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Blood plasma levels of heavy metals and trace elements in white sharks (Carcharodon carcharias) and potential health consequences
... Plasma THg concentrations were expressed in μg l −1 , as in past studies (e.g. Merly et al. 2019). ...
... Despite this, the current study examined THg concentrations in oceanic whitetip shark plasma and their association with muscle THg levels, mainly to better understand the toxicological relevance of plasma Hg levels in sharks and their relatives. This was motivated by a recent study on plasma heavy metal levels in white sharks, which reported high, potentially toxic plasma THg concentrations in this species (range = 36.0−265.5 μg l −1 , Merly et al. 2019). However, since muscle THg concentrations were not measured by Merly et al. (2019), the toxicological significance of their findings remains uncertain. ...
... This was motivated by a recent study on plasma heavy metal levels in white sharks, which reported high, potentially toxic plasma THg concentrations in this species (range = 36.0−265.5 μg l −1 , Merly et al. 2019). However, since muscle THg concentrations were not measured by Merly et al. (2019), the toxicological significance of their findings remains uncertain. The results of the current study showed that THg concentrations in oceanic whitetip plasma and muscle were significantly correlated, suggesting that plasma Hg concentrations in sharks may at least partly reflect long-term Hg accumulation patterns and the potential for toxicological responses. ...
The oceanic whitetip shark Carcharhinus longimanus is a widely distributed large pelagic shark species once considered abundant in tropical and warm temperate waters, but recently listed as Critically Endangered by the IUCN due to drastic population declines associated with overfishing. In addition to risks posed to its populations due to overexploitation, oceanic whitetip sharks are also capable of accumulating elevated quantities of harmful environmental toxicants, placing them at special risk from anthropogenic pollution. Herein, we provide the first data on accumulation of the toxic, non-essential metal mercury (Hg) in northwest Atlantic (NWA) oceanic whitetip sharks, focusing on aggregations occurring at Cat Island, The Bahamas. Total Hg (THg) concentrations were measured in muscle of 26 oceanic whitetip sharks and compared with animal length and muscle δ ¹⁵ N to evaluate potential drivers of Hg accumulation. THg concentrations were also measured in fin and blood subcomponents (red blood cells and plasma) to determine their value as surrogates for assessing Hg burden. Muscle THg concentrations were among the highest ever reported for a shark species and correlated significantly with animal length, but not muscle δ ¹⁵ N. Fin, red blood cell, and plasma THg concentrations were significantly correlated with muscle THg. Fin THg content was best suited for use as a surrogate for estimating internal Hg burden because of its strong relationship with muscle THg levels, whereas blood THg levels may be better suited for characterizing recent Hg exposure. We conclude that Hg poses health risks to NWA oceanic whitetip sharks and human consumers of this species.
... Currently, the main threats to elasmobranch populations include overfishing, incidental fishing capture (i.e., bycatch) (Mandelman et al. 2013), and habitat destruction (Ellis et al. 2004), with the latter being increasingly exacerbated by pollution and climate change (Ward-Paige et al. 2012). Given that most elasmobranchs are apex or meso predators, many are critically important to the health of their respective aquatic ecosystems (White et al. 2012;Hammerschlag et al. 2019), but also provide significant ecosystem services to countries, in the form of revenue and/or sustenance (e.g., eco-tourism and fisheries) (Hammerschlag and Gallagher 2011;Ward-Paige et al. 2012). ...
... Although maternal transference is occurring for a host of environmental contaminants, there is no definitive understanding as to the effects on adults or offspring. For example, Merly et al. (2019) documented extremely high levels of circulating mercury, arsenic, and cadmium in adult white sharks, but no impact on the body condition was observed. Furthermore, high circulating concentrations of copper were positively associated with body condition, and the authors referenced copper as a co-factor for enzymatic activity with potential to protect against oxidative stress, thereby increasing body condition (Merly et al. 2019). ...
... For example, Merly et al. (2019) documented extremely high levels of circulating mercury, arsenic, and cadmium in adult white sharks, but no impact on the body condition was observed. Furthermore, high circulating concentrations of copper were positively associated with body condition, and the authors referenced copper as a co-factor for enzymatic activity with potential to protect against oxidative stress, thereby increasing body condition (Merly et al. 2019). So, while there is evidence that metals and other toxins are present in adults and transferred via maternal inputs, the effects of such contaminants, particularly on developing elasmobranch embryos, is not yet understood. ...
The consequences of human influence can arise in vertebrates as primary, secondary, or even tertiary stressors and may be especially detrimental for slow growing species with long generation times (i.e., K-selected species). Here, we review the impacts of both direct and indirect human interactions on the reproductive biology of elasmobranchs. Within direct human influence, capture-induced stress from fisheries bycatch and poor coastal management practices leading to habitat destruction and pollution are among the most impactful on elasmobranch reproduction. Capture-induced stress has been shown to negatively influence offspring and reproductive capacity via capture-induced parturition as well as by disrupting the reproductive physiology of adults. Habitat degradation impacts essential ecosystems that are necessary for the development of young elasmobranchs. Pollutants such as heavy metals, legacy pesticides, and flame retardants have been traced through elasmobranch reproduction; however, the long-term effects of these exogenous chemicals are yet to be determined. Furthermore, within indirect human impacts, climate change-mediated influences (e.g., ocean warming and acidification) can impact development, physiological processes, and behavioral patterns necessary for essential tasks such as foraging, growth, reproduction, and ultimately survival. Here, we also present a case study, where data regarding temperature and incubation time from 28 egg-laying elasmobranch species were examined to show relevance of such data in predicting how suitable (e.g., via maximum threshold temperatures) habitats will be for skate and shark development in the coming century. Concomitantly, this information highlights areas for future research that will help inform better management as well as climate change forecasting for this threatened group of aquatic vertebrates.
... About arsenic, it has been observed in some fish that exposure at high levels may cause sublethal (such as oxidative stress, immunotoxicity or enzyme function alteration) to lethal effects (Merly et al., 2019;Bhattacharya and Bhattacharya, 2007). ...
... Generally, most of the mercury is found in organic form, as observed by Li et al. (2023) for the muscles of some sharks which revealed about 100 % of MeHg compared to total mercury. Mercury toxicity is associated with disruption of enzymatic function as it has high tendency to form complexes with sulphur in the cysteine residues of proteins (Merly et al., 2019). Unlike arsenic, the organic form of mercury is the most toxic such as MeHg a potent neurotoxin that is readily accumulated by aquatic biota due to its lipophilic and protein binding properties (Ullrich et al., 2001). ...
This is a first attempt to assess the levels of trace elements, PAHs, and TPHs in six elasmobranch species (Carcharhinus dussumieri, C. sorrah, Chiloscyllium arabicum, Gymnura poecilura, Sphyrna lewini, S. mokarran) from the Arabian Gulf. The chemical analysis showed that the concentrations of contaminants differed significantly between liver and muscle samples with both pelagic and benthic species and all families. For all species, contaminant concentrations were significantly higher in the liver than in the muscle. While muscle contaminant concentrations differed significantly with respect to species' lifestyles and families, those of liver showed no significant differences between pelagic and benthic species, neither between the four families nor between the six species. None of the analysed contaminants exceeded the internationally recognized standards in all studied species. These results enrich the knowledge on the bioaccumulation of contaminants in elasmobranchs and allow to assess the environmental status of the Arabian Gulf.
... Nevertheless, the accumulation of trace elements has a negative effect on the health of elasmobranch species too (Depew et al., 2012;Bezerra et al., 2019;Merly et al., 2019;Tiktak et al., 2020;Wosnick et al., 2021). Few studies have evaluated the effects from the contamination of specific trace elements on elasmobranch species health, highlighting the provoked implications in osmoregulation (e.g. ...
... While Hg has related to alternation in the reproductive biology of the species (Bezerra et al., 2019). However, there are currently no toxic thresholds for tolerable concentrations of metals and other elements in elasmobranchs (Merly et al., 2019), while their impacts on the health and the well-being of elasmobranchs is a poorly known and heavily understudied (Consales and Marsili, 2021). ...
Trace elements have the potential to bioaccumulate in marine organisms and to biomagnify towards the upper levels of marine trophic webs, resulting in a range of negative effects on organisms. Elasmobranchs are highly susceptible to bioaccumulation of trace metals, while their consumption by humans is increasing worldwide. Therefore, it is important to monitor the trace metal content in the edible tissues of elasmobranchs. This work reveals the content of 12 trace metals in the edible tissues of 10 elasmobranch species caught in Greek waters. Levels above the permissible limits for Hg and Pb were found in some species, while analysis of the lifetime consumption risk for adults and children using the Target Hazard Quotient (THQ), revealed a high risk for two of the most toxic substances on the priority list for substances, namely As and Hg. These are preliminary results, and further research is required to understand better the issue.
... Blood metals' level in elasmobranchs was scarcely studied, and reference values were not available in the literature except for the study of Merly and co-authors (Merly et al. 2019) that analysed metal concentrations in the white shark (Carcharodon carcharias) from South Africa. ...
... In the blood of the spotted dogfish, higher levels of almost all the essential elements were found in comparison to the white shark (Merly et al. 2019) that could be related with Fig. 1 a Total metals (mg/kg) and ΣREE (μg/kg) concentrations in spotted dogfish tissues. b Total metals (mg/kg) and ΣREE (μg/kg) concentrations in spotted dogfish water tank and feed Fig. 2 Boxplot of nonessential elements in spotted dogfish (mg/kg) a different species metabolism as well as to the different feeding opportunities (homogeneous diet in housed animal). ...
Metals (trace elements and rare earth elements, REEs) were analysed by inductively coupled plasma-mass spectrometry in blood, the liver, the kidney and muscle of ex situ spotted dogfish (Scyliorhinus stellaris). The controlled environment in which these elasmobranchs were hosted allowed to assess a baseline level of metals in the different organs since exposure via water and food can be easily monitored. The highest arsenic, chromium, copper, and iron values were found in the liver, cobalt in the kidney, and cadmium and rubidium in muscle. The highest total trace elements content was found in the trend liver (75 mg kg⁻¹) > blood (33 mg kg⁻¹) > muscle (31 mg kg⁻¹) > kidney (10 mg kg⁻¹), while the ΣREEs was the liver (30 μg kg⁻¹) > muscle (15 μg kg⁻¹) > kidney (13 μg kg⁻¹) > blood (4.1 μg kg⁻¹). Between REEs, the most represented element was scandium. Significant differences in the concentration of metals among organs were observed for almost all elements. Nonessential elements were generally lower and essential elements higher in the examined specimens compared to wild elasmobranchs, suggesting a close relationship between a balanced diet and animal welfare.
... These calculations are valuable tools to assess potential protective effects of essential elements against the effects of toxic metals and metalloids, where ratios higher than 1 for the former compared to the latter are considered protective . Furthermore, considering the notably high Hg concentrations detected herein and the important relationship between Se and Hg reported in the literature for sharks (Nam et al., 2011;Bergés-Tiznado et al., 2015;Merly et al., 2019), the Se:Hg molar ratio was also calculated, even though no statistically significant correlation between these elements was noted. The calculations indicate a molar ratio of 64:1 for Se:Pb, and a 0.7:1 ratio for Se:Hg. ...
... The Se in high concentrations was not enough to further a protective function to Hg in nurse sharks (molar ratio Se:Hg 0.7), corroborating reports for pelagic species such as the mako shark (Isurus oxyrinchus -molar ratio Se:Hg 0.5) (Kaneko and Ralston, 2007), the blue shark (Prionace glauca -molar ratio Se:Hg 0.3) (Escobar-Sánchez et al., 2011), and the pelagic thresher (Alopias pelagicusmolar ratio Se:Hg 0.2) (Lara et al., 2020). Interestingly, the same was not observed for the lemon shark (Negaprion brevirostris -moral ratio Se:Hg 3.51) (Nam et al., 2011), a large-sized coastal species, and for coastal-pelagic, semi-oceanic sharks, such as the great white shark (Carcharodon carcharias -molar ratio Se:Hg > 1) (Merly et al., 2019), and the scalloped hammerhead (Sphyrna lewini -molar ratio Se:Hg 5.6) (Bergés-Tiznado et al., 2015). Such results indicate that the protective effect of Se to Hg is species-specific rather than habitat-related, as the nurse shark, a coastal benthic shark, lacks the protective effects of Se, as observed for pelagic sharks. ...
It is widely recognized that apex predators, such as large sharks with highly migratory behavior, are particularly vulnerable to pollution, mainly due to biomagnification processes. However, in highly impacted areas, mesopredator sharks with resident behavior can be as vulnerable as apex sharks. In this context, this study evaluated cadmium (Cd), mercury (Hg), lead (Pb), and rubidium (Rb) concentrations, as well as the potentially protective effects of selenium (Se) and the behavior of two non-enzymatic biomarkers, metallothionein (MT) and reduced glutathione (GSH), employing the Atlantic nurse shark Ginglymostoma cirratum as a study model and compared the results with other resident benthic sharks, as well as highly mobile apex sharks. Muscle tissue samples from 28 nurse sharks opportunistically sampled from the Brazilian Amazon Coast were analyzed. Lower metal concentrations were observed for Pb, Rb and Se in the rainy season, while statistically significant correlations between metals were observed only between Hg and Cd and Pb and Se. Molar ratio calculations indicate potential protective Se effects against Pb, but not against Cd and Hg. No associations between MT and the determined metals were observed, indicating a lack of detoxification processes via the MT detoxification route. The same was noted for GSH, indicating no induction of this primary cellular antioxidant defense. Our results indicate that benthic/mesopredator sharks with resident behavior are, in fact, as impacted as highly mobile apex predators, with the traditional detoxification pathways seemingly inefficient for the investigated species. Moreover, considering the studied population and other literature data, pollution should be listed as a threat to the species in future risk assessments.
... Several recent studies also report non-significant relationships between high [THg] in sharks and various health metrics. The authors suggest that the somewhat unique physiology of sharks makes them less sensitive to Hg toxicity (Vélez-Alavez et al. 2013;Merly et al. 2019; Ehnert-Russo and Gelsleichter 2020). Vélez-Alavez et al. (2013), for example, found that while the muscle [THg] of juvenile mako sharks (Isurus oxyrinchus) was elevated, indicators of oxidative stress were lower than expected. ...
... The authors speculated that the sharks had elevated antioxidant defenses that mitigated the typical response seen in studies of reactive oxygen species in response to Hg toxicity. Additionally, when investigating blood plasma levels of Hg in white sharks (Carcharodon carcharias), Merly et al. (2019) concluded that even with high levels of Hg, there was no indication of altered plasma chemistry or impact on overall condition, possibly due to metallothioneins or enzymes binding Hg, thereby reducing its toxicity. Finally, Ehnert-Russo and Gelsleichter (2020) speculated that lifelong neurogenesis in shark brains led to limited neurological impacts despite elevated Hg levels in the brains of Atlantic sharpnose sharks (Rhizoprionodon terraenovae), ...
As apex predators, blacktip sharks (Carcharhinus limbatus) are highly susceptible to biomagnified mercury (Hg) particularly in the Gulf of Mexico (GOM), which is known to contain fishes and invertebrates with elevated Hg levels. Blacktip sharks occur in the GOM year-round and are heavily fished both commercially and recreationally, but little is known about how Hg affects the species. In this study, blood, muscle, liver, and kidney samples were collected from neonatal (n = 57) and juvenile (n = 13) blacktip sharks in Charlotte Harbor, Florida. Hg concentrations in neonates and juveniles were found to be elevated in muscle (mean ± SE = 0.59 ± 0.23 mg kg−1), liver (0.39 ± 0.29 mg kg−1), kidney (0.56 ± 0.25 mg kg−1), and blood (0.059 ± 0.041 mg kg−1) compared to other local shark species and conspecifics from other areas. Blood plasma chemistry, hematology, and liver histology were evaluated to assess the relationship between Hg and tissue damage. Plasma chemistry parameters alanine aminotransferase (ALT) and phosphorus (PHOS) were not correlated with tissue Hg or liver condition index. Hematological effects were also not correlated with tissue Hg. However, melanomacrophage presence and lipid deposition, evaluated as part of histopathological analysis, were found to exhibit a statistically significant association with concentrations of Hg in tissue and ALT levels. These results suggest that Hg exposure potentially had a negative effect on the livers of the blacktip sharks evaluated in the present study.
... historically low commercial value of shark meat, relative demand as a human protein source appears to be a growing global trend 26 . A need to establish baseline concentrations of metals in sharks and their relatives, as well as potential routes of exposure is therefore required 14,17,20 . This is particularly true for developing nations, where less stringent environmental regulations regarding wastewater treatment, anthropogenic emissions, and subsequent management may lead to elevated levels of metals entering coastal waters. ...
... Most metals bioconcentrate and a few biomagnify in marine organisms once they enter the ocean 3,9,10 . Accordingly, long-lived, large-bodied marine predators that exhibit higher trophic positions often display potentially toxic concentrations of metals and other toxicants [11][12][13][14] ,and can therefore be used as environmental sentinels for regional loadings [15][16][17] . As many higher trophic-level marine fishes comprise a proportion of the global seafood demand, a need exists to monitor metal concentrations and evaluate the potential toxicity risk for humans readily consuming fish protein 8,16,17 . ...
Over the last century anthropogenic activities have rapidly increased the influx of metals and metalloids entering the marine environment, which can bioaccumulate and biomagnify in marine top consumers. This may elicit sublethal effects on target organisms and have broad implications for human seafood consumers. We provide the first assessment of metal (Cd, Pb, Cr, Mn, Co, Cu, Zn, As, Ag, and THg) and metalloid (As) concentrations in the muscle tissue of coastal sharks from The Bahamas. A total of 36 individual sharks from six species were evaluated, spanning two regions/study areas, with a focus on the Caribbean reef shark (Carcharhinus perezi), and to a lesser extent the tiger shark (Galeocerdo cuvier), due their high relative abundance and ecological significance throughout coastal Bahamian and regional ecosystems. Caribbean reef sharks exhibited some of the highest metal concentrations compared to five other species, and peaks in the concentrations of Pb, Cr, Cu, Zn, and Ag were observed as individuals reached sexual maturity. Observations were attributed to foraging on larger, more piscivorous prey, high longevity, as well a potential slowing rate of growth. We observed correlations between some metals, which are challenging to interpret but may be attributed to trophic level and ambient metal conditions. Our results provide the first account of metal concentrations in Bahamian sharks, suggesting individuals exhibit high concentrations which may potentially cause sublethal effects. Finally, these findings underscore the potential toxicity of shark meat and have significant implications for human consumers.
... Heavy metals (such as mercury, cadmium, copper, arsenic, chromium, and lead) contamination is problematic in certain geographic areas (Liu et al., 2019;Merly et al., 2019;Safiur Rahman et al., 2019). Therefore, heavy metals should be regularly monitored in fresh and marine ecosystems. ...
... Therefore, heavy metals should be regularly monitored in fresh and marine ecosystems. They can occur at detectable concentrations without affecting the health of aquatic organisms and act as a potential health hazard for marine life and seafood consumers (Merly et al., 2019). The high concentration of such metals disrupts the normal physiological process, causes tissue damage, inhibits growth and reproduction, and modulates early development in aquatic animals including bivalves (Cherkasov et al., 2006;Ghazy et al., 2017;Khan et al., 2018;Saidov and Kosevich, 2019). ...
Bivalve mollusks are important aquatic organisms, which are used for biological monitoring because of their abundance, ubiquitous nature, and abilities to adapt to different environments. MicroRNAs (miRNAs) are small noncoding RNAs, which typically silence the expression of target genes; however, certain miRNAs directly or indirectly upregulate their target genes. They are rapidly modulated and play an essential role in shaping the response of organisms to stresses. Based on the regulatory function and rapid alteration of miRNAs, they could act as biomarkers for biotic and abiotic stress, including environmental stresses and contaminations. Moreover, mollusk, particularly hemocytes, rapidly respond to environmental changes, such as pollution, salinity changes, and desiccation, which makes them an attractive model for this purpose. Thus, bivalve mollusks could be considered a good animal model to examine a system’s response to different environmental conditions and stressors. miRNAs have been reported to adjust the adaptation and physiological functions of bivalves during endogenous and environmental stressors. In this review, we aimed to discuss the potential mechanisms underlying the response of bivalves to stressors and how miRNAs orchestrate this process; however, if necessary, other organisms’ response is included to explain specific processes.
... Moreover, while hepatic demethylation of MeHg is well known in marine mammals (Bolea-Fernandez et al., 2019;Perrot et al., 2016), bony fish do not appear to have such metabolic capacities. Although it has recently been suggested that sharks may have protective mechanisms that mitigate Hg toxicity (Merly et al., 2019), to date there is no evidence of MeHg demethylation in sharks. ...
... High THg concentrations (around 150 mg L À1 ) were found in the blood plasma of South African white sharks Carcharodon carcharias, at levels considered toxic in other vertebrates (Merly et al., 2019). Despite this contamination, no alteration of the body condition nor negative effects on health parameters were observed, suggesting that sharks may have protective mechanisms that mitigate Hg toxicity. ...
... limbatus), blacktip reef (C. melanopterus), nurse (Ginglymostoma cirratum), tiger (Galeocerdo cuvier) and white sharks (Carcharodon carcharias) (Gallagher et al., 2014;Merly et al., 2019;Moorhead et al., 2021;Weideli et al., 2019). However, to date, no comparison between this metric and Fulton's condition factor has been conducted for a species across all life-history stages. ...
Body condition is an important proxy for overall health and energetic status of fishes. The classically-used Fulton's condition factor requires length and mass measurements, but mass can be difficult to obtain in large species. Girth measurements can replace mass for wild pelagic sharks. However, girth-calculated condition has not been validated against Fulton's condition factor intra-specifically, across ontogeny or reproduction, or in a controlled setting. We used the epaulette shark (Hemiscyllium ocellatum), because they are amenable to captive reproduction, to track fine-scale body condition changes across life stages, oviparous reproduction, and between condition indices. We measured four girths, total length, and mass of sixteen captive epaulette sharks across one year and tracked female reproduction daily. We also collected length and mass data from an additional 72 wild-caught sharks and 155 sharks from five previous studies and two public aquaria to examine the relationship between length and mass for this species. Even though data were derived from a variety of sources, a predictable length-mass relationship (R2 = 0.990) was achievable, indicating that combining data from a variety of sources could help overcome knowledge gaps regarding basic life history characteristics. We also found that condition factor decreased during early life stages, then increased again into adulthood, with predictable changes across the female reproductive cycle. Finally, we determined that both Fulton's and girth condition analyses were comparable. Outcomes from this study uniquely provide body condition changes across the complete life history, including fine-scale female reproductive stages and validate the use of girths as a non-lethal whole-organism energetic assessment for fishes. This article is protected by copyright. All rights reserved.
... These pollutants are highly capable of being transported over long distances through the air, rivers, streams and oceans currents (Esposito et al., 2020;Naz et al., 2021;Sparling, 2016;Pirrone et al., 2010). There are studies that report the presence of these pollutants in organisms such as bacteria (Li et al., 2022;Rajeev et al., 2021), plants (Clemens and Ma, 2016;Ö ztürk et al., 2021), invertebrates (Ferreira et al., 2020(Ferreira et al., , 2021, fishes (Martins et al., 2020;Merly et al., 2019;Naz et al., 2021), birds (Pedrobom et al., 2021), mammals (Righetti et al., 2019), and both in eggs and several tissues of adults sea turtles (Miguel et al., 2022;Sinaei and Bolouki, 2017;Ley-Quiñónez et al., 2013) in polluted marine ecosystems. ...
The present study determined the presence of heavy metals in green sea turtles with and without fibropapillomatosis in Itapirubá and Cassino beaches, southern Brazil. The weight, curved length of the carapace and body index were determined and blood was collected to quantify the concentrations of cadmium, lead and mercury. A total of 51 blood samples were analyzed, being 46 positives for at least one of the metals. There was a greater number of juvenile turtles in Itapirubá, larger in size and weight than those in Cassino. No statistical differences were found between metal concentrations between regions or between turtles with and without fibropapillomatosis. There was no significant correlation between metal concentrations, biometric variables and the presence of fibropapilomatose. Metal concentrations were low in both regions, with the highest concentrations being Cd and the lowest Hg.
... For instance, there are numerous types of shark fisheries within South Africa's EEZ (DAFF, 2012;da Silva et al., 2015) as well as off neighbouring countries along the African coastline (Roux and Shannon, 2004). Compounding any direct mortality from captures would be indirect mortality arising from displacement to less optimal areas, prey limitation, and/or environmental stressors such as pollution (da Silva et al., 2015;Hammerschlag et al., 2019;Merely et al., 2019). Finally, the near-disappearance of immature white sharks from Gansbaai since 2017 has been linked to predation risk from transient killer whales (Orcinus orca) (Towner et al., 2022), which raises the possibility that natural mortality rates may also be increasing. ...
It can be difficult to determine whether a prohibition to exploitation ensures effective conservation or recovery for species that remain exposed to fishing effort and other sources of mortality throughout their range. Here we used simulation modeling of four life history scenarios (different productivity and population size) to contextualize potential population response to multiple levels of mortality, using white sharks (Carcharodon carcharias) in South Africa as a case study. The species has been protected since 1991, yet substantial uncertainty about population dynamics persists and recent declines at two aggregation sites have renewed conservation concern. All scenarios indicated that annual removals in the 10s of individuals would substantially limit the potential for and magnitude of any abundance increase following prohibition. Because average known removals from the KwaZulu-Natal Sharks Board's Bather Protection Program have typically remained higher than these thresholds, they likely eliminated much of the conservation benefit derived from prohibition. The only life history scenario to achieve appreciable increase when simulated removals were similar to published averages assumed maturation occurred at a much younger age than currently understood. Our results demonstrate why general application of life history-based simulations can provide a useful mechanism to evaluate the biological plausibility of life history information and abundance trends, and to explore the scope for population response to recovery actions. For South Africa, our results suggest that even known levels of white shark removals, which likely underestimate total removals within their range, may be sufficient to drive abundance decline and new mitigation measures may be required to ensure population recovery.
... Sharks are highly vulnerable to contaminant accumulation during their lifetime due to their longevity, low metabolic rate, high trophic position, and large lipid-enriched livers (Gelsleichter and Walker, 2010;Mull et al., 2012). In sharks, diet is considered the major pathway of the entrance of pollutants, which are later absorbed into the blood and distributed into various organs (Merly et al., 2019). Trace metal concentrations differ among species or populations because they largely depend on prey preferences (McMeans et al., 2007;Lee et al., 2015). ...
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.
... Several studies have been carried out to investigate the impact of trace elements on these organisms. Some research suggests that sharks may have protective mechanisms that mitigate harmful effects of trace metal exposure [67]; other authors propose some interesting associations between biochemical parameters and persistent organic pollutants and metal accumulation levels. Lipid peroxidation and DNA damage may be the main consequences of certain types of contaminants, along with the inhibition of glutathione peroxidase activity [64]. ...
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.
... algal biomass is recognized by the ability to adsorb and absorb elements as heavy and trace metals, e.g., the metalloid arsenic, cadmium, copper, mercury, zinc and other potentially toxic elements. These elements can accumulate in organisms, with effect to populational health and dynamic disruption; especially, mercury deserves attention by the effect of biomagnification, when the metal is transferred by trophic chain and impacts the higher levels of predators, as sharks and marine mammals (Souza-Araujo et al. 2020; Merly et al. 2019). These well recognized potentially toxic elements associated with the emergent properties of other contaminants, as recently observed in microplastic impacts, can interact with the poisoning effect of ADE. ...
Marine pollution caused a growing trend of aesthetic and functional disturbances in coastal ecosystems with environmental, social and economic impairment, with abrupt acceleration in the 1970s. Within these last 50 years, the over-enrichment of continental runoff by nutrients has emerged as one of the leading causes of water quality impairment, with tremendous losses for ecosystem services, the foundations to sustain the fishery, aquaculture, recreation and tourism. Most of these scenarios are anthropogenically driven eutrophication (ADE). Algal blooms and oxygen depletion are among the symptoms of a problem that characterizes the anthropocene together with other global stressors. Worldwide, one of the most iconic cases of ADE on beaches is the green tides of Ulva spp., such as those occurred in Qingdao beach, China, in 2008 and the most recent Sargassum bloom in central tropical Atlantic, with floating material observed for 8000 km, from Africa to Central America, highlighting the problem to the global audience. In this chapter, we present the magnitude of ocean eutrophication, their causes and consequences to human beings and marine biodiversity, and potential solutions to increase the resilience of marine environments and coastal communities.
... The study found that melanomacrophage presence and lipid deposition exhibit a significant association with Hg concentrations, suggesting that Hg exposure may lead to potentially negative effects to blacktip liver. In contrast, an evaluation of plasma levels for 14 heavy metals and 12 trace elements in white sharks, Carcharodon carcharias, did not find any negative effects of metal concentrations upon the determined shark health parameters, including total leukocytes, granulocyte to lymphocyte ratios, and shark body condition (Merly et al., 2019). Taken together, these studies suggest that the sublethal effects of metal concentrations on shark health are likely to depend on the species, life-stage, type and concentration of the accumulated metals, tissue type and associated physiological processes. ...
Contamination by metals is among the most pervasive anthropogenic threats to the environment. Despite the ecological importance of marine apex predators, the potential negative impacts of metal bioaccumulation and biomagnification on the health of higher trophic level species remains unclear. To date, most toxicology studies in sharks have focused on measuring metal concentrations in muscle tissues associating human consumption and food safety, without further investigating potential impacts on shark health. To help address this knowledge gap, the present study evaluated metal concentrations in the gills, muscle, liver, and rectal gland of coastal sharks opportunistically sampled from Brazilian waters and tested for potential relationships between metal bio-accumulation and general shark health and homeostatic balance metrics. Results revealed high metal concentrations in all four tissue types, with levels varying in relation to size, sex, and life-stage. Metal concentrations were also associated with serum biomarkers (urea, lactate, ALT, triglycerides, alkaline phosphatase, and phosphorus) and body condition, suggesting potential negative impacts on organismal health.
... Conversely, fishes such as C. orqueta (1.1% IRI) and fishes from the Gerreaide family (1.6% IRI) had As levels between 1.5 and 2.1 mg kg −1 , respectively. In this study, as well as in previous studies regarding other shark species (Merly et al. 2019), it was assumed that the main As intake by juveniles of S. lewini depends on its feeding habits. Fishes from the Clupeidae family generally have small bodies (10-20 cm TL), feed mostly on small planktonic animals, and are one of the most important families of commercial fishes; they are processed for food, oil, or fish food (Fisher et al. 1995). ...
The bioaccumulation of arsenic (As) in the muscle, liver, kidneys, and brain of the shark Sphyrna lewini was measured in 40 juvenile specimens from southeast Gulf of California. Additionally, the biomagnification factor was calculated through prey items from stomach contents of the analyzed specimens. The concentrations of As (mg kg⁻¹, wet weight) were higher in the muscle (10.1 ± 0.3) and liver (9.4 ± 0.5) than in the brain (4.5 ± 0.3) and kidneys (4.2 ± 0.2), which may be attributed to the biological functions of each tissue. Positive correlations were found between the levels of As in muscle and liver with the biological parameters of S. lewini. Hammerhead sharks feed mainly of teleost fishes with low As values (Clupeidae fishes, 1.1 ± 0.5; Sciaenidae fishes, 1.0 ± 0.6; Scomber japonicus, 1.2 ± 0.6; and Etropus crossotus 2.1 ± 0.4) compared with the predator, indicating biomagnification. Inorganic arsenic (Asi) in muscle was estimated as 3% of the total As, although muscle consumption is unlikely to represent a risk (HQ < 1) in humans. Moreover, the probabilities of developing cancer were estimated as low (3.99 × 10–5 to 3.32 × 10–6). To avoid health risks related to As, a weekly ration must not exceed 69.3 and 484.8 g in children and adults, respectively.
... Marine predators, including many shark species, are relatively sensitive to human-induced environmental degradation because of their large body size, relatively low metabolic rate and slow population growth (Cortés, 2000;Conrath and Musick, 2012;Gallagher et al., 2012). As high-level consumers, they tend to bioaccumulate and biomagnify contaminants (e.g., Hammerschlag et al., 2016;Merly et al., 2019), which can affect several physiological processes, which can result in feminization (Kidd et al., 2007), infertility (Gelsleichter et al., 2005), and behavioral alterations (e.g. increasing feeding rate) (Brodin et al., 2014). ...
The field of marine urban ecology is a nascent, but growing area of research. An understanding of how urbanization may alter the diets and nutrition of marine species living in urbanized coastal habitats is limited. In the present study, we investigated the influence of urbanization on dietary patterns and nutritional quality of the nurse shark Ginglymostoma cirratum, a coastal epibenthic mesopredator. We tested the hypothesis that sharks sampled in urbanized areas (hereafter, ‘urban sharks’) would exhibit lower nutritional quality than individuals sampled in adjacent, but more pristine areas (hereafter ‘non-urban sharks’). To accomplish this, we compared plasma fatty acid profiles of juvenile nurse sharks in proximity to Miami, a large coastal city, within Biscayne Bay, Florida. Results revealed that urban sharks contained higher levels of plasma saturated and bacterial fatty acids compared to non-urban sharks. Urban sharks also exhibited lower proportions of essential fatty acids (i.e., highly unsaturated fatty acids, HUFAs), mainly due to low contributions of omega-6 HUFAs. These results suggest that urban sharks consumed lower-quality food resources than conspecifics in less impacted areas. The apparent poor nutritional quality of prey consumed by shark living in urban areas may have several long-term consequences on their health and growth.
... A lack of differential organ evaluations is also noted, with liver as the most frequently investigated organ, probably due to the fact that MT are known to be highly expressed in this organ, which is the main detoxifying organ of the body (Langston et al., 2002;Ploetz, Fitts & Rice, 2007;Hauser-Davis et al., 2012). In this regard, it is noteworthy that no studies have been carried out in the brain, which could be interesting regarding neurotoxic metals such as Hg and Pb (Merly et al., 2019). In addition, gonad assessments are paramount concerning deleterious reproductive metal effects (Lopes et al., 2019;Hauser-Davis et al., 2020), as several metals have been reported as causing negative reproduction effects in fish, that is, altering sperm motility, and decreasing hormone secretions (Popek et al., 2006;Ebrahimi & Taherianfard, 2011), but were observed in only one assessment herein, on male testes. ...
Elasmobranchs are particularly vulnerable to environmental contamination, especially pollutants that may bioaccumulate and biomagnify, throughout the trophic web, such as metals. However, Elasmobranch management and conservation plans are challenging, and this group is often neglected regarding ecotoxicological analyses, particularly concerning metal detoxification mechanisms. This article discusses metallothionein (MT) mediated metal detoxification in Elasmobranchs and reflects on the current knowledge gap in this regard.
... One recent study indicated that white sharks (Carcharodon carcharias) did not exhibit physiological responses (i.e. no change in enzymatic conditions and leukocyte counts) that would usually be expected when organisms are exposed to high concentrations of heavy metals (Merly et al., 2019). This suggests that some species may be more tolerant to pollutant exposure or are able to biotransform and eliminate organic pollutants (e.g. ...
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.
... They also enter humans through the food chain [2]. For an environmentally friendly assessment of contamination, tissues such as blood plasma of fish [3], frog skin by biopsy [4], lizard single gonadectomy [5], bird fece [6] and feather [7] may be useful. Among invertebrates, the aquatic insects are key biotransporters of contaminants between aquatic and terrestrial ecosystems [8,9]. ...
We tested the usefulness of exuviae as an environmentally friendly method for exploring the variability of the trace element contents of protected insect populations without killing specimens. It is a notable characteristic of dragonflies that they are good ecological indicators for both aquatic and terrestrial habitat quality. Thus, we investigated the trace element accumulation in different stages of dragonflies: larva, exuvia, and adult. Using microwave plasma atomic emission spectrometry (MP-AES), we analysed the concentrations of Al, Ba, Cr, Cu, Fe, Mn, Pb, Sr and Zn. We found that the trace element contents of exuviae are a good proxy of the trace element contents of both the larvae and the adults. We conclude that exuvia is useful for assessing the environmental health of aquatic ecosystems. It is an environmentally friendly method and it can be used even in the case of protected dragonfly species.
... Biomagnification is especially a concern with long-lived predatory marine fishes that people consumed as food, such as swordfish (Xiphias gladius, LC), marlins, sharks, and some tunas and sea basses. For example, mercury (emitted mainly during fossil fuel use), lead, and arsenic have bioaccumulated so much in sharks off South Africa that many species are now considered unsafe for human consumption (McKinney et al., 2016;Bosch et al., 2016;Merly et al., 2019). Recent studies also found unsafe levels of mercury in freshwater fish from regions as wide as Central Africa's Great Lakes (Campbell et al., 2008), Ethiopia's Lake Awassa (Desta et al., 2006), and several reservoirs in West Africa (Quédraogo and Amyot, 2013). ...
Sharks are particularly susceptible to bioaccumulation due to their life history characteristics and trophic position within marine ecosystems. Despite this, studies of bioaccumulation cover only a small proportion of extant species. In this study we report concentrations of trace elements and heavy metals in blood samples of S. lewini for the first time. We report high concentrations of several trace elements and heavy metals, with concentrations of some elements exceeding the limit determined safe for human consumption. High elemental concentrations may reflect biochemical differences between blood plasma and other tissues; however, they may also be symptomatic of high levels of exposure triggered by anthropogenic activities. We also provide evidence of elemental accumulation through ontogeny, the nature of which differs from that previously reported. Ultimately, this baseline study increases our understanding of interspecific and intraspecific variation in bioaccumulation and ecotoxicology in elasmobranchs which may prove important in ensuring adequate management.
Bioindicator species are increasingly valuable in environmental pollution monitoring, and elasmobranch species include many suitable candidates for that role. By measuring contaminants and employing biomarkers of effect in relevant elasmobranch species, scientists may gain important insights about the impacts of pollution in marine ecosystems. This review compiles biomarkers applied in elasmobranchs to assess the effect of pollutants (e.g., metals, persistent organic pollutants, and plastics), and the environmental changes induced by anthropogenic activities (e.g., shifts in marine temperature, pH, and oxygenation). Over 30 biomarkers measured in more than 12 species were examined, including biotransformation biomarkers (e.g., cytochrome P450 1A), oxidative stress-related biomarkers (e.g., superoxide anion, lipid peroxidation, catalase, and vitamins), stress proteins (e.g., heat shock protein 70), reproductive and endocrine biomarkers (e.g., vitellogenin), osmoregulation biomarkers (e.g., trimethylamine N-oxide, Na⁺/K⁺-ATPase, and plasma ions), energetic and neurotoxic biomarkers (e.g., lactate dehydrogenase, lactate, and cholinesterases), and histopathological and morphologic biomarkers (e.g., tissue lesions and gross indices).
Human activities have increased the global circulation of mercury, a potent neurotoxin. Mercury can be converted into methylmercury, which biomagnifies along aquatic food chains and leads to high exposure in fish-eating populations. Here we quantify temporal trends in the ocean-to-land transport of total mercury and methylmercury from fisheries and we estimate potential human mercury intake through fish consumption in 175 countries. Mercury export from the ocean increased over time as a function of fishing pressure, especially on upper-trophic-level organisms. In 2014, over 13 metric tonnes of mercury were exported from the ocean. Asian countries were important contributors of mercury export in the last decades and the western Pacific Ocean was identified as the main source. Estimates of per capita mercury exposure through fish consumption showed that populations in 38% of the 175 countries assessed, mainly insular and developing nations, were exposed to doses of methylmercury above governmental thresholds. Our study shows temporal trends and spatial patterns of Hg transport by fisheries. Given the high mercury intake through seafood consumption observed in several understudied yet vulnerable coastal communities, we recommend a comprehensive assessment of the health exposure risk of those populations.
Predators can impact ecosystems through consumptive or risk effects on prey. Physiologically, risk effects can be mediated by energetic mechanisms or stress responses. The predation-stress hypothesis predicts that risk induces stress in prey, which can affect survival and reproduction. However, empirical support for this hypothesis is both mixed and limited, and the conditions that cause predation risk to induce stress responses in some cases, but not others, remain unclear. Unusually clear-cut variation in exposure of Cape fur seals (Arctocephalus pusillus pusillus) to predation risk from white sharks (Carcharodon carcharias) in the waters of Southwestern Africa provides an opportunity to test the predation-stress hypothesis in the wild. Here, we measured fecal glucocorticoid concentrations (fGCM) from Cape fur seals at six discrete islands colonies exposed to spatiotemporal variation in predation risk from white sharks over a period of three years. We found highly elevated fGCM concentrations in seals at colonies exposed to high levels of unpredictable and relatively uncontrollable risk of shark attack, but not at colonies where seals were either not exposed to shark predation or could proactively mitigate their risk through antipredatory behavior. Differences in measured fGCM levels were consistent with patterns of risk at the site and seasonal level, for both seal adults and juveniles. Seal fGCM levels were not correlated with colony population size, density, and geographic location. Investigation at a high risk site (False Bay) also revealed strong correlations between fGCM levels and temporal variation in shark attack rates, but not with shark relative abundance. Our results suggest that predation risk will induce a stress response when risk cannot be predicted and/or proactively mitigated by behavioral responses.
Introduction: There is increasing evidence that the pathophysiological target of mercury is in fact selenium, rather than the covalent binding of mercury to sulfur in the body’s ubiquitous sulfhydryl groups. The role of selenium in mercury poisoning is multifaceted, bidirectional, and central to understanding the target organ toxicity of mercury.
Methods: An initial search was performed using Medline/PubMed, Toxline, Google Scholar, and Google for published work on mercury and selenium. These searches yielded 2018 citations. Publications that did not evaluate selenium status or evaluated environmental status (e.g., lake or ocean sediment) were excluded, leaving approximately 500 citations. This initial selection was scrutinized carefully and 117 of the most relevant and representative references were selected for use in this review.
Binding of mercury to thiol/sulfhydryl groups: Mercury has a lower affinity for thiol groups and higher affinity for selenium containing groups by several orders of magnitude, allowing for binding in a multifaceted way. The established binding of mercury to thiol moieties appears to primarily involve the transport across membranes, tissue distribution, and enhanced excretion, but does not explain the oxidative stress, calcium dyshomeostasis, or specific organ injury seen with mercury.
Effects of mercury on selenium and the role this plays in the pathophysiology of mercury toxicity: Mercury impairs control of intracellular redox homeostasis with subsequent increased intracellular oxidative stress. Recent work has provided convincing evidence that the primary cellular targets are the selenoproteins of the thioredoxin system (thioredoxin reductase 1 and thioredoxin reductase 2) and the glutathione-glutaredoxin system (glutathione peroxidase). Mercury binds to the selenium site on these proteins and permanently inhibits their function, disrupting the intracellular redox environment. A number of other important possible target selenoproteins have been identified, including selenoprotein P, K, and T. Impairment of the thioredoxin and glutaredoxin systems allows for proliferation intracellular reactive oxygen species which leads to glutamate excitosis, calcium dyshomeostasis, mitochondrial injury/loss, lipid peroxidation, impairment of protein repair, and apoptosis. Methylmercury is a more potent inhibitor of the thioredoxin system, partially explaining its increased neurotoxicity. A second important mechanism is due to the high affinity of mercury for selenium and the subsequent depletion of selenium stores needed for insertion into de novo generation of replacement selenoproteins. This mercury-induced selenium deficiency state inhibits regeneration of the selenoproteins to restore the cellular redox environment.
The effects of selenium on mercury and the role this plays in biological response to mercury: Early research suggested selenium may provide a protective role in mercury poisoning, and with limitations this is true. The roles selenium plays in this reduction of mercury toxicity partially depends on the form of mercury and may be multifaceted including: 1) facilitating demethylation of organic mercury to inorganic mercury; 2) redistribution of mercury to less sensitive target organs; 3) binding to inorganic mercury and forming an insoluble, stable and inert Hg:Se complex; 4) reduction of mercury absorption from the GI tract; 5) repletion of selenium stores (reverse selenium deficiency); and 6) restoration of target selenoprotein activity and restoring the intracellular redox environment. There is conflicting evidence as to whether selenium increases or hinders mercury elimination, but increased mercury elimination does not appear to be a major role of selenium. Selenium supplementation has been shown to restore selenoprotein function and reduce the toxicity of mercury, with several significant limitations including: the form of mercury (methylmercury toxicity is less responsive to amelioration) and mercury dose.
Conclusions: The interaction with selenium is a central feature in mercury toxicity. This interaction is complex depending on a number of features such as the form of mercury, the form of selenium, the organ and dose. The previously suggested “protective effect” of selenium against mercury toxicity may in fact be backwards. The effect of mercury is to produce a selenium deficiency state and a direct inhibition of selenium’s role in controlling the intracellular redox environment in organisms. Selenium supplementation, with limitations, may have a beneficial role in restoring adequate selenium status from the deficiency state and mitigating the toxicity of mercury.
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.
The present study evaluates the relation between
chronic arsenic (As) exposure in the natural distribution
area of wild brown trout (Salmo trutta), oxidative stress and
antioxidant enzymatic defenses. Two rivers of the same
watershed were evaluated to highlight the correlation
between As accumulation and the resulting stress: (i) the
Presa River, which has high chronic As levels (2281.66 μg/L)
due to past mining activity, and (ii) the Bravona River
(control river). This metalloid was measured in main fish
tissues (gills, kidney, liver, muscle, gonads and fins) and
water. As organotropism in S. trutta was kidney > liver >
gill > fin > gonad > muscle. The HepatoSomatic Index
(HSI) and somatic condition (CF) were used to compare fish
population conditions from both sites. Arsenic can be
absorbed by the gills and can induce oxidative stress and
disturb antioxidant defenses. The aim of this study was to
evaluate oxidative stress response by measuring malondialdehyde
(MDA) content, as a marker of lipid peroxidation,
and antioxidant enzymatic defenses (Superoxide
dismutase (SOD), catalase CAT, glutathione peroxidase
(GPx) and glutathione S-transferase (GST)), in the main
tissues of control and exposed trout. The highest MDA
content was found in the kidney and liver of exposed trout.
SOD and CAT activities in exposed livers and kidneys were
considerably increased while a significant rise of GPx
activity was observed only in the liver. GST activity was
found to be significantly induced in the liver of exposed
trout. The results demonstrate that arsenic bioaccumulation
can induce lipid peroxidation and substantial modifications
in antioxidant enzymatic defenses in main wild trout tissues.
The concentrations of metals in intertidal water and surface sediment were measured at Scarborough, Hout Bay, Green Point, Milnerton and Bloubergstrand in Cape Town, South Africa, between Autumn 2010 and Autumn 2011. In terms of Pollution Load Index (PLI) of metals in the sediment, the sites were ranked in the following order: Bloubergstrand > Hout Bay > Green Point > Milnerton > Scarborough. Seasonally, metal loads were highest in Autumn 2011 and lowest in Autumn 2010. The higher metal concentrations reported in sediment suggested that both localised anthropogenic and natural weathering were the sources of metals recorded. Surprisingly, metal concentrations were similar to those reported in 1985 for the same sites, suggesting that the intertidal environment in Cape Town has not been increasingly contaminated with metals. The findings provide a baseline of metal concentrations that can be used for further research in the region.
Sharks have greater risk for bioaccumulation of marine toxins and mercury (Hg), because they are long-lived predators. Shark fins and cartilage also contain β-N-methylamino-l-alanine (BMAA), a ubiquitous cyanobacterial toxin linked to neurodegenerative diseases. Today, a significant number of shark species have found their way onto the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Many species of large sharks are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products. Recent studies suggest that the consumption of shark parts may be a route to human exposure of marine toxins. Here, we investigated BMAA and Hg concentrations in fins and muscles sampled in ten species of sharks from the South Atlantic and Pacific Oceans. BMAA was detected in all shark species with only seven of the 55 samples analyzed testing below the limit of detection of the assay. Hg concentrations measured in fins and muscle samples from the 10 species ranged from 0.05 to 13.23 ng/mg. These analytical test results suggest restricting human consumption of shark meat and fins due to the high frequency and co-occurrence of two synergistic environmental neurotoxic compounds.
Concentrations of 11 trace elements in three tissues of
porbeagle shark Lamna nasus (n = 33) were determined. The maximum
observed concentrations of Cd and Pb in muscle were 0.04 and 0.01 mg kg-
1, respectively, and all muscle samples were below European seafood
limits for these metals. Hg concentrations in either the red or white
muscle that exceeded European regulations for seafood were observed in
one-third of specimens. Hg concentration, however, increased with length,
and all fish >195 cm had concentrations >1.0 mg kg-1, with a maximum
observed value of 2.0 mg kg-1. Concentrations of Fe and Cu were, on
average, 9.7 and 10 times higher in red muscle than in nearby white
muscle, respectively. Mn, Zn, As and Se were also found in significantly
higher concentrations in red muscle than in white muscle.
The impact of sublethal toxicity of sodium arsenite on hematological and certain biochemical parameters of the fresh water catfish Clarias batrachus has been analysed following exposure of sublethal concentration (1mg/L; 5% of LC50 value) of sodium arsenite for 10, 30, 45, and 60 days. Arsenic bioaccumulation in the blood tissue of the fish increased progressively with increased period of exposure. The values of total erythrocyte count (TECs), total leucocytes count (TLCs), hemoglobin concentration, and packed cell volume (PCV) 1.40±0.03×106/mm3, 174.83±2.74×103/mm3, 5.01±0.26g/100ml, 25.00±1.06 were observed respectively at the end of 60 days of exposure. The results of hematological indices were found to be 179.23±8.81fl/cell for mean corpuscular volume (MCV), 35.92±1.89pg/cell for mean corpuscular hemoglobin (MCH) and 20.17±1.12g/dl for mean corpuscular hemoglobin concentration (MCHC). The present findings are clearly indicating severe fish anemia due to the arsenic salt exposure. The continued arsenic toxicity results in decreased serum protein concentration that might be a cause for the loss of weight as well as weakness in the fish.
Refugia play an important role in shaping predator/prey interactions; however, few studies have investigated predator–prey relationships between large marine vertebrates, mainly due to the logistical challenges of studying marine species. The predictable interactions between Cape fur seals and white sharks in South Africa at two neighbouring seal colonies (Seal Island and Geyser Rock) with similar breeding conditions, but distinct adjacent seascapes, offer an opportunity to address this gap. Geyser Rock differs from Seal Island in being surrounded by abundant refugia in the form of kelp beds and shallow reefs, while Seal Island is mostly surrounded by deep open water. In this study, we compare data collected from Geyser Rock to the published data at Seal Island and ask, do seals adjust their anti-predator tactics as a function of landscape features? We found that during periods of high white shark presence, seals at Geyser Rock reduced their presence in open-water and utilized areas that contained complex landscapes around the colony. Although seals at Geyser Rock formed groups when traversing open water, neither group size (high risk median = 4, low risk median = 5) nor temporal movement patterns varied significantly with white shark presence as has been shown at Seal Island. Furthermore, recorded hourly predation rates at Seal Island were 12.5 times higher than at Geyser Rock. Together, these findings suggest that refuge use may be the more effective anti-predator response of seals to a seasonally abundant predator and that the predations at Seal Island reflect a comparative lack of refugia.
Iron deficiency is the most prevalent nutritional deficiency, affecting more than 30% of the total world's population. It is a major public health problem in many countries around the world. Over the years various methods have been used with an effort to try and control iron-deficiency anemia. However, there has only been a marginal reduction in the global prevalence of anemia. Why is this so? Iron and zinc are essential trace elements for humans. These metals influence the transport and absorption of one another across the enterocytes and hepatocytes, due to similar ionic properties. This paper describes the structure and roles of major iron and zinc transport proteins, clarifies iron-zinc interactions at these sites, and provides a model for the mechanism of these interactions both at the local and systemic level. This review provides evidence that much of the massive extent of iron deficiency anemia in the world may be due to an underlying deficiency of zinc. It explains the reasons for predominance of cellular zinc status in determination of iron/zinc interactions and for the first time thoroughly explains mechanisms by which zinc brings about these changes.
Selenium (Se) is an essential trace element for humans. It is found in the enzyme glutathione peroxidase. This enzyme protects the organism against certain types of damage. Some data suggest that Se plays a role in the body's metabolism of mercury (Hg). Selenium has in some studies been found to reduce the toxicity of Hg salts. Selenium and Hg bind in the body to each other. It is not totally clear what impact the amount of Se has in the human body on the metabolism and toxicity of prolonged Hg exposure.
Behavioral ecologists might often benefit by the ability to directly measure an animal's body condition as an estimate of foraging success, and ultimately fitness. Here we compare the reliability and effectiveness of three indices of body condition that have been heavily used in the morphometrics literature. We examined the ratio index (body mass/body size), the slope-adjusted ratio index (based on regression slopes generated from a reference population), and the residual index (the residuals of a regression of body mass on body size). We present the results of tests performed in the field and laboratory on two ecologically and evolutionarily divergent spider species: the vagrant wolf spider Pardosa milvina (Araneae, Lycosidae), and the colonial orb-weaver Metepeira incrassata (Araneae, Araneidae). The ratio index correlated with body size, which weakened the strength of conclusions that could be drawn. The slope-adjusted ratio index requires an independent and large data set with which to generate the expected values, and was likewise sensitive to body size. The residual index, with appropriate transformations to achieve homoscedasticity, was the most reliable index because it did not vary with body size, and we recommend its general use in behavioral studies that require a condition estimate.
The documents on Metallothioneins (MTs) in aquatic creatures, especially focusing on their function as biomarkers in environmental monitoring programmes, are vast and increasing. There are, however, few papers to summary the physiological role of MTs in aquatic organisms especially on development. The multifaceted roles of MTs include involvement in homeostasis, protection against heavy metals and oxidant damages, and metabolic regulation, sequestration and/or redox control. In this paper, we have collected published information on MTs in aquatic organisms—pisces, amphibians, mammals etc, and analyzed their function in these aquatic animals. MTs have four main functions in aquatic vertebrate. They are respectively bioaccumulation of toxic metals and detoxification, homeostatic regulation of metals, protection against oxidative stress and neuroprotective mechanism. MTs separate in different tissues and they have various distributions in different tissues of aquatic vertebrate, including liver, gills, kidney, testes and brain. MTs can be induced by a variety of environmental and physiological factors, among which, heavy metals are the main kind of MTs inducers in aquatic vertebrate. Here we pay more attention on the essential metals copper (Cu) and zinc (Zn) and the non-essential metals cadmium (Cd), silver (Ag), lead (Pb) and mercury (Hg).
Marine elasmobranchs maintain their body fluid isoosmotic or slightly hyperosmotic to the exter-nal medium by the retention of large urea con-centrations. This review focuses on the strate-gies adopted by these fishes to maintain a large outwardly direct concentration gradient of this osmolyte minimizing the loss across the main interfaces between body fluid and the external medium such as the gills, the kidney and the rectal gland, thus reducing the cost of making urea. The high plasma osmolarity, mainly main-tained by urea retention, is a challenge to vol-ume homeostasis when fish move from sea-water to water with a low salinity, since the high water permeability of branchial epithelium would cause a net flux of water into the animal. Since the renal regulation of urea retention in habitat with different salinities is crucial for the osmotic homeostasis of these species, the regulation of the activity and/or the expression of urea trans-porters in renal tubules will be also discussed. In addition attention will be paid on the urea– methylamine system involved in maintaining the stability and functioning of many proteins since it is known that the high urea concentration found in marine elasmobranch fish, similar only to that found in mammalian kidney, has a desta-bilizing effect on many macromolecules and inhibits functions such as ligand binding.
Arsenic toxicity is a worldwide health concern as several millions of people are exposed to this toxicant via drinking water, and exposure affects almost every organ system in the body including the brain. Recent studies have shown that even low concentrations of arsenic impair neurological function, particularly in children. This review will focus on the current epidemiological evidence of arsenic neurotoxicity in children and adults, with emphasis on cognitive dysfunction, including learning and memory deficits and mood disorders. We provide a cohesive synthesis of the animal studies that have focused on neural mechanisms of dysfunction after arsenic exposure including altered epigenetics; hippocampal function; glucocorticoid and hypothalamus-pituitary-adrenal axis (HPA) pathway signaling; glutamatergic, cholinergic and monoaminergic signaling; adult neurogenesis; and increased Alzheimer’s-associated pathologies. Finally, we briefly discuss new studies focusing on therapeutic strategies to combat arsenic toxicity including the use of selenium and zinc.
The aim of present study was to evaluate whether short-term exposures to high concentrations of heavy metals may induce stress symptoms in fish blood. Common carp were subjected for 3 hours to 10, 5, 10 or 20 mg/l of lead, copper, cadmium or zinc, respectively, and subsequently transferred to clean water. Blood was sampled immediately after the end of exposures, and then daily until 96 hours post exposures. In red blood cell system transient changes were observed such as an increase in hematocrit value without a substantial changes in red blood cell count (which indicates swelling of the cells), and an increase in erythropoietic rate (indicated by an increase in percentage of immature cells in circulation). In the white blood cell system – a decrease in total leukocyte count took place caused by a considerable drop in lymphocyte count. In some cases (particularly in Pb and Cd-intoxicated fish) percentage of neutrophils increased. However, metal exposures (Cd, Zn) resulted in a reduced ability of intracellular killing by these cells (a decrease in reactive oxygen radical production). The changes gradually developed with time after the end of exposure, and no recovery was observed until 96 hours from transfer of fish to clean water. The obtained data show that a short-term exposures to high levels heavy metals induced stress reactions in fish. In the red blood cell system adaptive changes prevailed, preparing the organism to an increased energy expense, while the changes observed in the white blood cell system indicate a considerable immunosuppressive effect of stress. Therefore, even a short-term exposure to heavy metals induces a persistent stress in fish which may render them more susceptible to diseases.
Salmon is a kind of fish which has good nutrition for human but it can be contaminated by heavy metal such as arsenic. In risk assessment , the provisional tolerable weekly intake (PTWI) for inorganic arsenic is 15 μg/kg b.w./week and the organic forms of arsenic present in sea foods need different consideration from the inorganic arsenic in water. There are no reports of toxicity in man or animals from the consumption of organoarsenicals in seafood. Organic arsenic compounds such as arsenobetaine and arsenocholine seem not to be converted to inorganic arsenic in vivo and not genotoxic in mammalian cells in vitro. Therefore, arsenobetaine and arsenocholine from fish and sea food consumption is not considered to represent a significant health risk.
In studies of animal ecology, it is fashionable to use the residuals from an ordinary least squares (OLS) linear regression of body mass against a linear measure of size (the body size indicator, BSI) as an index of body condition. These residual indices are used to study the relationship between condition and reproductive investment, survivorship, habitat use, and other parameters. I identify a series of key assumptions underlying the use of this method, each of which is likely to be violated in some or all studies. These assumptions are: (1) that the functional relationship between mass and BSI is linear; (2) that condition is independent of BSI length; (3) that BSI length accurately indicates structural size; (4) that there is no correlation between the size of BSI relative to other structural components (i.e., shape) and the parameter against which the residuals are analyzed; (5) that BSI length is strictly independent of mass; and (6) that BSI length is not subjected to error. Violations of these assumptions place the results of some studies in question and explain the poor relationship observed between OLS residuals and more direct measures of condition. I use avian morphometric data to illustrate how OLS methods can easily lead to Type I and Type II errors through violations of assumptions (5) and (6). Significant relationships reported between OLS residual indices and parameters correlating with body size (e.g., size of sexual ornaments or egg size), are at particular risk of being spurious when the correlation coefficient between mass and BSI is low. Residual indices of condition are often likely to be more reliable when calculated with alternative methods such as nonparametric or model II regression. However, whatever the method used to produce them, residual indices are not suitable for studying the heritability of condition.
Florida's commercial and recre-ational shark landings represent a significant portion of the total U.S. Atlantic shark landings (NMFS, 1993). Shark landings have in-creased significantly during the past decade because human con-sumption of shark meat has become increasingly acceptable and be-cause, in Asian markets, the de-mand for shark fins is very high— as are the prices paid for them (NMFS, 1993; Brown, in press). The east-central coast of Florida is an important area for commercial and recreational shark fishing, and a wide array of shark species, includ-ing those examined in this study, are landed in this region (Trent et al., 1997; FDEP 1). Mercury, a toxic metallic ele-ment, has been shown to bioac-cumulate in fish tissue, and there-fore, fish can represent a major di-etary source of mercury to humans (Phillips and Buhler, 1978; Turner et al., 1980; Lyle, 1986). Methyl-mercury is the most toxic form of mercury for humans to consume (Meaburn, 1978; NMFS, 1993) and essentially all mercury found in fish muscle tissue (>95%) is in the monomethyl form (CH 3 Hg)(Grieb et al., 1990; Bloom, 1992). There-fore, the measurement of total mer-cury provides an approximation of. methylmercury and has been rec-ommended as the standard for regulatory monitoring (Bloom, 1992). Elevated mercury concentra-tions in fish have been a growing concern among resource manage-ment agencies. Apex predators, par-ticularly long-lived species such as billfishes (Förstner and Wittman, Hueter et al., 1995, and oth-ers) have been reported to accumu-late relatively high levels of mercury. In May 1991, the Florida Depart-ment of Health and Rehabilitative Services (FHRS) released a health advisory urging limited consump-tion of all shark species from Florida waters. 2 Owing to mercury concentrations in excess of U.S. Food and Drug Administration and State of Florida standards, FHRS recommended "adults should eat shark no more than once a week; children and women of childbear-ing age should eat shark no more than once a month." State of Florida guidelines recommended that fish containing less than 0.5 ppm of to-tal mercury should represent no dietary risk, fish containing 0.5 to 1.5 ppm of total mercury should be consumed in limited amounts, and fish containing greater than 1.5 ppm of total mercury should not be consumed. The 1991 health advi-sory regarding sharks in Florida waters was derived from a limited number of samples taken from re-tail sources and from studies that lacked important information re-garding species, capture location, sex, and size of sharks examined. Increased landings of sharks in Florida for human consumption (Brown, in press; FDEP 1) has prompted the need for more de-tailed information regarding mer-cury levels in Florida shark species. Consequently, we report here analyses of total mercury levels in the muscle tissue of three carcha-rhinids (bull shark, Carcharhinus leucas; blacktip shark, C. limbatus; and Atlantic sharpnose shark, Rhizo-prionodon terraenovae) and one sphyrnid (bonnethead shark, Sphyr-na tiburo) from the east-central coast of Florida.
Threshold concentrations associated with adverse effects of dietary exposure to methylmercury (MeHg) were derived from published results of laboratory studies on a variety of fish species. Adverse effects related to mortality were uncommon, whereas adverse effects related to growth occurred only at dietary MeHg concentrations exceeding 2.5 µg g(-1) wet weight. Adverse effects on behavior of fish had a wide range of effective dietary concentrations, but generally occurred above 0.5 µg g(-1) wet weight. In contrast, effects on reproduction and other subclinical endpoints occurred at dietary concentrations that were much lower (<0.2 µg g(-1) wet wt). Field studies generally lack information on dietary MeHg exposure, yet available data indicate that comparable adverse effects have been observed in wild fish in environments corresponding to high and low MeHg contamination of food webs and are in agreement with the threshold concentrations derived here from laboratory studies. These thresholds indicate that while differences in species sensitivity to MeHg exposure appear considerable, chronic dietary exposure to low concentrations of MeHg may have significant adverse effects on wild fish populations but remain little studied compared to concentrations in mammals or birds.
Mercury is a toxic heavy metal which is widely dispersed in nature. Most human exposure results from fish consumption or dental amalgam. Mercury occurs in several chemical forms, with complex pharmacokinetics. Mercury is capable of inducing a wide range of clinical presentations. Diagnosis of mercury toxicity can be challenging but can be obtained with reasonable reliability. Effective therapies for clinical toxicity have been described.
Tissue levels of mercury (Hg; total, organic) and selenium (Se) were assessed in juvenile lemon sharks (Negaprion brevirostris) from Florida nearshore waters collected during a harmful algal bloom (HAB, brevetoxin) event and compared with sharks not exposed to HABs. In all sharks studied, total Hg levels in the muscle were generally present in a molar excess over Se (which may protect against Hg toxicity) and mean muscle Hg levels (0.34 microg/g) exceed safe human consumption guidelines. While there was generally no difference in tissue Hg and Se levels following exposure of sharks to HABs, hepatic Hg levels were significantly lower (56% reduction) in the HAB-exposed sharks compared to controls. As Hg and HABs are globally increasing in scope and magnitude, further work is warranted to assess their interactions and biotic impacts within aquatic ecosystems, especially for a species such as the lemon shark that is classified as a near-threatened species by the International Union for the Conservation of Nature.
Sharks are long-lived apex predators which can accumulate toxic metals such as mercury and arsenic. Samples of Sphyrna lewini and Carcharinus porosus were collected from two commercial fish landing sites in Trinidad. Heavy metal concentrations were determined in the muscle, dorsal fin, vertebrae and liver using atomic absorption spectrometric. The provisional tolerable weekly intake (PTWI) and target hazard quotient (THQ) were determined to assess the potential health risks to consumers. Mercury levels ranged between 74–1899 μg/kg in S. lewini and 67–3268 μg/kg in C. porosus. Arsenic levels ranged between 144–2309 μg/kg in S. lewini and 762–6155 μg/kg in C. porosus. Cadmium levels generally ranged between 0.27–27.29 mg/kg in S. lewini and 0.6–29.89 mg/kg in C. porosus. Lead levels generally ranged between 0.14 and 208.81 mg/kg in S. lewini while C. porosus levels ranged between 0.30 and 459.94 mg/kg. The PTWI and THQ values suggest that consumption of these shark species can therefore be a major source of exposure to lead, cadmium, arsenic and mercury in humans and is likely to have potential health risk over long term exposure.
Concentrations of 11 trace elements in three tissues of porbeagle shark Lamna nasus (n = 33) were determined. The maximum observed concentrations of Cd and Pb in muscle were 0.04 and 0.01 mg kg −1 , respectively, and all muscle samples were below European seafood limits for these metals. Hg concentrations in either the red or white muscle that exceeded European regulations for seafood were observed in one-third of specimens. Hg concentration, however, increased with length, and all fish N195 cm had concentrations N1.0 mg kg −1 , with a maximum observed value of 2.0 mg kg −1. Concentrations of Fe and Cu were, on average, 9.7 and 10 times higher in red muscle than in nearby white muscle, respectively. Mn, Zn, As and Se were also found in significantly higher concentrations in red muscle than in white muscle. Crown
The inorganic arsenic species arsenate and arsenite are common environmental toxins which contaminate the drinking water in many countries. Chronic intoxication with arsenicals has been connected with various diseases, but causes also neurological complications and impairs cognitive development, learning and memory. In brain, astrocytes have a pivotal role as partners of neurons in homeostatic and metabolic processes. In addition, astrocytes are the first parenchymal brain cell type which encounters substances which cross the blood-brain barrier and are considered as first line of defence against the toxic potential of xenobiotics. Therefore, astrocytes are likely to play a prominent role in the metabolism and potential detoxification of arsenicals in brain. This article summarizes the current knowledge on the uptake and toxicity of arsenate and arsenite in astrocytes and discusses the modulation of the astrocytic glucose and glutathione metabolism by arsenicals.
The current testing paradigm used in ecotoxicological hazard and risk assessment is well appropriate for chemicals with non-specific modes of action, the question, however is, whether it is appropriate for specifically acting compounds as well. A specific mode of action that is shown by numerous environmental chemicals is immunotoxicity. Immunity is an ecologically relevant trait, which is of key importance for organism survival and population growth against the pressure of pathogens in their environment. However, the environment also imprints genotypic and phenotypic properties of the immune system. Immunologically relevant environmental factors include pathogens as well as toxic chemicals. A complicating factor in detecting immunotoxic effects is the fact that they may be not evident in the resting immune system, but only after immune activation by pathogen challenge. Consequently, risk assessment of chemical-induced disruption of immune function must focus not alone on the relationship between chemical exposure and the response of selected immune parameters, but it has to consider the complex functional properties of this system in its ecological context.
A simple metric (span condition analysis; SCA) is presented for quantifying the condition of sharks based on four measurements of body girth relative to body length. Data on 104 live sharks from four species that vary in body form, behaviour and habitat use (Carcharhinus leucas, Carcharhinus limbatus, Ginglymostoma cirratum and Galeocerdo cuvier) are given. Condition shows similar levels of variability among individuals within each species. Carcharhinus leucas showed a positive relationship between condition and body size, whereas the other three species showed no relationship. There was little evidence for strong differences in condition between males and females, although more male sharks are needed for some species (e.g. G. cuvier) to verify this finding. SCA is potentially viable for other large marine or terrestrial animals that are captured live and then released.
The Greenland shark Somniosus microcephalus is an opportunistic feeder, a top predator, and a very long-lived species. The brain, liver, red and white muscle, gonads, fat, skin, pancreas, and spleen of Greenland sharks from NE Greenland fjords were analysed for PCBs, PCDDs/DFs, PBDEs; DDT isomers; HCH isomers; dieldrin; endrin; HCB; Cd, Hg, Pb, and Se.
PCBs (2.01–103 ng/g wet wt) and PBDEs (7.9–3050 pg/g wet wt) were detected in most of the samples. PCDDs/DFs showed high values when detected. DDTs, HCB and HCHs were only detected in some tissues. The ΣTEQ was 5.76 pg/g in muscle.
Cadmium mainly accumulated in the pancreas and liver (19.6 and 10.7 mg/kg dry wt, respectively); mercury in red muscle (4.10–6.91 mg/kg dry wt); selenium in the pancreas (3.57 mg/kg dry wt) and spleen (1.95 mg/kg dry wt); lead in the skin (0.358 mg/kg dry wt). The selenium-mercury ratio in the liver was also evaluated.
As large long-lived predators, sharks are particularly vulnerable to exposure to methylmercury biomagnified through the marine food web. Accordingly, nonlethal means were used to collect tissues for determining mercury (Hg) concentrations and stable isotopes of carbon (δ(13)C) and nitrogen (δ(15)N) from a total of 69 sharks, comprising 7 species, caught off Southwest Florida from May 2010 through June 2013. Species included blacknose (Carcharhinus acronotus), blacktip (C. limbatus), bull (C. leucas), great hammerhead (Sphyrna mokarran), lemon (Negaprion brevirostris), sharpnose (Rhizoprionodon terraenovae), and tiger sharks (Galeocerdo cuvier). The sharks contained Hg concentrations in their muscle tissues ranging from 0.19 mg/kg (wet-weight basis) in a tiger shark to 4.52 mg/kg in a blacktip shark. Individual differences in total length and δ(13)C explained much of the intraspecific variation in Hg concentrations in blacknose, blacktip, and sharpnose sharks, but similar patterns were not evident for Hg and δ(15)N. Interspecific differences in Hg concentration were evident with greater concentrations in slower-growing, mature blacktip sharks and lower concentrations in faster-growing, young tiger sharks than other species. These results are consistent with previous studies reporting age-dependent growth rate can be an important determinant of intraspecific and interspecific patterns in Hg accumulation. The Hg concentrations observed in these sharks, in particular the blacktip shark, also suggested that Hg may pose a threat to shark health and fitness.
© 2008 The Authors. Journal compilation © 2008 British Ecological Society ... The use of leukocyte profiles to measure stress ... AK Davis1*, DL Maney2 and JC Maerz1 ... 1D.B. Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA 30602, USA; ...
Chronic exposure to arsenic from groundwater has been recognized to cause the largest environmental health disaster in the world, putting more than 100 million people at risk of cancer and other arsenic-related diseases. Depletion of ATP by arsenate has been observed in cellular systems. However, the replacement of phosphate in DNA by arsenic is not firmly established. The toxicity of trivalent arsenicals likely occurs through the interaction of trivalent arsenic species with sulfhydryl groups in proteins. Arsenic binding to a specific protein could alter the conformation and function of the protein as well as its recruitment of and interaction with other functional proteins. Therefore, there has been much emphasis on studies of arsenic binding to proteins, for the purpose of understanding arsenic toxicity and developing arsenic-based therapeutics.
Mining for gold and silver in the El Triunfo mining area, Baja California, Mexico, has
produced > 800,000 tonnes of mine-waste material. The mine has only been active intermittently
since 1748 therefore tailings are scattered in the coastal system. Elemental migration
is mainly caused by winds and tropical hurricanes, thus transported to the beach were metal
deposits are formed. Sediments are discharged into the Pacific Ocean during intense storms
when a sand barrier breaks. To evaluate the geochemistry of the alteration zone and the
migration of the elements along the arroyo, 26 samples of surficial sediment were collected
from close to the gold mine and along the path to the discharge in an evaporitic basin connected
to the Pacific Ocean. Arsenic, Pb and Zn were analyzed with INAA, ICP-OES and ICP-MS
and methods validated using certified reference materials. Elements enriched in the system
shows maximum contents in tailings and ashes of As (50.5%), Pb (9.27 %) and Zn (4.96%)
Sand sediments from the arroyo have maximum contents of arsenic (412 mg kg-1), Pb (1230
mg kg-1) and Zn (1950 mg kg-1). Comparison with background levels and Upper Continental
Crust averages indicate severe contamination of these elements in this coastal system.
Trace element concentrations and oxidative stress indicators were measured in liver and kidney samples of 35 blue sharks caught by local artisan fisheries on the west coast of Baja California Sur (Mexico). Differences between sex and maturity cohorts, and the interactions of trace elements with oxidative stress indicators were assessed. Significant differences were found in trace element (Hg, As, Zn, Cd, Pb) concentration and oxidative stress indicators (catalase (CAT) activity, superoxide dismutase (SOD) activity, lipid peroxidation, TBARS, levels) between tissues. Significant sex differences (females<males) in the hepatic Zn concentration, and maturity (immature<mature) differences in hepatic GPx activity and renal CAT activity were found. Correlations between oxidative stress indicators and trace element concentrations were found: hepatic GST activity - As concentration, SOD activity - protein carbonyl levels, SOD activity - superoxide radical production and Zn concentration - Cd concentration; renal SOD activity - TBARS levels, protein carbonyl levels - As concentration and protein carbonyl levels - Cu concentration. Trace element concentrations may be important drivers of oxidant and antioxidant processes in sharks and an important consideration in their physiology and health.
As a result of mining, forestry, waste disposal and fuel combustion, our environment is becoming increasingly contaminated with heavy metals. The aquatic environment receives waste products from such activities and may be the final depository for these anthropogenically remobilized heavy metals. In order to understand the impact of heavy metals on aquatic biota it is important to characterize the mechanisms available for aquatic life to transport, immobilize and excrete heavy metals.
We analyzed mercury (Hg) concentrations in muscle and liver samples of star-spotted dogfish (Mustelus manazo) caught off the northern region of Japan and compared them with those of spiny dogfish (Squalus acanthias) caught in the same region. The average body length of male star-spotted dogfish specimens was significantly smaller than that of female specimens, reflecting the slower growth rate of male fish. Hg concentrations in liver and muscle increased with increases in body length and estimated age of both male and female star-spotted dogfish specimens. However, the relationships between Hg concentration in liver or muscle and body length or estimated age of male specimens differed markedly from those of female specimens, reflecting differences in growth rate and cessation of growth on reaching maturity. Marked increases in Hg concentration in liver of male and female star-spotted dogfish specimens were observed slightly later than increases in Hg concentration in muscle of those specimens due to growth cessation. These marked increases in Hg in liver may reflect increases in Hg due to the formation of mercury selenide. Similar results were previously reported in spiny dogfish specimens, except spiny dogfish showed only trace levels of Hg in liver (Endo et al., Chemosphere 77:1333-1337, 2009). The greater lipid content in liver and the larger liver size in spiny dogfish may explain the much lower levels of Hg observed in liver of spiny dogfish compared with those in the star-spotted dogfish.
A number of contaminants affect fish health, including mercury and selenium, and the selenium:mercury molar ratio. Recently the protective effects of selenium on methylmercury toxicity have been publicized, particularly for consumption of saltwater fish. Yet the relative ameliorating effects of selenium on toxicity within fish have not been examined, nor has the molar ratio in different tissues, (i.e. brain). We examined mercury and selenium levels in brain, kidney, liver, red and white muscle, and skin and scales in bluefish (Pomatomus saltatrix) (n=40) from New Jersey to determine whether there were toxic levels of either metal, and we computed the selenium:mercury molar ratios by tissues. Total mercury averaged 0.32±0.02ppm wet weight in edible muscle and 0.09±0.01ppm in brain. Selenium concentration averaged 0.37±0.03 in muscle and 0.36±0.03ppm in brain. There were significant differences in levels of mercury, selenium, and selenium:mercury molar ratios, among tissues. Mercury and selenium levels were correlated in kidney and skin/scales. Mercury levels were highest in kidney, intermediate in muscle and liver, and lowest in brain and skin/scales; selenium levels were also highest in kidney, intermediate in liver, and were an order of magnitude lower in the white muscle and brain. Mercury levels in muscle, kidney and skin/scales were positively correlated with fish size (length). Selenium levels in muscle, kidney and liver were positively correlated with fish length, but in brain; selenium levels were negatively correlated with fish length. The selenium:mercury molar ratio was negatively correlated with fish length for white muscle, liver, kidney, and brain, particularly for fish over 50cm in length, suggesting that older fish experience less protective advantages of selenium against mercury toxicity than smaller fish, and that consumers of bluefish similarly receive less advantage from eating larger fish.
Ecological risk assessments (ERAs) are employed to quantify and predict the vulnerability of a particular species, stock or population to a specific stressor, e.g. pollution, harvesting, climate change, by-catch. Data generated from ERAs are used to identify and prioritize species for implementation of effective conservation and management strategies. At this time, ERAs are of particular importance to elasmobranchs, given the ecological importance and documented global population declines of some elasmobranch species. Here, ERAs as a tool for elasmobranch conservation and management are reviewed and a theoretical roadmap provided for future studies. To achieve these goals, a brief history of ERAs and approaches used within them (in the context of elasmobranchs) are given, and a comprehensive review conducted of all ERA studies associated with elasmobranchs published between 1998 and 2011. The hazards assessed, species evaluated and methodological approaches taken are recorded. Chronological and geographical patterns suggest that this tool has grown in popularity as a commercial fishery management instrument, while also signalling a recent precautionary approach to elasmobranch management in commercial fisheries globally. The analysis demonstrates that the predominant parameters incorporated in previous ERAs are largely based on life-history characteristics, and sharks have received the majority of attention; batoids (including skates) have received less attention. Recreational fishing and habitat degradation are discussed as hazards which warrant future investigation through ERA. Lastly, suggestions are made for incorporating descriptive ecological data to aid in the continued development and evolution of this management tool as it applies to future elasmobranch conservation.
The exact relationship between disease incidence in aquatic organisms and environmental pollution is not well defined. A number of mechanisms by which aquatic pollutants may act to increase disease incidence in fish have been speculated, many suggesting immunosuppression as a link in the etiology of disease among fishes in highly contaminated areas. This article will review the effects of metal pollutants on the immune responses of fish by examining in vitro and in vivo laboratory studies carried out since 1980. It will also describe how those alterations may be responsible for pollution-associated diseases in directly exposed fish. While a large number of environmental contaminants represent aquatic pollutants of concern (e.g. polycyclic aromatic hydrocarbons, chlorinated organics, and pesticides), heavy metals were selected as the pollutants for this review because of their: (a) prevalence in polluted aquatic environments; (b) immunotoxic potential in mammalian systems; (c) ability to induce tumors in exposed rodents; and (d) their overall toxicity in a variety of species. It can be concluded that a number of heavy metal pollutants shown to be immunotoxic in mammalian systems, including cadmium, chromium, copper, lead, manganese, nickel, and zic, also alter immunoregulatory functions in a variety of fish species. These alterations may ultimately lead to increased host susceptibility to infectious and malignant diseases in fish inhabiting heavy metal-contaminated waters.
The transition metals zinc, iron and copper are common constituents in a wide range of proteins. Although these metals are all essential for life, when present in excess, they are frequently toxic to cell growth and viability. Therefore, all organisms rely on sophisticated mechanisms to maintain optimal levels of each metal. Genes that encode metal transport or storage proteins are often regulated at the transcriptional level in response to changes in metal status. In this review, we focus on what is known about the transcription factors that mediate these metal-dependent changes. Specifically, we highlight recent advances in our understanding of the mechanisms by which these factors sense metal ions.
We analyzed Hg, Zn and Cu concentrations in the liver and muscle of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan. The Hg concentration in the muscle increased proportionally with body length in the tiger sharks, whereas that in the liver increased rapidly after maturity (defined by a length of over 2.7 m). Muscle Hg levels were higher than liver concentrations in immature sharks, with the inverse trend observed in mature sharks. Notably, the Zn and Cu concentrations in the liver tended to decrease with increasing body length. This rapid increase in hepatic Hg concentration concurrent with the onset of maturity in sharks may result from the continuous intake of Hg via food and the slower growth of mature sharks. The high concentrations of the essential metals Zn and Cu in immature sharks may be explained by the physiological demands related to rapid growth.
Due to the extremely high affinity of selenium (Se) to mercury (Hg), Se sequesters Hg and reduces its biological availability in organisms. However the converse is also true. Hg sequesters Se, causing Hg to inhibit the formation of Se dependent enzymes while supplemental Se supports their continued synthesis. Hence, whether or not toxic effects accompany exposure to Hg depends upon the tissue Se:Hg molar ratio of the organism. The main objective of the present study was to investigate how levels of Hg and Se affected metallothionein (MT) induction in free-ranging brown trout, Salmo trutta, from Lake Mjøsa, Norway (a Se depauperate lake). MT is proposed as a sensitive biomarker of potential detrimental effects induced by metals such as Hg. Emphasis was addressed to elucidate if increased tissue Se:Hg molar ratios and Se levels affected the demands for MT in the trout. The Se:Hg molar ratio followed by tissue Se levels were most successful for assessing the relationship between metal exposure and MT levels in the trout. Thus, Hg in molar excess over Se was a stronger inducer of MT synthesis than tissue Hg levels in the trout, supporting the assumption that Se has a prominent protective effect against Hg toxicity. Measuring Hg in animals may therefore provide an inadequate reflection of the potential health risks to humans and wildlife if the protective effects of Se are not considered.
Distributions of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the northern Bohai and Yellow Seas, China, were investigated. An ecological risk assessment of arsenic and metals in the sediments was evaluated by three approaches: the Sediment Quality Guidelines (SQGs) of the United States Environmental Protection Agency (USEPA), the degree of contamination, and two sets of SQGs indices. Sediments from the estuaries of the Wuli and Yalu Rivers contained some of the greatest concentrations of arsenic, cadmium, copper, mercury, lead, and zinc. Median concentrations of cadmium and mean concentrations of lead and zinc were greater than background concentrations determined for the areas. All sediments were considered to be heavily polluted by arsenic, but moderately polluted by chromium, lead, and cadmium. Current concentrations of arsenic and metals are unlikely to be acutely toxic, but chronic exposures would be expected to cause adverse effects on benthic invertebrates at 31.4% of the sites.
The impact of acute and sublethal toxicity of arsenate on hematological, biochemical and enzymological parameters of an Indian major carp Catla catla were estimated. The median lethal concentration of sodium arsenate to the fish Catla catla for 96h was found to be 43.78 mg/L. During acute treatment (43.78 mg/L), hemoglobin (Hb), hematocrit (Ht), red blood cell count (RBC), white blood cell count (WBC), plasma glucose, plasma protein, liver aspartate and alanine aminotransferase (AST and ALT) levels decreased, whereas corpuscular indices like mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) increased in arsenate treated fish. In sublethal treatment (4.378 mg/L), Hb, Ht, RBC, plasma protein levels decreased while MCHC and plasma glucose levels increased throughout the exposure period. A biphasic trend was noticed in WBC, MCV, MCH, liver AST and ALT levels. The alterations of these parameters can be effectively used as a rapid method to assess health of fish exposed to arsenate in the aquatic environment.
Total mercury (THg) and monomethylmercury (MMHg) concentrations were determined in the tissues of demersal shark (Order Squaliformes and the Families: Scyliorhinidae, Hexanchidae) and chimaera species (Families: Chimaeridae and Rhinochimaeridae) from continental shelf and slope waters off southeast Australia, including embryos, juveniles and adults. The distribution of THg in various tissues (muscle, liver, kidney and skin), examined in ten species, shows higher levels in the muscle tissue (1.49+/-0.47mgkg(-1), ww), which accounted for between 59% and 82% of the total body burden of mercury and in the kidney (0.93+/-0.14mgkg(-1), ww) and liver (0.61+/-0.25mgkg(-1), ww) with lower levels observed in the skin (0.12+/-0.06mgkg(-1), ww). Additional THg determinations were performed in the muscle tissue of five other species allowing geographical and inter-specific comparisons. Speciation analysis demonstrated that more than 90% mercury was bound in muscle tissue as MMHg with higher percentages (>95%) observed in sharks species occupying deeper environments. Species differences were observed. Highest THg levels in the muscle tissue (up to 6.64mgkg(-1) wet weight, ww) were recorded in Proscymnodon plunketi and Centrophorus zeehaani (mean values; 4.47+/-1.20 and 3.52+/-0.07mgkg(-1), ww, respectively). Consistent with the ongoing paradigm on mercury bioaccumulation, we systematically observed THg concentrations increasing with animal size from the embryos to the larger sharks. Embryos of Etmopterus baxteri and Centroselachus crepidater had average levels 0.28 and 0.06mgkg(-1) (ww), while adult specimens reached 3.3 and 2.3mgkg(-1) (ww), respectively. THg concentrations in Australian sharks were compared with the same genus collected in other world regions. Levels were closer to data reported for East Atlantic than for the epicontinental Mediterranean margins. At a smaller geographical scale, the habitat effect on mercury concentration in sharks seems less clear. Squalid sharks occupying shelf waters showed higher mean mercury levels relative to their size (body weight, bw) than mid-slope species (0.4-6.7mgkg(-1) bw and 0.3-2.2mgkg(-1) bw, respectively). However, local regional differences (East and South Tasmania vs. Victoria) in Hg levels were not detected for the majority of taxa examined. All species, with the exception of Figaro boardmani showed values greater than 0.5mgkg(-1) (ww) and all but four were above many international regulatory thresholds (1.0mgkg(-1), ww).