Accumulation of Per- and Polyfluoroalkyl Substances (PFAS) in Coastal Sharks from Contrasting Marine Environments: The New York Bight and The Bahamas.

Per- and polyfluoroalkyl substances (PFAS) enter the marine food web, accumulate in organisms, and potentially have adverse effects on predators and consumers of seafood. However, evaluations of PFAS in meso-to-apex predators, like sharks, are scarce. This study investigated PFAS occurrence in five shark species from two marine ecosystems with contrasting relative human population densities, the New York Bight (NYB) and the coastal waters of The Bahamas archipelago. The total detected PFAS (∑PFAS) concentrations in muscle tissue ranged from 1.10 to 58.5 ng g-1 wet weight, and perfluorocarboxylic acids (PFCAs) were dominant. Fewer PFAS were detected in Caribbean reef sharks (Carcharhinus perezi) from The Bahamas, and concentrations of those detected were, on average, ∼79% lower than in the NYB sharks. In the NYB, ∑PFAS concentrations followed: common thresher (Alopias vulpinus) > shortfin mako (Isurus oxyrinchus) > sandbar (Carcharhinus plumbeus) > smooth dogfish (Mustelus canis). PFAS precursors/intermediates, such as 2H,2H,3H,3H-perfluorodecanoic acid and perfluorooctanesulfonamide, were only detected in the NYB sharks, suggesting higher ambient concentrations and diversity of PFAS sources in this region. Ultralong-chain PFAS (C ≥ 10) were positively correlated with nitrogen isotope values (δ15N) and total mercury in some species. Our results provide some of the first baseline information on PFAS concentrations in shark species from the northwest Atlantic Ocean, and correlations between PFAS, stable isotopes, and mercury further contextualize the drivers of PFAS occurrence.

Copepod feeding strategy determines response to seawater viscosity: videography study of two calanoid copepod species.

Calanoid copepods, depending on feeding strategy, have different behavioral and biological controls on their movements, thereby responding differently to environmental conditions such as changes in seawater viscosity. To understand how copepod responses to environmental conditions are mediated through physical, physiological and/or behavioral pathways, we used high-speed microvideography to compare two copepod species, Acartia hudsonica and Parvocalanus crassirostris, under different temperature, viscosity and dietary conditions. Acartia hudsonica exhibited 'sink and wait' feeding behavior and typically responded to changes in seawater viscosity; increased seawater viscosity reduced particle-capture behavior and decreased the size of the feeding current. In contrast, P. crassirostris continuously swam and did not show any behavioral or physical responses to changes in viscosity. Both species showed a physiological response to temperature, with reduced appendage beating frequency at cold temperatures, but this did not generally translate into effects on swimming speed, feeding flux or active time. Both copepod species swam slower when feeding on diatom rather than dinoflagellate prey, showing that prey type mediates copepod behavior. These results differentiate species-specific behaviors and responses to environmental conditions, which may lead to better understanding of niche separation and latitudinal patterns in copepod feeding and movement strategies.

An assessment of temporal trends in mercury concentrations in fish.

The importance of fish consumption as the primary pathway of human exposure to mercury and the establishment of fish consumption advisories to protect human health have led to large fish tissue monitoring programs worldwide. Data on fish tissue mercury concentrations collected by state, tribal, and provincial governments via contaminant monitoring programs have been compiled into large data bases by the U.S. Environmental Protection Agency's Great Lakes National Monitoring Program Office (GLNPO), the Ontario Ministry of the Environment's Fish Contaminants Monitoring and Surveillance Program (FMSP), and many others. These data have been used by a wide range of governmental and academic investigators worldwide to examine long-term and recent trends in fish tissue mercury concentrations. The largest component of the trend literature is for North American freshwater species important in recreational fisheries. This review of temporal trends in fish tissue mercury concentrations focused on published results from freshwater fisheries of North America as well as marine fisheries worldwide. Trends in fish tissue mercury concentrations in North American lakes with marked overall decreases were reported over the period 1972-2016. These trends are consistent with reported mercury emission declines as well as trends in wet deposition across the U.S. and Canada. More recently, a leveling-off in the rate of decreases or increases in fish tissue mercury concentrations has been reported. Increased emissions of mercury from global sources beginning between 1990 and 1995, despite a decrease in North American emissions, have been advanced as an explanation for the observed changes in fish tissue trends. In addition to increased atmospheric deposition, the other factors identified to explain the observed mercury increases in the affected fish species include a systematic shift in the food-web structure with the introduction of non-native species, creating a new or expanding role for sediments as a net source for mercury. The influences of climate change have also been identified as contributing factors, including considerations such as increases in temperature (resulting in metabolic changes and higher uptake rates of methylmercury), increased rainfall intensity and runoff (hydrologic export of organic matter carrying HgII from watersheds to surface water), and water level fluctuations that alter either the methylation of mercury or the mobilization of monomethylmercury. The primary source of mercury exposure in the human diet in North America is from the commercial fish and seafood market which is dominated (>90%) by marine species. However, very little information is available on mercury trends in marine fisheries. Most of the data used in the published marine trend studies are assembled from earlier reports. The data collection efforts are generally intermittent, and the spatial and fish-size distribution of the target species vary widely. As a result, convincing evidence for the existence of fish tissue mercury trends in marine fish is generally lacking. However, there is some evidence from sampling of large, long-lived commercially-important fish showing both lower mercury concentrations in the North Atlantic in response to reduced anthropogenic mercury emission rates in North America and increases in fish tissue mercury concentrations over time in the North Pacific in response to increased mercury loading.

Microbial generation of elemental mercury from dissolved methylmercury in seawater.

Elemental mercury (Hg0) formation from other mercury species in seawater results from photoreduction and microbial activity, leading to possible evasion from seawater to overlying air. Microbial conversion of monomethylmercury (MeHg) to Hg0 in seawater remains unquantified. A rapid radioassay method was developed using gamma-emitting 203Hg as a tracer to evaluate Hg0 production from Hg(II) and MeHg in the low pM range. Bacterioplankton assemblages in Atlantic surface seawater and Long Island Sound water were found to rapidly produce Hg0, with production rate constants being directly related to bacterial biomass and independent of dissolved Hg(II) and MeHg concentrations. About 32% of Hg(II) and 19% of MeHg were converted to Hg0 in 4 d in Atlantic surface seawater containing low bacterial biomass, and in Long Island Sound water with higher bacterial biomass, 54% of Hg(II) and 8% of MeHg were transformed to Hg0. Decreasing temperatures from 24°C to 4°C reduced Hg0 production rates cell-1 from Hg(II) 3.3 times as much as from a MeHg source. Because Hg0 production rates were linearly related to microbial biomass and temperature, and microbial mercuric reductase was detected in our field samples, we inferred that microbial metabolic activities and enzymatic reactions primarily govern Hg0 formation in subsurface waters where light penetration is diminished.

Temporal Changes in 137Cs Concentrations in Fish, Sediments, And Seawater off Fukushima Japan.

We analyzed publicly available data of Fukushima 137Cs concentrations in coastal fish, in surface and bottom waters, and in surface marine sediments and found that within the first year of the accident pelagic fish lost 137Cs at much faster rates (mean of ∼1.3% d-1) than benthic fish (mean of ∼0.1% d-1), with benthopelagic fish having intermediate loss rates (mean of ∼0.2% d-1). The loss rates of 137Cs in benthic fish in the first year were more comparable to the decline of 137Cs concentrations in sediments (0.03% d-1), and the declines in pelagic fish were more comparable to the declines in seawater. Retention patterns of 137Cs in pelagic fish were comparable to that in laboratory studies of fish in which there were no sustained 137Cs sources, whereas the benthopelagic and benthic fish species retained 137Cs to a greater extent, consistent with the idea that there is a sustained additional 137Cs source for these fish. These field data, based on 13 511 data points in which 137Cs was above the detection limit, are consistent with conclusions from laboratory experiments that demonstrate that benthic fish can acquire 137Cs from sediments, primarily through benthic invertebrates that contribute to the diet of these fish.

Mercury Stable Isotopes Reveal Influence of Foraging Depth on Mercury Concentrations and Growth in Pacific Bluefin Tuna.

Pelagic ecosystems are changing due to environmental and anthropogenic forces, with uncertain consequences for the ocean's top predators. Epipelagic and mesopelagic prey resources differ in quality and quantity, but their relative contribution to predator diets has been difficult to track. We measured mercury (Hg) stable isotopes in young (<2 years old) Pacific bluefin tuna (PBFT) and their prey species to explore the influence of foraging depth on growth and methylmercury (MeHg) exposure. PBFT total Hg (THg) in muscle ranged from 0.61 to 1.93 µg g-1 dw (1.31 µg g-1 dw ±0.37 SD; 99% ± 6% MeHg) and prey ranged from 0.01 to 1.76 µg g-1 dw (0.13 µg g-1 dw ±0.19 SD; 85% ± 18% MeHg). A systematic decrease in prey δ202Hg and Δ199Hg with increasing depth of occurrence and discrete isotopic signatures of epipelagic prey (δ202Hg: 0.74 to 1.49‰; Δ199Hg: 1.76-2.96‰) and mesopelagic prey (δ202Hg: 0.09 to 0.90‰; Δ199Hg: 0.62-1.95‰) allowed the use of Hg isotopes to track PBFT foraging depth. An isotopic mixing model was used to estimate the dietary proportion of mesopelagic prey in PBFT, which ranged from 17% to 55%. Increased mesopelagic foraging was significantly correlated with slower growth and higher MeHg concentrations in PBFT. The slower observed growth rates suggest that prey availability and quality could reduce the production of PBFT biomass.

Assessing Fukushima-Derived Radiocesium in Migratory Pacific Predators.

The 2011 release of Fukushima-derived radionuclides into the Pacific Ocean made migratory sharks, teleosts, and marine mammals a source of speculation and anxiety regarding radiocesium (134+137Cs) contamination, despite a lack of actual radiocesium measurements for these taxa. We measured radiocesium in a diverse suite of large predators from the North Pacific Ocean and report no detectable (i.e., ≥ 0.1 Bq kg-1 dry wt) Fukushima-derived 134Cs in all samples, except in one olive ridley sea turtle (Lepidochelys olivacea) with trace levels (0.1 Bq kg-1). Levels of 137Cs varied within and across taxa, but were generally consistent with pre-Fukushima levels and were lower than naturally occurring 40K by one to one to two orders of magnitude. Predator size had a weaker effect on 137Cs and 40K levels than tissue lipid content. Predator stable isotope values (δ13C and δ15N) were used to infer recent migration patterns, and showed that predators in the central, eastern, and western Pacific should not be assumed to accumulate detectable levels of radiocesium a priori. Nondetection of 134Cs and low levels of 137Cs in diverse marine megafauna far from Fukushima confirms negligible increases in radiocesium, with levels comparable to those prior to the release from Fukushima. Reported levels can inform recently developed models of cesium transport and bioaccumulation in marine species.

Bioaccumulation of methylmercury in a marine diatom and the influence of dissolved organic matter.

The largest bioconcentration step of most metals, including methylmercury (MeHg), in aquatic biota is from water to phytoplankton, but the extent to which dissolved organic matter (DOM) affects this process for MeHg largely remains unexplored in marine systems. This study investigated the influence of specific sulfur-containing organic compounds and naturally occurring DOM on the accumulation of MeHg in a marine diatom Thalassiosira pseudonana. Initial uptake rate constants and volume concentration factors (VCFs) of MeHg were calculated to evaluate MeHg enrichment in algal cells in the presence of a range of organic compound concentrations. At environmentally realistic and higher concentrations, the addition of glycine and methionine had no effect on algal MeHg uptake, but thiol-containing compounds such as cysteine and thioglycolic acid reduced MeHg accumulation in algal cells at high added concentrations (> 100 times higher than naturally occurring concentrations). However, environmentally realistic concentrations of glutathione, another thiol-containing compound as low as 10 nM, resulted in a decline of ~ 30% in VCFs, suggesting its possible importance in natural waters. Humic acid additions of 0.1 and 0.5 mg C/L also reduced MeHg VCFs by ~ 15% and ~ 25%, respectively. The bioaccumulation of MeHg for T. pseudonana in coastal waters with varying levels of dissolved organic carbon (DOC) was inversely correlated with bulk DOC concentrations. Generally, naturally occurring DOM, particularly certain thiol-containing compounds, can reduce MeHg uptake by phytoplankton.

Methylmercury uptake by diverse marine phytoplankton.

Phytoplankton may serve as a key entry for methylmercury (MeHg) into aquatic food webs however very few studies have quantified the bioconcentration of MeHg in marine phytoplankton from seawater, particularly for non-diatoms. Experiments using 203Hg to measure MeHg uptake rates and concentration factors in six marine phytoplankton species belonging to different algal classes were conducted and the influence of light, temperature, and nutrient conditions on MeHg bioaccumulation were determined. All algal species greatly concentrated MeHg out of seawater, with volume concentration factors (VCFs) ranging from 0.2 × 105 to 6.4 × 106. VCFs were directly related to cellular surface area-to-volume ratios. Most of the cellular MeHg was found in the cytoplasm. Temperature, light, and nutrient additions did not directly affect MeHg uptake in most species, with the exception that the dinoflagellate Prorocentrum minimum displayed significantly greater uptake per cell at 18°C than at 4°C, suggesting an active uptake for this species. Passive transport seemed to be the major pathway for most phytoplankton to acquire MeHg and was related to the surface area-to-volume ratio of algal cells. Environmental conditions that promoted cell growth resulted in more total MeHg associated with cells, but with lower concentrations per unit biomass due to biodilution. The very high bioconcentration of MeHg in marine phytoplankton is by far the largest bioconcentration step in marine food chains and variations in algal uptake may account for differences in the amount of MeHg that ultimately builds up in different marine ecosystems.

Contaminated Marine Sediments As a Source of Cesium Radioisotopes for Benthic Fauna near Fukushima.

Marine animals, seawater, and sediment near Fukushima, Japan have become contaminated with 134Cs and 137Cs released in March 2011 from the damaged Fukushima Dai-ichi nuclear power plant. Radiocesium concentrations in some benthic fauna declined more slowly than in pelagic fish in the same region. We tested the hypothesis that benthic fish remained more contaminated due to the bioavailability of radiocesium in sediments. Laboratory experiments demonstrated that the assimilation efficiency of 137Cs was 16% in polychaetes ingesting Fukushima sediment, up to 55% in crabs ingesting polychaetes, and about 80% in fish ingesting worms. In addition, all animals acquired Cs directly from the aqueous phase, but this accounted for only 1.2-2.5% of their total body burden. Thus, diet accounted for nearly all of the total body burden of Cs in these animals. Rate constants of Cs loss from animal tissues were 20% d-1 for polychaetes, 10% d-1 for crabs, and 6% d-1 for fish after acquisition of Cs from water; rate constants following dietary uptake were 45% d-1, 14% d-1, and 5% d-1 for polychaetes, crabs, and fish, respectively. A bioaccumulation model indicated that the transfer factors of Cs from sediments and the trophic transfer factors from worms to predators were about 1. Overall, sediment-bound Cs is sufficiently bioavailable to deposit-feeding polychaetes, and macrofauna assimilate Cs from these polychaetes to account for >90% of their body burden. This helps to explain the longer retention of Cs in bottom-dwelling fish near Fukushima.

Declining Mercury Concentrations in Bluefin Tuna Reflect Reduced Emissions to the North Atlantic Ocean.

Tunas are apex predators in marine food webs that can accumulate mercury (Hg) to high concentrations and provide more Hg (∼40%) to the U.S population than any other source. We measured Hg concentrations in 1292 Atlantic bluefin tuna (ABFT, Thunnus thynnus) captured in the Northwest Atlantic from 2004 to 2012. ABFT Hg concentrations and variability increased nonlinearly with length, weight, and age, ranging from 0.25 to 3.15 mg kg-1, and declined significantly at a rate of 0.018 ± 0.003 mg kg-1 per year or 19% over an 8-year period from the 1990s to the early 2000s. Notably, this decrease parallels comparably reduced anthropogenic Hg emission rates in North America and North Atlantic atmospheric Hg0 concentrations during this period, suggesting that recent efforts to decrease atmospheric Hg loading have rapidly propagated up marine food webs to a commercially important species. This is the first evidence to suggest that emission reduction efforts have resulted in lower Hg concentrations in large, long-lived fish.

Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood.

Radioactive isotopes originating from the damaged Fukushima nuclear reactor in Japan following the earthquake and tsunami in March 2011 were found in resident marine animals and in migratory Pacific bluefin tuna (PBFT). Publication of this information resulted in a worldwide response that caused public anxiety and concern, although PBFT captured off California in August 2011 contained activity concentrations below those from naturally occurring radionuclides. To link the radioactivity to possible health impairments, we calculated doses, attributable to the Fukushima-derived and the naturally occurring radionuclides, to both the marine biota and human fish consumers. We showed that doses in all cases were dominated by the naturally occurring alpha-emitter (210)Po and that Fukushima-derived doses were three to four orders of magnitude below (210)Po-derived doses. Doses to marine biota were about two orders of magnitude below the lowest benchmark protection level proposed for ecosystems (10 µGy⋅h(-1)). The additional dose from Fukushima radionuclides to humans consuming tainted PBFT in the United States was calculated to be 0.9 and 4.7 µSv for average consumers and subsistence fishermen, respectively. Such doses are comparable to, or less than, the dose all humans routinely obtain from naturally occurring radionuclides in many food items, medical treatments, air travel, or other background sources. Although uncertainties remain regarding the assessment of cancer risk at low doses of ionizing radiation to humans, the dose received from PBFT consumption by subsistence fishermen can be estimated to result in two additional fatal cancer cases per 10,000,000 similarly exposed people.

Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California.

The Fukushima Dai-ichi release of radionuclides into ocean waters caused significant local and global concern regarding the spread of radioactive material. We report unequivocal evidence that Pacific bluefin tuna, Thunnus orientalis, transported Fukushima-derived radionuclides across the entire North Pacific Ocean. We measured γ-emitting radionuclides in California-caught tunas and found (134)Cs (4.0 ± 1.4 Bq kg(-1)) and elevated (137)Cs (6.3 ± 1.5 Bq kg(-1)) in 15 Pacific bluefin tuna sampled in August 2011. We found no (134)Cs and background concentrations (~1 Bq kg(-1)) of (137)Cs in pre-Fukushima bluefin and post-Fukushima yellowfin tunas, ruling out elevated radiocesium uptake before 2011 or in California waters post-Fukushima. These findings indicate that Pacific bluefin tuna can rapidly transport radionuclides from a point source in Japan to distant ecoregions and demonstrate the importance of migratory animals as transport vectors of radionuclides. Other large, highly migratory marine animals make extensive use of waters around Japan, and these animals may also be transport vectors of Fukushima-derived radionuclides to distant regions of the North and South Pacific Oceans. These results reveal tools to trace migration origin (using the presence of (134)Cs) and potentially migration timing (using (134)Cs:(137)Cs ratios) in highly migratory marine species in the Pacific Ocean.

Fukushima-derived radionuclides in the ocean and biota off Japan.

The Tohoku earthquake and tsunami of March 11, 2011, resulted in unprecedented radioactivity releases from the Fukushima Dai-ichi nuclear power plants to the Northwest Pacific Ocean. Results are presented here from an international study of radionuclide contaminants in surface and subsurface waters, as well as in zooplankton and fish, off Japan in June 2011. A major finding is detection of Fukushima-derived (134)Cs and (137)Cs throughout waters 30-600 km offshore, with the highest activities associated with near-shore eddies and the Kuroshio Current acting as a southern boundary for transport. Fukushima-derived Cs isotopes were also detected in zooplankton and mesopelagic fish, and unique to this study we also find (110 m)Ag in zooplankton. Vertical profiles are used to calculate a total inventory of ~2 PBq (137)Cs in an ocean area of 150,000 km(2). Our results can only be understood in the context of our drifter data and an oceanographic model that shows rapid advection of contaminants further out in the Pacific. Importantly, our data are consistent with higher estimates of the magnitude of Fukushima fallout and direct releases [Stohl et al. (2011) Atmos Chem Phys Discuss 11:28319-28394; Bailly du Bois et al. (2011) J Environ Radioact, 10.1016/j.jenvrad.2011.11.015]. We address risks to public health and marine biota by showing that though Cs isotopes are elevated 10-1,000× over prior levels in waters off Japan, radiation risks due to these radionuclides are below those generally considered harmful to marine animals and human consumers, and even below those from naturally occurring radionuclides.

Reconstructing transoceanic migration patterns of Pacific bluefin tuna using a chemical tracer toolbox.

Large pelagic predators play important roles in oceanic ecosystems, and may migrate vast distances to utilize resources in different marine ecoregions. Understanding movement patterns of migratory marine animals is critical for effective management, but often challenging, due to the cryptic habitat of pelagic migrators and the difficulty of assessing past movements. Chemical tracers can partially circumvent these challenges by reconstructing recent migration patterns. Pacific bluefin tuna (Thunnus orientalis; PBFT) inhabit the western and eastern Pacific Ocean, and are in steep decline due to overfishing. Understanding age-specific eastward transpacific migration patterns can improve management practices, but these migratory dynamics remain largely unquantified. Here, we combine a Fukushima-derived radiotracer (134Cs) with bulk tissue and amino acid stable isotope analyses of PBFT to distinguish recent migrants from residents of the eastern Pacific Ocean. The proportion of recent migrants to residents decreased in older year classes, though the proportion of older PBFT that recently migrated across the Pacific was greater than previous estimates. This novel toolbox of biogeochemical tracers can be applied to any species that crosses the North Pacific Ocean.

Radiocesium in Pacific bluefin tuna Thunnus orientalis in 2012 validates new tracer technique.

The detection of Fukushima-derived radionuclides in Pacific bluefin tuna (PBFT) that crossed the Pacific Ocean to the California Current Large Marine Ecosystem (CCLME) in 2011 presented the potential to use radiocesium as a tracer in highly migratory species. This tracer requires that all western Pacific Ocean emigrants acquire the (134)Cs signal, a radioisotope undetectable in Pacific biota prior to the Fukushima accident in 2011. We tested the efficacy of the radiocesium tracer by measuring (134)Cs and (137)Cs in PBFT (n = 50) caught in the CCLME in 2012, more than a year after the Fukushima accident. All small PBFT (n = 28; recent migrants from Japan) had (134)Cs (0.7 ± 0.2 Bq kg(-1)) and elevated (137)Cs (2.0 ± 0.5 Bq kg(-1)) in their white muscle tissue. Most larger, older fish (n = 22) had no (134)Cs and only background levels of (137)Cs, showing that one year in the CCLME is sufficient for (134)Cs and (137)Cs values in PBFT to reach pre-Fukushima levels. Radiocesium concentrations in 2012 PBFT were less than half those from 2011 and well below safety guidelines for public health. Detection of (134)Cs in all recent migrant PBFT supports the use of radiocesium as a tracer in migratory animals in 2012.

Evolutionary patterns in trace metal (cd and zn) efflux capacity in aquatic organisms.

The ability to eliminate (efflux) metals is a physiological trait that acts as a major driver of bioaccumulation differences among species. This species-specific trait plays a large role in determining the metal loads that species will need to detoxify to persist in chronically contaminated environments and, therefore, contributes significantly to differences in environmental sensitivity among species. To develop a better understanding of how efflux varies within and among taxonomic groupings, we compared Cd and Zn efflux rate constants (ke values) among members of two species-rich aquatic insect families, Ephemerellidae and Hydropsychidae, and discovered that ke values strongly covaried across species. This relationship allowed us to successfully predict Zn efflux from Cd data gathered from aquatic species belonging to other insect orders and families. We then performed a broader, comparative analysis of Cd and Zn ke values from existing data for arthropods, mollusks, annelids, and chordates (77 species total) and found significant phylogenetic patterns. Taxonomic groups exhibited marked variability in ke magnitudes and ranges, suggesting that some groups are more constrained than others in their abilities to eliminate metals. Understanding broader patterns of variability can lead to more rational extrapolations across species and improved protectiveness in water-quality criteria and ecological assessment.

Associations between total mercury, trace minerals, and blood health markers in Northwest Atlantic white sharks (Carcharodon carcharias).

The ecology and life-histories of white sharks make this species susceptible to mercury bioaccumulation; however, the health consequences of mercury exposure are understudied. We measured muscle and plasma total mercury (THg), health markers, and trace minerals in Northwest Atlantic white sharks. THg in muscle tissue averaged 10.0 mg/kg dry weight, while THg in blood plasma averaged 533 µg/L. THg levels in plasma and muscle were positively correlated with shark precaudal length (153-419 cm), and THg was bioaccumulated proportionally in muscle and plasma. Nine sharks had selenium:mercury molar ratios in blood plasma >1.0, indicating that for certain individuals the potential protective effects of the trace mineral were diminished, whereas excess selenium may have protected other individuals. No relationships between plasma THg and any trace minerals or health markers were identified. Thus, we found no evidence of negative effects of Hg bioaccumulation, even in sharks with very high THg.

Risk assessment for seafood consumers exposed to mercury and other trace elements in fish from Long Island, New York, USA.

We determined concentrations of Hg, Pb, Cd, Cr, As, Ni, Ag, Se, Cu, and Zn in muscle tissue of six commonly consumed Long Island fish species (black seabass, bluefish, striped bass, summer flounder, tautog, and weakfish, total sample size = 1211) caught off Long Island, New York in 2018 and 2019. Long-term consumption of these coastal fish could pose health risks largely due to Hg exposure; concentrations of the other trace elements were well below levels considered toxic for humans. By combining the measured Hg concentrations in the fish (means ranging from 0.11 to 0.27 mg/kg among the fish species), the average seafood consumption rate, and the current US EPA Hg reference dose (0.0001 mg/kg/d), it was concluded that seafood consumption should be limited to four fish meals per month for adults for some fish (bluefish, tautog) and half that for young children. Molar ratios of Hg:Se exceeded 1 for some black seabass, bluefish, tautog, and weakfish.