Assessment of total and organic mercury levels in blue sharks (Prionace glauca) from the south and southeastern Brazilian coast

Global mercury concentrations in biota: their use as a basis for a global biomonitoring framework

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention's progress to reduce the impact of global Hg pollution on people and the environment.

Assessment of potential risks to human health associated with trace elements in three commercially important shark species captured in the Central Mexican Pacific

Shark meat is a popular protein source worldwide. However, existing national control policies for ensuring the safety and quality of shark meat are minimal. There are concerns about the sustainability of shark populations, which bioaccumulate and biomagnify potentially toxic elements at higher rates than non-predatory fish, posing a risk to human health. In this study, the contributions of essential elements to the Recommended Dietary Allowance (RDA) and potentially toxic elements to the Reference Dose (RfD) linked to shark consumption (200 g per week) were investigated for three shark species in the Central Mexican Pacific. We estimated risks and benefits for women, children, and men. Our results suggest that the three shark species are sources of Se, Co, Cr, Cu, Fe, and Zn, but poor sources of Mn for women and men aged 19-50 years. A weekly ingestion of 200 g of shark meat exceeded the RfD-As by 4-14 times and the RfD-Pb by 1.1-1.7 times for adults, indicating a potential risk to human health. The three shark species were also significant sources of potentially toxic elements for children, including Hg, Cd, Cr, and Pb. An excessive intake of Se was observed, with levels at 8.4-10.6 and 4.3-5.3 times the RDA for children aged 1-8 and 9-13 years, respectively. Although shark meat can be a good source of essential nutrients, the lack of controls in the commercialization process indicates that it should be consumed in moderation due to the potential risks associated with excessive exposure to potentially toxic elements. This caution is particularly important for children and pregnant women, who are at higher risk of health complications from consuming contaminated food.

Impacts of water pollutants on chondrichthyans species from South America: A review

This is the first research that extensively compiles all the available scientific literature on the presence of trace metals (TMs), persistent organic pollutants (POPs), and plastic debris in Chondrichthyan species inhabiting South America (including the Atlantic and Pacific Oceans), providing an insight into Chondrichthyans as bioindicators of pollutants as well as the impacts of pollutant exposure on the organisms. Seventy-three studies were published in South America between 1986 and 2022. While 68.5% focused on TMs, 17.8% on POPs, and 9.6% on plastic debris. Brazil and Argentina were at the top in terms of the number of publications; however, there is an absence of information regarding pollutants for Chondrichthyans in Venezuela, Guyana, and French Guiana. Of the 65 Chondrichthyan species reported, 98.5% belong to the Elasmobranch group, and 1.5% from the Holocephalans. Most studies focused on Chondrichthyans of economic importance, and the most analyzed organs were the muscle and liver. There is a lack of studies on Chondrichthyan species with low economic value and critical conservation status. Due to their ecological relevance, distribution, accessibility, high trophic position, capacity to accumulate high levels of pollutants, and the number of studies published, Prionace glauca and Mustelus schmitii seem to be adequate to serve as bioindicators. For TMs, POPs, and plastic debris there is a lack of studies focusing on the pollutant levels as well as their effect on Chondrichthyans. Future research reporting TMs, POPs, and plastic debris occurrences in Chondrichthyan species are required in order to increase the scarce databases about pollutants in this group, with a clear need for further research on the responses of chondrichthyans to pollutants, as well as making inferences about the potential risks to the ecosystems and human health.

Mercury in oceanic upper trophic level sharks and bony fishes - A systematic review

Anthropogenic activities contribute to nearly half of current Hg emissions to the atmosphere. In the marine habitat, oceanic predator fishes bioaccumulate Hg throughout their lives, making their consumption the main route of Hg exposure in humans. In this context, several publications, between 1973 and 2022, were selected, analyzed, and duly compiled, with the objective to investigate Hg contamination in nine species of bony fish: Thunnus thynnus (8 publications), Thunnus albacares (19), Thunnus obesus (7), Thunnus atlanticus (5), Thunnus alalunga (4), Katsuwonus pelamis (8), Xiphias gladius (18), Coryphaena hippurus (7) and Euthynnus alletteratus (4), as well as two species of cartilaginous fishes Prionace glauca (13 publications) and Isurus oxyrinchus (8). These studies totaled 5973 individuals. We classified species according to taxonomic groups and region of capture and found a significant difference between sharks and bony fishes, with higher Hg concentrations in sharks. The regions of occurrence were divided into 4 large areas (North Atlantic - NAO, South Atlantic - SAO, Equatorial Atlantic Ocean - EAO, and Mediterranean - MED), but no significant differences were observed when comparing the overall Hg concentrations in fish among regions (including all species). Additionally, a thorough discussion of the risks associated with human consumption of these species was conducted, as nine of the selected species presented individuals with Hg concentration values that exceeded the safety limits (1 ppm) set by health agencies worldwide.

Understanding the role of ecological factors affecting mercury concentrations in the blue shark (Prionace glauca)

Human activities have increased environmental concentrations of pollutants in marine ecosystems, which can cause harmful effects on marine organisms. Top predators are particularly susceptible to bioaccumulation and biomagnification of pollutants through the food webs and are described as good sentinels for monitoring metal accumulation such mercury (Hg) in marine ecosystems. However, to be used as sentinels, it is important to understand the main ecological factors affecting the concentrations of pollutants in these organisms. In the present study, our main objective was to investigate the effect of body size, sex, trophic niche and geographic area on Hg concentrations in a top marine top predator, the blue shark (Prionace glauca). We analysed Hg in muscle samples from male and female blue sharks of different body sizes collected from the waters surrounding the Canary Islands and the South of Portugal, in the Atlantic Ocean, to waters of the north-western Mediterranean Sea. The results revealed that the sampling area was an important factor explaining Hg concentrations, showing higher values in the Mediterranean blue sharks. We also found a positive relationship between Hg concentrations and body size of blue sharks, indicating a bioaccumulation process of this pollutant in relation with body size. Moreover, we observed a relationship between Hg concentrations and δ¹³C values, a proxy of the use of inshore-offshore marine habitats. Individuals with depleted δ¹³C values that potentially foraged in offshore waters showed higher Hg values. Importantly, most of the analysed blue sharks presented Hg concentrations that exceeded the limits established by the European Union for human consumption.

Assessment of contaminants in blue sharks from the Northeast Atlantic: Profiles, accumulation dynamics, and risks for human consumers

Chemical pollution is a major threat to marine ecosystems, and top predators such as most shark species are extremely vulnerable to being exposed and accumulating contaminants such as metals and persistent organic pollutants (POPs). This work aimed to study the degree, composition, and the sources of contamination in the blue shark (Prionace glauca) inhabiting the Northeast Atlantic, as well as the potential risk faced by human consumers. A total of 60 sharks were sampled in situ aboard fishing vessels, and the concentrations of a set of metals and POPs were analysed in various tissues and complemented with stable isotope analyses. High levels of contaminants were found in most sharks sampled. The concentrations of most metals were higher in the muscle when compared with the liver. Regarding the dangers to consumers posed by the concentrations of arsenic (As), mercury (Hg), and lead (Pb), over 75% of the sharks presented muscle concentrations of at least one contaminant above the legal limits for human consumption, and a risk assessment determined that consumption of meat of these sharks exceeding 0.07 Kg per week could potentially expose human consumers to dangerous amounts of methylmercury (MeHg). Additionally, the assessment of single contaminants may lead to an underestimation of the risk for the human health. Finally, the overall accumulation of contaminants seems to be mostly influenced by the sharks' geographical distribution, rather than sex, size, or trophic level of their prey.

Mercury and Cadmium Concentrations in Muscle Tissue of the Blue Shark (Prionace glauca) in the Central Eastern Pacific Ocean

Blue sharks (Prionace glauca) are an important resource in Ecuador's fisheries; however, biological and ecological information of this species in the area is scarce. The goal of this study was to determine Hg and Cd concentration levels in muscle tissue, as well as its relationship with size, sex, and sexual maturity stages. A total of 80 specimens (34 females and 46 males) collected from the Ecuadorian longline fishing fleet between June and December 2012 were examined. Sizes for females ranged from 97 to 280 cm total length, with values of Hg between 0.20 to 2.38 mg kg^-1 wet weight (x̄ = 0.71, ± 0.61) and values of Cd between 0.01 and 0.12 mg kg^-1 (x̄ = 0.04, ± 0.02). Sizes for males ranged from 137 to 290 cm TL with values of Hg between 0.17 and 2.94 mg kg^-1 (x̄ = 0.81, ± 0.68) and Cd concentrations between 0.01 and 0.12 mg kg^-1 (x̄ = 0.04, ± 0.03). A Spearman's rank correlation showed a medium positive association between TL and Hg concentrations (ρ = 0.66; p < 0.05), but there was no correlation between TL and Cd concentrations (ρ = 0.00, p < 0.05). Of the analyzed sharks, 46% and 20% had Hg and Cd concentrations, respectively, greater than the limit established by authorities for fishes consumed by humans.

Foraging plasticity diversifies mercury exposure sources and bioaccumulation patterns in the world's largest predatory fish

Large marine predators exhibit high concentrations of mercury (Hg) as neurotoxic methylmercury, and the potential impacts of global change on Hg contamination in these species remain highly debated. Current contaminant model predictions do not account for intraspecific variability in Hg exposure and may fail to reflect the diversity of future Hg levels among conspecific populations or individuals, especially for top predators displaying a wide range of ecological traits. Here, we used Hg isotopic compositions to show that Hg exposure sources varied significantly between and within three populations of white sharks (Carcharodon carcharias) with contrasting ecology: the north-eastern Pacific, eastern Australasian, and south-western Australasian populations. Through Δ²⁰⁰Hg signatures in shark tissues, we found that atmospheric Hg deposition pathways to the marine environment differed between coastal and offshore habitats. Discrepancies in δ²⁰²Hg and Δ¹⁹⁹Hg signatures among white sharks provided evidence for intraspecific exposure to distinct sources of marine methylmercury, attributed to population and ontogenetic shifts in foraging habitat and prey composition. We finally observed a strong divergence in Hg accumulation rates between populations, leading to three times higher Hg concentrations in large Australasian sharks compared to north-eastern Pacific sharks, and likely due to different trophic strategies adopted by adult sharks across populations. This study illustrates the variety of Hg exposure sources and bioaccumulation patterns that can be found within a single species and suggests that intraspecific variability needs to be considered when assessing future trajectories of Hg levels in marine predators.

Mercury, selenium and cadmium in juvenile blue (Prionace glauca) and smooth hammerhead (Sphyrna zygaena) sharks from the Northwest Mexican Pacific coast

Cadmium, selenium, and mercury concentrations were measured in muscle and liver of juvenile blue (Prionace glauca) and smooth hammerhead (Sphyrna zygaena) sharks caught on the west coast of Baja California Sur, Mexico, to evaluate the human health risk associated with its consumption. Cd and Hg were lower than the maximum allowable limit for human consumption established by the Mexican government (Hg = 1.0 μg g^-1 and Cd = 0.50 μg g^-1). Interspecific differences in trace elements accumulation denoted diet variations and physiological requirements of each shark species. Calculated biomagnification factor (BMF) values confirmed a prey-predator trophic transfer of elements. Not significant results of Selenium health benefit Index value (P. glauca = -0.46; S. zygaena = -0.02) signify no potential risks for human health. However, calculated Hazard Index values displayed possible health hazards to the children who consume blue shark meat regularly. The local population is advised regarding the ingestion rates of shark.

Foraging depth depicts resource partitioning and contamination level in a pelagic shark assemblage: Insights from mercury stable isotopes

The decline of shark populations in the world ocean is affecting ecosystem structure and function in an unpredictable way and new ecological information is today needed to better understand the role of sharks in their habitats. In particular, the characterization of foraging patterns is crucial to understand and foresee the evolution of dynamics between sharks and their prey. Many shark species use the mesopelagic area as a major foraging ground but the degree to which different pelagic sharks rely on this habitat remains overlooked. In order to depict the vertical dimension of their trophic ecology, we used mercury stable isotopes in the muscle of three pelagic shark species (the blue shark Prionace glauca, the shortfin mako shark Isurus oxyrinchus and the smooth hammerhead shark Sphyrna zygaena) from the northeastern Pacific region. The Δ¹⁹⁹Hg values, ranging from 1.40 to 2.13‰ in sharks, suggested a diet mostly based on mesopelagic prey in oceanic habitats. We additionally used carbon and nitrogen stable isotopes (δ¹³C, δ¹⁵N) alone or in combination with Δ¹⁹⁹Hg values, to assess resource partitioning between the three shark species. Adding Δ¹⁹⁹Hg resulted in a decrease in trophic overlap estimates compared to those based on δ¹³C/δ¹⁵N alone, demonstrating that multi-isotope modeling is needed for accurate trophic description of the three species. Mainly, it reveals that they forage at different average depths and that resource partitioning is mostly expressed through the vertical dimension within pelagic shark assemblages. Concomitantly, muscle total mercury concentration (THg) differed between species and increased with feeding depth. Overall, this study highlights the key role of the mesopelagic zone for shark species foraging among important depth gradients and reports new ecological information on trophic competition using mercury isotopes. It also suggests that foraging depth may play a pivotal role in the differences between muscle THg from co-occurring high trophic level shark species.

Trophic ecology of sympatric batoid species (Chondrichthyes: Batoidea) assessed by multiple biogeochemical tracers (δ13C, δ15N and total Hg)

Aquatic pollution is known to reduce biodiversity and disrupt wildlife populations. Mercury (Hg) pollution is pervasive worldwide, contributing to the degradation of ecosystems, and causing deleterious effects to exposed organisms and populations. Batoids have a life history linked to the benthic substrate of coastal areas and occupy upper trophic levels. These combined with large bodies, long lifespan, and slow growth rates contributes to increased uptake and accumulation of Hg. However, mechanisms governing these associations are not well understood. Using multiple biogeochemical tracers (δ¹³C, δ¹⁵N and total Hg), we describe trophic interactions of three sympatric batoid species inhabiting an urbanized estuary and identify diet sources that contribute to Hg accumulation and trophic position among these mesopredators. We also use the Bat-ray (Myliobatis californica) as a model species, to compare diet composition, trophic position, and isotopic niche between two populations in two Californian bays. Trophic plasticity in M. californica was characterized by isotopic niche, diet proportions, and trophic position estimates using Bayesian statistics. We found diet and local contamination background strongly associated with Hg accumulation, and Hg levels that exceed EPA water quality criterion (<0.3 μg.g^-1 w.w.) in all studied species.

Concentrations and stable isotopes of mercury in sharks of the Galapagos Marine Reserve: Human health concerns and feeding patterns

The human ingestion of mercury (Hg) from sea food is of big concern worldwide due to adverse health effects, and more specifically if shark consumption constitutes a regular part of the human diet. In this study, the total mercury (THg) concentration in muscle tissue were determined in six sympatric shark species found in a fishing vessel seized in the Galapagos Marine Reserve in 2017. The THg concentrations in shark muscle samples (n = 73) varied from 0.73 mg kg^-1 in bigeye thresher sharks (Alopias superciliosus) to 8.29 mg kg^-1 in silky sharks (Carcharhinus falciformis). A typical pattern of Hg bioaccumulation was observed for all shark species, with significant correlation between THg concentration and shark size for bigeye thresher sharks, pelagic thresher sharks (Alopias pelagicus) and silky sharks. Regarding human health concerns, the THg mean concentration exceeded the maximum weekly intake fish serving in all the studied species. Mass-Dependent Fractionation (MDF, δ²⁰²Hg values) and Mass-Independent Fractionation (MIF, Δ¹⁹⁹Hg values) of Hg in whitetip sharks (Carcharhinus longimanus) and silky sharks, ranged from 0.70‰ to 1.08‰, and from 1.97‰ to 2.89‰, respectively. These high values suggest that both species are feeding in the epipelagic zone (i.e. upper 200 m of the water column). While, blue sharks (Prionace glauca), scalloped hammerhead sharks (Shyrna lewini) and thresher sharks were characterized by lower Δ¹⁹⁹Hg and δ²⁰²Hg values, indicating that these species may focus their foraging behavior on prey of mesopelagic zone (i.e. between 200 and 1000 m depth). In conclusion, the determination of THg concentration provides straight-forward evidence of the human health risks associated with shark consumption, while mercury isotopic compositions constitute a powerful tool to trace the foraging strategies of these marine predators. CAPSULE: A double approach combining Hg concentrations with stable isotopes ratios allowed to assess ontogeny in common shark species in the area of the Galapagos Marine Reserve and the human health risks concern associated to their consumption.

The consumption of shark meat in the Amazon region and its implications for human health and the marine ecosystem

Here, we evaluated the levels of As, Hg, Pb, and Cd in shark meat sold along the Amazon Coast of Brazil and used nitrogen stable isotope values to determine trophic position and to assess element biomagnification. From market samples, a total of 13 species were identified via molecular analysis, including those listed as endangered and vulnerable by the IUCN Red List. Arsenic was present in significantly higher concentrations than all other elements, followed by Hg, with the highest mean concentrations recorded in M. higmani (As: 19.46 ± 8.79 μg/g ww) and C. acronotus (Hg: 1.12 ± 0.68 μg/g ww). Lead and Cd were recorded at much lower levels in all species. The EWI of individual elements were above PTWI for all species when considering Hg, seven species for inorganic arsenic (iAs), and one species for Pb. The weekly consumption of 10 species should be reduced to less than 416.39 g, which is equivalent to the daily estimated fish consumption rate in the region. The mean (±SD) δ¹⁵N values of species ranged from 10.7 ± 0.51‰ in M. higmani to 14.2 ± 0.59‰ in C. porosus, indicating feeding over >1 trophic level. Arsenic was negatively correlated with δ¹⁵N values, while Hg was positively correlated indicating biodilution and biomagnification, respectively. Our results indicate that the sale and consumption of shark meat will expose consumers to potentially harmful levels of iAs and Hg, as well as contributing to the population decline of species including those that are currently categorized as threatened.

The Twilight Zone as a Major Foraging Habitat and Mercury Source for the Great White Shark

The twilight zone contains the largest biomass of the world's ocean. Identifying its role in the trophic supply and contaminant exposure of marine megafauna constitutes a critical challenge in the context of global change. The white shark (Carcharodon carcharias) is a threatened species with some of the highest concentrations of neurotoxin methylmercury (MeHg) among marine top predators. Large white sharks migrate seasonally from coastal habitats, where they primarily forage on pinnipeds, to oceanic offshore habitats. Tagging studies suggest that while offshore, white sharks may forage at depth on mesopelagic species, yet no biochemical evidence exists. Here, we used mercury isotopic composition to assess the dietary origin of MeHg contamination in white sharks from the Northeast Pacific Ocean. We estimated that a minimum of 72% of the MeHg accumulated by white sharks originates from the consumption of mesopelagic prey, while a maximum of 25% derives from pinnipeds. In addition to highlighting the potential of mercury isotopes to decipher the complex ecological cycle of marine predators, our study provides evidence that the twilight zone constitutes a crucial foraging habitat for these large predators, which had been suspected for over a decade. Climate change is predicted to expand the production of mesopelagic MeHg and modify the mesopelagic biomass globally. Considering the pivotal role of the twilight zone is therefore essential to better predict both MeHg exposure and trophic supply to white sharks, and effectively protect these key vulnerable predators.

Are concentrations of pollutants in sharks, rays and skates (Elasmobranchii) a cause for concern? A systematic review

This review represents a comprehensive analysis on pollutants in elasmobranchs including meta-analysis on the most studied pollutants: mercury, cadmium, PCBs and DDTs, in muscle and liver tissue. Elasmobranchs are particularly vulnerable to pollutant exposure which may pose a risk to the organism as well as humans that consume elasmobranch products. The highest concentrations of pollutants were found in sharks occupying top trophic levels (Carcharhiniformes and Lamniformes). A human health risk assessment identified that children and adults consuming shark once a week are exposed to over three times more mercury than is recommended by the US EPA. This poses a risk to local fishing communities and international consumers of shark-based products, as well as those subject to the widespread mislabelling of elasmobranch products. Wider screening studies are recommended to determine the risk to elasmobranchs from emerging pollutants and more robust studies are recommended to assess the risks to human health.

Mercury isotopes as tracers of ecology and metabolism in two sympatric shark species

In coastal ecosystems, top predators are exposed to a wide variety of nutrient and contaminant sources due to the diversity of trophic webs within inshore marine habitats. Mercury contamination could represent an additional threat to shark populations that are declining worldwide. Here we measured total mercury, carbon and nitrogen isotopes, as well as mercury isotopes, in two co-occurring shark species (the bull shark Carcharhinus leucas and the tiger shark Galeocerdo cuvier) and their potential prey from a coastal ecosystem of the western Indian Ocean (La Réunion Island). Our primary goals were to (i) determine the main trophic Hg sources for sharks and (ii) better characterize their diet composition and foraging habitat. Hg isotope signatures (Δ¹⁹⁹Hg and δ²⁰²Hg) of shark prey suggested that bull sharks were exposed to methylmercury (MeHg) produced in offshore epipelagic waters, while tiger sharks were exposed to offshore mesopelagic MeHg with additional microbial transformation in slope sediments. Δ¹⁹⁹Hg values efficiently traced the ecology of the two predators, demonstrating that bull sharks targeted coastal prey in shallow waters while tiger sharks were mainly foraging on mesopelagic species in the deeper waters of the island slope. Unexpectedly, we found a positive shift in δ²⁰²Hg (>1‰) between sharks and their prey, leading to high δ²⁰²Hg values in the two shark species (e.g. 1.91 ± 0.52‰ in bull sharks). This large shift in δ²⁰²Hg indicates that sharks may display strong MeHg demethylation abilities, possibly reflecting evolutionary pathways for mitigating their MeHg contamination.

Mercury concentration in shark meat from traditional markets of Gyeongsangbuk-do, South Korea

Background

Although unusually high levels of blood mercury have been reported in the North Gyeongsang Province (Gyeongsangbuk-do), mercury contents from shark meat distributed in this region have not been assessed yet. Thus, this study aims to identify the hazard by evaluating the mercury contents of the shark meat sold in the traditional market of Gyeongsangbuk-do.

Methods

The shark meat in the form of muscle meat was obtained from 15 traditional markets of Gyeongsangbuk-do in the summer and winter of 2013. Out of 105 samples in total, 49 were collected in the summer and 56 in the winter. The total mercury concentration was measured by the combustion-gold amalgamation method using an automatic mercury analyzer (Milestone DMA-80, Milestone).

Results

The average mercury concentration of shark meat was 2.29 ± 1.77 µg/g, ranging between 0.06–8.93 µg/g with a geometric mean of 1.44 µg/g, which is higher than those reported in many countries. The mercury concentration in 77 of 105 shark meat samples exceeded 1 µg/g. Mercury concentration ranged between 0.09–8.93 µg/g (geometric mean: 1.45) in the summer and 0.06–6.73 µg/g (geometric mean: 1.48) in the winter.

Conclusions

Shark meat sold in the market contained a substantial amount of mercury. This suggests that it is difficult to reduce mercury intake by simply strengthening the standard level of mercury concentration in shark meat. Therefore, it is need to communication and awareness programs with consumers about hazardous effects of mercury inherent in shark meat.

Occurrence and tissue distribution of perfluoroalkyl substances (PFASs) in sharks and rays from the eastern Mediterranean Sea

Persistent organic pollutants (POPs), including Perfluoroalkyl substances (PFASs), enter into the marine ecosystem, raising questions on possible adverse effects caused to the health of marine organisms and especially of top predators. Thus, there is an urge to assess the occurrence and the tissue distribution of PFASs in apex predators. To this end, the current study examines concentrations and distribution of 15 PFASs among 85 samples of different tissues from 9 shark and ray species collected in Greece. The results showed a similar PFAS pattern among the different tissues, with long carbon chain PFASs being the most frequently detected compounds. PFTrDA was the most predominant compound in terms of concentration and frequency of detection, followed by PFUnDA and PFOS. PFTrDA concentrations ranged between < LOQ and 27.1 ng/g ww, while PFUnDA and PFOS levels ranged from <LOQ to 16.0 and < LOQ to 21.6 ng/g ww, respectively. Regarding their frequency of detection, PFTrDA and PFUnDA were detected in 98% and 91% of the samples, respectively, while PFOS was detected in 79%. ΣPFAS concentrations in each analysed tissue ranged from 0.3 to 85 ng/g ww, with the latter being detected in the liver of angular roughshark (Oxynotus centrina). On average, PFASs were found to be accumulated in tissues in the following order: gonads > heart > liver ≈ gills > muscle. Relative contribution (%) of individual compounds to ΣPFAS concentration varied among the different shark tissues, and also among the different shark species. No correlation between PFASs levels in tissues and sharks' gender, length and geographical origin was observed.

Mercurio, metilmercurio y otros metales pesados en peces de Colombia: riesgo por ingesta

En 2013 el pescado proporcionó a más de 3100 millones de personas casi el 20 % de la ingesta promedio de proteínas de origen animal per cápita (FAO, 2016). De acuerdo con el Programa de las Naciones Unidas para el Desarrollo (PNUD), en Colombia y, particularmente en las poblaciones ribereñas y costeras, el 90 % del consumo de proteína de origen animal proviene del pescado, como resultado de un acceso muy bajo a otro tipo de proteínas. Colombia enfrenta uno de los mayores problemas por contaminación ambiental a nivel mundial, generado en gran parte por el abuso de sustancias químicas para el aprovechamiento de minerales, mala disposición de aguas servidas y prácticas industriales y agrícolas inadecuadas, en cuerpos de aguas fundamentales para la dinámica poblacional de animales, vegetales y humanos. Como estrategia mundial para reducir los riesgos a la salud humana por consumo de pescado contaminado con metales pesados, se han considerado límites máximos permisibles, propuestos por diferentes entidades; sin embargo, el 31,5 % de los resultados de estudios publicados para Colombia, son superiores al límite permisible recomendado por la OMS (0,5 μg/g). Los resultados presentados en esta revisión evidencian la urgente necesidad de realizar estudios que evalúen el riesgo a la salud que enfrentan pobladores de zonas mineras y no mineras de Colombia, aportará también fundamentos científicos y bases para el establecimiento de ejes estratégicos que permitan la puesta en marcha de nuevos proyectos productivos que ofrezcan el acceso de la población a diversas fuentes de alimentación.

Trace metals and persistent organic pollutants contamination in batoids (Chondrichthyes: Batoidea): A systematic review

Batoids (Chondrichthyes: Batoidea; e.g. stingrays, skates, and guitarfish) comprise more than 55% of elasmobranch taxa and represent ecologically important predators in benthic and pelagic habitats. Although overexploitation and habitat degradation are the two biggest threats to batoid populations, coastal and oceanic pollution is also a pervasive potential threat. In this systematic review, we compile published scientific literature on trace metals and persistent organic pollutants (POPs) contamination in elasmobranch species of the Batoidea superorder and present contamination patterns, exposure effects, and potential human exposure risks to most reported contaminants. We found batoids to accumulate a wide range of trace metals, including mercury (Hg), arsenic (As), lead (Pb), copper (Cu), cadmium (Cd) and zinc (Zn). Accumulation of POPs is reported for chlordanes, dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyl (PCB), dieldrin, Heptachlor epoxide, hexachlorobenzene and perfluoroalkyl substances (PFAS). Hg levels in muscle tissue were significantly different among oceanic basins and habitats, consistent with previous global assessments of Hg oceanic background levels. Some batoid species presented Hg levels higher than large pelagic teleost fishes and comparable to sharks. Ecological traits such as, bottom feeding, upper trophic position and elasmobranch-specific physiology and metabolism are discussed as potential factors associated with Hg uptake and accumulation in batoids. Some species exceeded USEPA's maximum contamination safety limits in edible tissues for Hg, As and ΣPCBs. For most trace metals and POPs, there is a lack of studies focusing on contamination levels in batoids. We recommend future research increasing reporting on POPs and trace metals besides Hg in batoids to further investigate the role of Elasmobranch as a bioindicator for marine pollution.

Mercury in blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus) from north-eastern Atlantic: Implication for fishery management

Pelagic sharks (blue shark Prionace glauca and shortfin mako Isurus oxyrinchus) caught by long-line Spanish and Portuguese fleets in the NE Atlantic, were sampled at Vigo fish market (Spain) for total mercury (Hg) analysis. Hg concentration in white muscle increased with size and weight in both species, but at a higher rate in shortfin mako than in the blue shark. No difference was found with sex, year and season. Spatial variation was observed in the blue shark with higher Hg values in the North of the Azorean archipelago, but not in the shortfin mako. These high-level predators are particularly susceptible to bioaccumulate contaminants (Hg) in their tissues (muscle). However, a significant positive relationship between Hg concentration and trophic level (δ¹⁵N) of individuals was observed only in the shortfin mako. Most sharks landed were juveniles which presented Hg concentration lower than the maximum limit allowed by the European Union (1mgkg^-1 wet weight) for marketing. However, concentrations above this threshold were most recorded in blue sharks larger than 250cm total length (TL) and in shortfin makos larger than 190cm TL, raising the question of the commercialization of large-sized individuals.

An evaluation of mercury offloading in two Central California elasmobranchs

Elasmobranchs occupy high trophic levels, accumulate high concentrations of mercury in their tissues, and have high energetic levels of maternal investment to offspring, which may cause embryos to be exposed in utero to harmful concentrations of mercury. We investigated the maternal transfer of mercury in two common coastal elasmobranch species, Triakis semifasciata and Platyrhinoidis triseriata, to determine which reproductive parameters may influence mercury offloading, and whether embryos are at risk to mercury toxicity. Mercury concentration was measured in female muscle, female liver, and embryonic tissues. The behavior of mercury in adult female tissues differed between species, as liver mercury concentration was significantly correlated to muscle mercury concentration in P. triseriata but not in T. semifasciata. Embryos of both species were found with potentially harmful mercury concentrations in their muscle tissues. Embryo mercury concentration increased with female muscle mercury concentration, but the relationship to female liver mercury was more variable. The rate of mercury transfer and overall offloading potential were significantly greater in P. triseriata than T. semifasciata. It appears that female mercury concentration, either in muscle or liver, is an important influencing factor for mercury offloading, but the impact of the differing reproductive modes in these two species was less clear. More study on this subject will continue to elucidate the factors influencing mercury offloading in sharks and rays, and how contaminant risk affects populations on a whole.

Mid-Atlantic elasmobranchs: Suitable metal scouts?

Heavy metals are a hazard to marine fauna and human health. In this study we assess stable isotopes and metal content in Prionace glauca and Isurus oxyrinchus and analyse these results within and among other species and across regions and geographical areas. Also, we evaluate their suitability, together with Raja clavata and Galeorhinus galeus, as Mid-Atlantic bioindicators. Prionace glauca and I. oxyrinchus shared the same trophic level in a pelagic food web and did not present significant differences between genders or metals, except for As. Arsenic and Hg accumulated while Cd and Pb were not detected. One I. oxyrinchus presented Hg values above regulatory limits. A high Hg exposure was associated with I. oxyrinchus since its maximum weekly intake was exceeded. Elasmobranchs can be used as metal sentinels, each presenting different key features which defines a good marine bioindicator, allowing long-term monitoring at different temporal and spatial scales.

Blue sharks (Prionace glauca) as bioindicators of pollution and health in the Atlantic Ocean: Contamination levels and biochemical stress responses

Marine ecosystems are constantly being threatened by contaminants produced by human activities. There is an urge to better understand their impacts on marine organisms and develop reliable tools for biomonitoring studies, while also assessing their potential impacts on human health. Given their position on top of food webs, sharks are particularly susceptible to bioaccumulation, making them potential sentinel species of marine contamination. The main objective of this study was to find suitable biomarkers for future marine pollution biomonitoring studies by correlating biochemical responses with tissue contaminant body burden in blue sharks (Prionace glauca), a species heavily caught and consumed by humans, while also addressing their general health. The chemical contaminants analysed comprised different persistent organic pollutants (POPs) families from polychlorinated compounds to brominated flame retardants (BFRs) and perfluorinated compounds (PFCs) and different trace and heavy metals. Concentrations of some contaminants in sharks' tissues were found to be above the legally allowed limits for human consumption. A canonical correspondence analysis (CCA) was performed and some strong associations were found between biochemical responses and contaminants' accumulation levels. DNA damage and lipid peroxidation levels, as well as the inhibition of the antioxidant enzyme glutathione peroxidase, were the main effects and consequences of contamination. The impact of contamination on these vital macromolecules underlines the suboptimal conditions of the sampled P. glauca, which can ultimately lead to the degradation of core ecological aspects, such as swimming, feeding, and reproduction. It can be concluded that P. glauca demonstrates great potential to be used as environmental sentinel and suitable biomarker candidates were identified in this work. Moreover, this study also highlights the risks that the consumption of blue shark derived products can pose to human health, which is of upmost interest as the sampled organisms were still juveniles and already presented values above regulatory limits.