santa Cruz and Vitória Bay, separated by 70 km) in the Espírito Santo State (Brazil). Although the trophic transfer patterns are affected by physical variables, metal and metalloids were found in all trophic levels. We observed similar trophodynamics between both estuaries with some elements, but unequal transfer patterns in other cases, thus questioning the effectiveness of ¹⁵N to determine the food chain when the aquatic biota is affected by anthropogenic contaminants. Thus, in the Santa Cruz estuary, most metals were biomagnified through the food web. Conversely, Vitória Bay presented mostly biodilution, suggesting that metal/metalloid transference patterns in mangrove ecosystems may be affected by different anthropogenic contamination inputs. These results indicate the importance of knowing the complete food web when evaluating the trophic transfer of elements, including an evaluation of the differential impact of pollution on diverse components of the food chain.

Organochlorine pesticides and heavy metals in the zooplankton, fishes, and shrimps of tropical shallow tidal creeks and the associated human health risk

Studies on organochlorine pesticides (OCPs) and heavy metals (HMs) from tidal creeks are scarce. Sixteen OCPs and seven HMs were measured in the surface water, zooplankton, two fishes (Harpadon nehereus and Pampus argenteus), and one shrimp (Penaeus indicus) collected from three tidal creeks of the Indian Sundarban. The surface water was polluted by hexachlorocyclohexane isomers (ΣHCH: 525-1581 ng l^-1), dichlorodiphenyltrichloroethane congeners (ΣDDT: 188-377 ng l^-1), endosulfan congeners (ΣEND: 687-1474 ng l^-1), and other OCPs (512-1334 ng l^-1). However, the mean HM concentrations in the surface water were <1 μg l^-1. The zooplankton community exhibited bioaccumulation of both OCPs and HMs. Aldrin, Heptachlor, and α-HCH levels in the edible biotas could lead to cancer. Co and Cd levels could lead to non-cancerous risks, and Pb levels could pose a cancerous risk. This study showed that creeks could be potential sites of both OCP and HM pollution.

Species-specific bioaccumulation of trace metals among fish species from Xincun Lagoon, South China Sea

Xincun Lagoon is an important fishing area in northern Hainan Island, China. It has long been exposed to pollutants from local sewage, breeding cages and fishing boats, resulting in serious pollution threats to the survival of fish. In this study, we examined the concentrations of seven trace metals (Cu, Pb, Zn, Cd, Hg, As and Cr) in sixteen economic fish species collected from Xincun Lagoon and their exposed environment (water and sediment). The concentrations of Pb and Zn in the water column were higher than the safety threshold stipulated by Chinese legislation, while the contents of all examined metals in the sediment and fish species were lower than the legislative thresholds set by China and international organizations. The contents of trace metals in the fish species in high trophic levels or those that prefer to live in/on the sediment layer were significantly higher than those in other trophic levels and pelagic/subbenthic fish, these species had homogeneous anthropogenic pollution sources for Cu, Zn, Cd, Hg and As. Our results show that the trace metal contents in fish were mainly affected by trophic level and habitat preference. The contribution of metal exposure from the sediment to metal accumulation in fish was lower than that in water, especially for the Cd and Hg in the sediment. These results provide valuable information for further understanding the species-specific patterns of metal accumulation in fish and the development of targeted conservation measures for the environment and fish consumers.

Tessier sequential extraction on 17 elements from three marine sediment certified reference materials (HISS-1, MESS-4, and PACS-3)

The four-step Tessier sequential extraction procedure is a well-known approach used for environmental and geochemical studies in soil and sediments. However, a lack of reference materials limits its use making implementation and quality control cumbersome. This study applied Tessier sequential extraction to three globally used marine sediment certified reference materials (CRMs) including HISS-1, MESS-4, and PACS-3 with varying levels of contamination. The study analyzed the distribution of 17 elements throughout the extraction phases. Overall, the percent recovery (sum of steps vs total metal concentration) of all analyzed elements in Tessier extraction was 92% + 40% in HISS-1, 101% + 12% in MESS-4, and 102% + 10% in PACS-3. The observed uncertainty of the individual elemental concentrations averaged at 13%, which compares favorably with the 16% target uncertainty derived from the Horwitz equation. The reference data set produced here using the Tessier sequential extraction procedure will serve as a quality control and method development tool for laboratories. Graphical abstract.

Bioavailability and ecological risks of trace metals in bottom sediments from Doce river continental shelf before and after the biggest environmental disaster in Brazil: The collapse of the Fundão dam

The present study deals with bioavailability of trace metals in the Doce river continental shelf, southeast of Brazil. The bottom sediments of the study area were firstly sampled a few weeks before the biggest environmental disaster of Brazil, the collapse of the Fundão dam in November of 2015. The disaster released around 40 Mm³ of iron ore tailings into Doce river basin and an estimate of 10 Mm³ reached the river delta, having the adjacent continental shelf as the final destination. One year and a half later, on April of 2017, the continental shelf was sampled again. A total of 48 stations were evaluated concerning concentrations of trace metals (Zn, Cu, Pb, Ni, Cr) and other ancillary variables before and after the accident. Trace metals were determined through fractionation in order to assess mobility and establish the ecological risk through RAC index. Before the accident, trace metals mobility was Pb > Ni > Cu > Zn > Cr, with Pb Cu, Ni and posing high ecological risk (RAC>30%) in many stations. Differences in concentrations of metal from pre to post accident were significant, and the increase of trace metals was observed. The mobility order after the accident changed to: Cu > Pb > Ni > Zn > Cr. Metal fractionation showed remarkable changes after the accident, with elements such as Cu, Ni and Zn highly associated with reducible fractions originated from the tailings composition. Despite the decrease of RAC to medium risk after the accident in most stations, the bioavilability of Cu, Pb, Ni and Zn increased as show by their higher accumulation in the bioavailable fractions.

Bioconcentration and depuration of cadmium in the selected tissues of rare minnow (Gobiocypris rarus) and the effect of dietary mulberry leaf supplementation on depuration

A 56-day trial was conducted to elucidate the bioconcentration and depuration of Cd in the liver and muscle of rare minnow (Gobiocypris rarus) and determine the effect of dietary mulberry leaf supplementation on depuration. Juvenile rare minnow were exposed to environmentally relevant doses of Cd (1 and 10 μg/L) for 28 days of uptake and then allowed 28 days of depuration. The bioaccumulation factors of the treated rare minnow in the liver and muscle were calculated to be between 4.13-4.675 and 1.76-1.94, respectively. This results suggested that Cd had high potential for bioconcentration in rare minnow. To investigate the effect of dietary mulberry leaf supplementation on depuration, the remaining fish of each group were allowed to depurate with different ratios (0%, 10%, and 30% dry weight) of dietary mulberry leaf supplementation for an additional 28 days. Fish weights did not differ significantly (p >  0.05) between the control and mulberry leaf treated groups. Mulberry leaf powder did not significantly affect Cd depuration in the 10 μg/L group or in the muscle of the 1 μg/L group, but caused a significant decrease in Cd content in the liver of the 1 μg/L group (p <  0.05). This work was the first to model the bioconcentration of Cd in rare minnow and showed that mulberry leaf supplementation decreased Cd residues in the liver of the 1μg/L group. Such a finding may promote the development of new approaches to mitigate the potential hazards of heavy metals to human health.