Bioaccumulation of metals and PCBs in Raja clavata

Bioaccumulation and biomagnification of arsenic in the muscle and liver of the speckled guitarfish Pseudobatos glaucostigmus in Santa Rosalía, Gulf of California, Mexico

Arsenic (As) concentrations were measured in the muscle and liver of the speckled guitarfish Pseudobatos glaucostigmus and its main prey Penaeus californiensis, in Santa Rosalia, western Gulf of California, to determine bioaccumulation and biomagnification. Higher mean wet weight (w.w.) values were found in muscle tissue (9.87 μg g-1) compared to liver tissue (5.32 μg g-1); however, the highest concentrations were found in the liver (48.05 μg g-1). All samples showed As concentrations above the maximum permissible limit for human consumption. The highest concentrations in mature females (muscle: 6.93 μg g-1; liver: 14.5 μg g-1) concerning pregnant females (muscle: 5.01 μg g-1; liver: 8.46 μg g-1) may indicate a maternal transfer of As from mothers to their embryos. Arsenic bioaccumulates in the liver, which was evident from the positive correlation between total length and As concentration. Arsenic levels in Penaeus californiensis showed biomagnification from prey to predator for both tissues.

Organochlorine contaminants in Rio skate (Rioraja agassizii), an endangered batoid species, from southeastern coast of Brazil

A global movement towards decreases in elasmobranch overfishing has been noted in the last decades. However, discussion concerning the effects of POP contamination on the health and survival of these organisms is still recent. These compounds can affect the immune and endocrine systems of both sharks and batoids, impairing reproduction and impacting species recruitment, acting synergistically alongside overfishing effects. In this context, this study investigated the concentration of organochlorine compounds in liver of 29 individuals of Rioraja agassizii, a commercially exploited skate classified as Vulnerable by IUCN and as Endangered in Brazil. Contaminant concentrations were higher in adults compared to juveniles. Distinct contamination profiles were observed, suggesting different groups within the investigated population and revealing contaminants as a potential tool to assess population ecology. PCB levels were considered a concern as they resemble concentrations in ecosystems from the northern hemisphere, where deleterious effects on elasmobranchs have been observed.

Additional Pressure to a Threatened Species: High Persistent Organic Pollutant Concentrations in the Tropical Estuarine Batoid Gymnura altavela

Persistent organic pollutants (POPs) were determined in Gymnura altavela liver samples from one of the most impacted estuarine environments in the Atlantic Ocean (Guanabara Bay, Brazil). PCBs were the predominant compounds (91.2%) averaging 6773 ± 4659 ng.g^-1 lipid weight (lw). DDT, Mirex, HCH and HCB concentrations were 633 ± 715, 6.2 ± 9.3, 3.4 ± 1.4 and 0.5 ± 0.5 ng.g^-1 lw, respectively. Recent DDT input in the estuary was minimum, as verified by the p,p'-DDE/∑DDT ratio (0.67). The prevalence of industrial compounds was highlighted by the ΣDDT/ΣPCB ratio (0.08). A negative correlation detected between disc width and PCBs, Mirex and HCH concentrations may be a consequence of maternal offloading. High POP concentrations in G. altavela liver samples from Guanabara Bay suggests that PCBs, in particular, may pressure the conservation of this threatened with extinction tropical estuarine batoid species.

Metal contamination in threatened elasmobranchs from an impacted urban coast

Guitarfishes and angelsharks are two of the most endangered elasmobranch groups. Despite this, limited knowledge exists regarding the effects of environmental contamination in these groups. For this reason, this study assessed the concentrations of metals in liver and muscle of three guitarfishes (Pseudobatos horkelii, P. percellens, and Zapteryx brevirostris) and one angelshark species (Squatina guggenheim) captured during the year of 2019 in one of the most impacted areas in South America: the São Paulo State coast, Brazil, Southwest Atlantic. Cadmium (Cd) Chromium (Cr) Cupper (Cu) Iron (Fe), Mercury (Hg), and Lead (Pb) were determined by atomic spectrometry, with samples being previously acid digested. Among the non-essential metals, Cd had the highest mean concentrations for all species, followed by Pb and Hg, whereas Fe had the highest mean levels among the essential metals analyzed, followed by Cu and Cr. Liver and muscle samples had different concentrations, with liver presenting the highest concentrations. Except for Cd, non-essential metals had relatively low concentrations when compared to other elasmobranch species reported in the literature, which could be explained by the efficiency in metabolizing these compounds or differential life history patterns among the species studied herein and other. Considering that all species analyzed herein are typically consumed, human health impacts must be considered, especially concerning Cd concentrations. Furthermore, Cd, Cr and Pb were above the safety limits, indicating potential hazard for human consumption. In conclusion, our results suggest that these species are exposed to metals and that concentrations above the safety limits observed for these species must be taken into consideration regarding human consumption.

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.

In utero elemental tags in vertebrae of the scalloped hammerhead shark Sphyrna lewini reveal migration patterns of pregnant females

Vertebral microchemistry recently allowed to infer the migration patterns of the scalloped hammerhead shark Sphyrna lewini in the Mexican Pacific, however conclusions regarding the movements of reproductive females were hindered by the small sample size. Considering that S. lewini is a placental viviparous species, maternal supply of nutrients to the embryos might influence their vertebral microchemistry while in utero and provide intrinsic markers of the pregnant female environmental histories. This hypothesis was tested before attempting to infer the migration patterns of pregnant females through the analyses of the in utero elemental profiles quantified in the vertebrae of coastal young-of-the-year (‘YOY’). Vertebrae were obtained from sharks captured along the Mexican Pacific coast in 2016. Vertebral microchemistry was quantified using laser ablation inductively-coupled plasma mass spectrometry. Elemental signatures at vertebral edge were consistent between each pregnant female and her embryos demonstrating the viability of employing in utero elemental signatures as a maternal tag of the gestation-related environmental histories. Analyses of the YOY in utero Sr:Ba and Pb:Ca profiles suggested that pregnant females either (1) progressively migrated offshore before quickly returning to coastal habitats before term or (2) remained nearshore during complete gestation. Considering the endangered status of S. lewini, current management measures may be insufficient for the sustainable management of the population as pregnant females may be particularly susceptible to fisheries when remaining nearshore or entering coastal habitats prior to pupping.

Concentrations of mercury and other trace elements in two offshore skates: sandy ray Leucoraja circularis and shagreen ray L. fullonica

Trace metal concentrations in muscle and liver tissues from two offshore species of skate were examined. Concentrations of mercury in muscle of Leucoraja circularis (n=20; 23-110.5cm total length, 157-490m water depth) and L. fullonica (n=24; 28.5-100cm total length, 130-426m water depth) were 0.02-1.8 and 0.04-0.61mgkg^-1, respectively. Concentrations of both As and Hg increased with total length. Only the largest specimen had a concentration of Hg in muscle >1.0mgkg^-1. Data were limited for specimens>90cm long, and further studies on contaminants in larger-bodied skates could usefully be undertaken.

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.