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Bioaccumulation and biomagnification of mercury and methylmercury in four sympatric coastal sharks in a protected subtropical lagoon
... Anthropogenic contributions of Hg have increased surface ocean Hg concentrations since the 19th-century Industrial Revolution (Doney, 2010;Driscoll et al., 2013). Once Hg enters the marine environment, it is biomagnified, with high trophic level organisms at a great risk of accumulating potentially elevated concentrations (Matulik et al., 2017). Marine predators, particularly long-lived shark species, are known to contain high levels of Hg (Tiktak et al., 2020). ...
... For both PTH and BTH, muscle THg concentrations in this study were similar to the same species documented for the Galápagos Marine Reserve, southwestern Indian Ocean, Baja California Sur and Colombian Pacific coast (Kiszka et al., 2015;Le Bourg et al., 2019;Lara et al., 2020;Maurice et al., 2021). The percentage of Hg burden presented as MeHg exceed 90 % in several studies regarding the muscle tissue (Matulik et al., 2017;Pethybridge et al., 2010), supporting the results that the Hg determined in both thresher shark species was apparently MeHg as their estimated mean was indistinguishable from 100 %. For PTH livers, the THg concentrations were lower than the previous studies sampled from Mexico Pacific coast (0.37 ± 0.31 μg g −1 ww) (Lara et al., 2020). ...
... Though juvenile and adult BTH demonstrated dietary shifts, their tropic positions changed little with body size indicating that these pelagic sharks adopt a generalist strategy over their life history. A lack of correlation has been reported by multiple studies (Newman et al., 2011;Endo et al., 2015Endo et al., , 2016Matulik et al., 2017;Gelsleichter et al., 2020), reinforcing the hypothesis that trophic positions have limited effects on Hg accumulation in thresher sharks. ...
Sharks, as top order predators, provide a guidance on how contaminants such as mercury bioaccumulate in marine environments. This study assessed the bioaccumulation of mercury (total mercury, THg) in the muscle, liver, red blood cells (RBC), and plasma of pelagic and bigeye thresher sharks (Alopias pelagicus and A. superciliosus) from eastern tropical Pacific. Additionally, the concentration of methylmercury (MeHg) in muscle was also determined to assess risks for human consumption. For both species, muscle THg concentrations (4.05 ± 2.15 and 4.12 ± 1.84 μg g-1 dry weight for pelagic and bigeye thresher shark) were higher than that in other tissues. THg concentrations for all tissues were significantly correlated with precaudal length, with higher accumulation rates after maturity in pelagic than bigeye thresher sharks, suggesting an associated dietary shift at maturation. Correlations among tissues in both species suggested similar transportation and distribution patterns in internal tissues. The δ13C values in muscle, RBC and plasma suggested that habitat shifts influenced Hg accumulation, whereas trophic position, estimated by δ15N values, had limited effects on patterns of Hg bioaccumulation. Diet shifts towards prey more cephalopods that content higher Hg than small fishes (large fishes: 1.77 μg g-1; cephalopods: 0.66 μg g-1 and small fishes 0.48 μg g-1, dry weight) increased Hg accumulation rates in adult pelagic thresher sharks. Concentrations of MeHg in the muscle of both thresher shark (3.42 ± 1.68 μg g-1 in A. pelagicus and 3.78 ± 2.13 μg g-1 in A. superciliosus) exceeded the recommended levels for human consumption. This research provides insight into the factors influencing mercury bioaccumulation in thresher sharks, which are essential for the management and conservation of these species.
... particularly concentrated in sharks(O'Bryhim et al., 2017).Due to its low excretion rate in marine fauna, Hg bioaccumulates in organisms with size and age (Figure 2-8), a pattern globally observed in sharks(Biton-Porsmoguer et al., 2018;Chouvelon et al., 2018;Le Bourg et al., 2019;Matulik et al., 2017;McKinney et al., 2016). In the meantime, due to both efficient trophic transfer of MeHg in aquatic food webs and weak Hg elimination rate in marine biota, long-lived apex predators tend to accumulate higher Hg concentrations in their tissues than baseline organisms, a mechanism referred to as biomagnification(Figure 2-8). ...
... In the meantime, due to both efficient trophic transfer of MeHg in aquatic food webs and weak Hg elimination rate in marine biota, long-lived apex predators tend to accumulate higher Hg concentrations in their tissues than baseline organisms, a mechanism referred to as biomagnification(Figure 2-8). Biomagnification of Hg is commonly observed in nearly all aquatic food-webs(Lavoie et al., 2013) with trophic position representing the principal factor of MeHg or total Hg concentrations in higher consumers(Biton-Porsmoguer et al., 2018;Le Bourg et al., 2019;Matulik et al., 2017;McKinney et al., 2016;Senn et al., 2010). As long-lived predators at the top of food webs, sharks naturally exhibit high mercury concentrations (LeBourg et al., 2019;Schartup et al., 2019). ...
... Measurements were carried out using a Direct Mercury Analyzer (DMA-80, Milestone, USA) (Observatoire Midi-Pyrénées, Toulouse, France). Measured total Hg concentration was used as a proxy for MeHg as it is the dominant form in shark muscle (e.g.,Matulik et al., 2017) especially for the species of interests analyzed in this work (i.e., smooth hammerhead, blue and shortfin mako sharks)(Carvalho et al., 2014;Kim et al., 2016;Storelli et al., 2003). According to Hg concentration in each sample, successive acid digestions were performed on another dry muscle sample to convertsolubilized MeHg to inorganic Hg and reach a Hg concentration of 1 ng·mL -1 in the final mixture analyzed by MC-ICP-MS. ...
Characterizing the trophic ecology of sharks is fundamental to understand the potential cascading effects of their current décline in marine ecosystems. This thesis investigates the trophic niches of shark species in Coastal and offshore ecosystems around Baja California Sur (Mexico) in both the Pacific Ocean and the Gulf of California, a region characterized by a strong pressure from artisanal fisheries. Ecologically, the guiding thread was to elucidate the importance of resource partitioning in shaping shark realized trophic niches, at both the intra- and inter-specific level. To achieve this objective, multiple trophic biomarkers were used, such as carbon, nitrogen and mercury stable isotopes, and fatty acid compositions, to describe the vertical and horizontal dimensions of shark foraging habits.At the intra-specific level, resource partitioning was supported by the use of distinct ecosystems for juvenile hammerhead sharks due to ontogenetic shifts in habitat and prey. Inter-specific resource partitioning seems to be driven by foraging at different depth within pelagic assemblages, but could also depend on local environmental conditions, such as upwelling activity. This work also characterized the life cycle of a poorly studied hammerhead species, the smooth hammerhead shark (Sphyrna zygaena). The prolonged Coastal residency of this species through ontogeny suggests significant vulnerability to local artisanal fisheries. Finallly, the demonstrated complementarity of trophic markers provides a promising insight to unravel food web structure and ecological mechanisms.
... Mercury (Hg) poisoning has been implicated in central nervous system and brain damage, infant death, and can retard fetal cognitive development when mothers consume mercury-containing seafood [15,16]. The burning of fossil fuels is the primary source of atmospheric mercury [17], which then dissolves in the oceans, where Hg concentrations in surface waters have increased by a factor of three since the industrial revolution [18][19][20]. In marine systems, bacteria transform mercury into its organic form, methylmercury (MeHg), where it has the potential to accumulate and biomagnify in large upper trophic level predators, such as sharks [20][21][22][23]. ...
... The burning of fossil fuels is the primary source of atmospheric mercury [17], which then dissolves in the oceans, where Hg concentrations in surface waters have increased by a factor of three since the industrial revolution [18][19][20]. In marine systems, bacteria transform mercury into its organic form, methylmercury (MeHg), where it has the potential to accumulate and biomagnify in large upper trophic level predators, such as sharks [20][21][22][23]. Unsurprisingly, shark fins consumed in soups frequently exceed safe mercury concentrations, with some studies showing all examined samples significantly above the established maximum limits for mercury consumption [22]. ...
... Studies show that children and adults who consume shark products once a week are exposed to three times more mercury than what is recommended by the United States Environmental Protection Agency (U.S. EPA) [24]. While the majority of studies generally report mercury and levels of other toxic elements in muscle tissue, the liver or from vertebrae where they readily accumulate [20,24,25], it is important to note that fins can contain higher levels of mercury and other toxic elements, such as lead and cadmium, in comparison to muscle and other non-fin tissues [23,26]. Additionally, work performed in Hong Kong and China shows that the total amount of mercury found in shark fins regularly exceeded the prescribed Hong Kong and China legal limit of 0.5 ppm [22], and the 1 ppm legal limit used for predatory fish in Singapore [27]. ...
Shark fin soup, consumed by Asian communities throughout the world, is one of the principal drivers of the demand of shark fins. This near USD 1 billion global industry has contributed to a shark population declines of up to 70%. In an effort to arrest these declines, the trade in several species of sharks is regulated under the auspices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Despite this legal framework, the dried fins of trade-regulated sharks are frequently sold in markets and consumed in shark fin soup. Shark fins found in soups break down into a fibrous mass of ceratotrichia, meaning that identifying the species of sharks in the soup becomes impossible by visual methods. In this paper, we use DNA barcoding to identify the species of sharks found in bowls of shark fin soup collected in Singapore. The most common species identified in our samples was the blue shark (Prionace glauca), a species listed as Near Threatened on the International Union for Conservation of Nature (IUCN) Red List with a decreasing population, on which scientific data suggests catch limits should be imposed. We identified four other shark species that are listed on CITES Appendix II, and in total ten species that are assessed as Critically Endangered, Endangered or Vulnerable under the IUCN Red List of Threatened Species. Globally, the blue shark has been shown to contain levels of mercury that frequently exceed safe dose limits. Given the prevalence of this species in the examined soups and the global nature of the fin trade, it is extremely likely that consumers of shark fin soup will be exposed to unsafe levels of this neurotoxin.
... Top predators in terrestrial and aquatic systems, including estuarine and marine systems, have been found to have elevated MeHg levels in their tissues (Wiener et al. 2003). Recent surveys of sharks from south Florida coastal waters, both on the southwest coast and Florida Bay (Matulik et al. 2017) found these top predators had higher Hg concentrations than previously reported for conspecifics from Florida (Adams and McMichael 1999;Adams et al. 2003;Hueter et al. 1995). Consequently, the Florida Department of Health (FDOH) advises that young children and women of childbearing age should not consume any shark and others should limit consumption of small sharks (<43 inches or approximately 109 centimeters) to one meal a month while avoiding larger sharks (Florida Department of Health 2018). ...
... Because the vast majority of THg has been found to be in the form of MeHg in muscle tissues of bony fish (Hall et al. 1997) and many sharks (Storelli et al. 2003, Pethybridge et al. 2010, Nam et al. 2011, Matulik et al. 2017, the present study like many others considered them equivalent. This use of THg as a proxy for MeHg in tissues such as liver and kidney, while also done by others (Bergés-Tiznado et al. 2015;O'Bryhim et al. 2017), should, however, be viewed cautiously. ...
... Some studies report concentrations decreasing with increasing size due to growth dilution when dietary exposure is low (Lyons et al. 2013a;Ward et al. 2010). Other studies report that elevated concentrations in young organisms whose dietary exposure is high offsets any effect of growth dilution (Adams and McMichael 1999;Matulik et al. 2017). In the present study, there were no statistically significant correlations between muscle [THg] and size for neonates. ...
Elasmobranchs are exposed to mercury (Hg) through a variety of pathways in the environment. This study assessed maternal offloading and diet-based Hg exposure for neonatal and juvenile blacktip sharks (Carcharhinus limbatus) from Charlotte Harbor located along southwest Florida’s coast, a recognized Hg hotspot. Neonates (n = 57) had highest total Hg (THg) concentrations in the kidney (0.56 ± 0.26 mg kg−1; n = 38) and muscle (0.53 ± 0.17 mg kg−1; n = 57), followed by liver (0.31 ± 0.11 mg kg−1; n = 38), and blood (0.05 ± 0.033 mg kg−1; n = 57). Juveniles (n = 13) exhibited a different distribution with highest THg in the liver (0.868 ± 0.54 mg kg−1; n = 6), followed by the muscle (0.84 ± 0.28 mg kg−1; n = 13), kidney (0.55 ± 0.22 mg kg−1; n = 6), and blood (0.11 ± 0.04 mg kg−1; n = 11). The distribution of THg among tissues and liver-to-muscle ratios indicated that Hg originated primarily from maternal offloading in neonates, whereas juveniles continued to accumulate Hg through dietary exposure post-parturition. Additionally, comparisons between results of the present study and previous Florida blacktip shark surveys suggested that Hg levels have not declined in southwest Florida estuaries for over two decades.
... By measuring element concentrations in aquatic consumers and comparing these with national and international standards, risks to human health can be assessed (insert relevant ref). Concurrently, chemical tracers, such as the analysis of nitrogen stable isotopes (d 15 N), provide a well-established technique to understand the flow of trace elements through food webs (Matulik et al., 2017). Through known fractionation at each trophic level, d 15 N values of consumers represent the assimilation of prey resources across trophic levels (Fry, 2005) providing insight into diet and trophic relationships (Hussey et al., 2012(Hussey et al., , 2015 and allowing investigation of element biomagnification/biodilution dynamics (Endo et al., 2015;Huang, 2016). ...
... In contrast to As, there was a positive relationship between Hg and d 15 N values across species. This relationship identifies biomagnification whereby species feeding at a higher trophic level had higher levels of Hg (Matulik et al., 2017). Similarly to our results, biomagnification of Hg has also been reported at the species level for Carcharhinus leucas and Carcharhinus acronotus from Florida Bay (Matulik et al., 2017), and Carcharhinus leucas and Sphyrna lewini from the southwestern Indian Ocean (Le Bourg et al., 2014). ...
... This relationship identifies biomagnification whereby species feeding at a higher trophic level had higher levels of Hg (Matulik et al., 2017). Similarly to our results, biomagnification of Hg has also been reported at the species level for Carcharhinus leucas and Carcharhinus acronotus from Florida Bay (Matulik et al., 2017), and Carcharhinus leucas and Sphyrna lewini from the southwestern Indian Ocean (Le Bourg et al., 2014). ...
Here, we evaluated the levels of As, Hg, Pb, and Cd in shark meat sold along the Amazon Coast of Brazil and used nitrogen stable isotope values to determine trophic position and to assess element biomagnification. From market samples, a total of 13 species were identified via molecular analysis, including those listed as endangered and vulnerable by the IUCN Red List. Arsenic was present in significantly higher concentrations than all other elements, followed by Hg, with the highest mean concentrations recorded in M. higmani (As: 19.46 ± 8.79 μg/g ww) and C. acronotus (Hg: 1.12 ± 0.68 μg/g ww). Lead and Cd were recorded at much lower levels in all species. The EWI of individual elements were above PTWI for all species when considering Hg, seven species for inor- ganic arsenic (iAs), and one species for Pb. The weekly consumption of 10 species should be reduced to less than 416.39 g, which is equivalent to the daily estimated fish consumption rate in the region. The mean (±SD) δ15N values of species ranged from 10.7 ± 0.51‰ in M. higmani to 14.2 ± 0.59‰ in C. porosus, indicating feeding over >1 trophic level. Arsenic was negatively correlated with δ15N values, while Hg was positively correlated indicating biodilution and biomagnification, respectively. Our results indicate that the sale and consumption of shark meat will expose consumers to potentially harmful levels of iAs and Hg, as well as contributing to the pop- ulation decline of species including those that are currently categorized as threatened.
... As Hg accumulation is affected by trophic activity, it may appear surprising that we found no significant relationship between muscle THg concentrations and δ 15 N in Cat Island oceanic whitetip sharks. However, it is important to note that this observation is common in the literature; in fact, out of the sizeable number of studies that have examined intraspecific relationships between Hg accumulation and δ 15 N-derived trophic position in chondrichthyans, only a third (20 out of 60) of these associations were found to be significantly correlated (Domi et al. 2005, Endo et al. 2009, 2015, Pethybridge et al. 2010, Newman et al. 2011, Rumbold et al. 2014, Teffer et al. 2014, Kiszka et al. 2015, Kim et al. 2016, Matulik et al. 2017, Le Bourg et al. 2019. No studies to date have presented explanations for the conflicting results observed in these studies (other than low sample size; Pethybridge et al. 2010); however, Teffer et al. (2014) suggested that a lack of significant relationships between Hg concentrations and δ 15 N in single species (referring specifically to dolphinfish Cory phaena hippurus, yellowfin tuna Thunnus albacares, and albacore tuna T. alalunga) could result from sampling a narrow size range. ...
... However, whether this is possible remains questionable because many shark species have been shown to accumulate Hg at levels well above the LOAEL without any apparent effects on health or reproduction (e.g. Matulik et al. 2017). Given this, it is likely that sharks exhibit higher thresholds for Hg-associated effects than other fishes, especially considering that the LOAEL is largely based on studies of Hg effects in freshwater teleosts. ...
... As demonstrated by this study and previous research (Rumbold et al. 2014, Matulik et al. 2017, O'Bryhim et al. 2017, muscle biopsies provide an effective, non-lethal approach for assessing Hg exposure and uptake in sharks and their relatives. ...
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.
... Se observa que los ejemplares de tamaño mediano fueron los que más concentración metálica tuvieron para el Al, Cr, Li, Ni y V, los ejemplares más grandes tuvieron mayor concentración metálica en el caso del B, Cd, Fe y Zn; solo el Cu y el Pb tuvieron mayor concentración en los ejemplares más pequeños. Los ejemplares medianos y los grandes son los que acumulan más concentración de metales esto es debido al proceso de bioacumulación en los organismos de mayor peso (Matulik et al., 2017;Turoczy et al., 2000;Wang et al., 2019a). Estas diferencias también influyen en la dieta que tienen los ejemplares pequeños, ya que estos se alimentan de organismos más pequeños del plancton (Castro, 1993;Gushchin y Corten, 2017), debido a esto el metabolismo actúa de distintas formas incluso llegando a tener en algunos metales una mayor acumulación como es en nuestro caso con el Pb y Cu (Norambuena et al., 2015;Wood et al., 2017). ...
... Solo el Li tuvo mayor concentración en los ejemplares de mediano tamaño. Los ejemplares grandes acumulan más concentración de metales debido al proceso de bioacumulación en los organismos de mayor peso (Matulik et al., 2017;Turoczy et al., 2000;Wang et al., 2019a). La dieta que tienen los ejemplares pequeños se alimentan de organismos más pequeños del plancton (Castro, 1993;Gushchin y Corten, 2017), debido a esto el metabolismo actúa de distintas formas incluso llegando a tener en algunos metales una mayor acumulación (Norambuena et al., 2015;Wood et al., 2017). ...
... Los ejemplares más grandes tuvieron mayor concentración en el Cr, Cu, Fe, Pb y V. El Al, B, Cd, Ni y Zn tuvieron mayores concentraciones en los ejemplares más pequeños analizados. Los ejemplares medianos y los grandes son los que acumulan más concentración de metales esto es debido al proceso de bioacumulación en los organismos de mayor peso (Matulik et al., 2017;Turoczy et al., 2000;Wang et al., 2019). Estas diferencias también influyen en la dieta que tienen los ejemplares pequeños, ya que estos se alimentan de organismos más pequeños del plancton (Castro, 1993;Gushchin y Corten, 2017), debido a esto el metabolismo actúa de distintas formas incluso llegando a tener en algunos metales una mayor acumulación como es en nuestro caso con el Pb y Cu (Norambuena et al., 2015;Wood et al., 2017 ...
Los organismos marinos están expuestos a grandes alteraciones producidas por el hombre debido a los vertidos en los océanos, por lo que el estudio de la contaminación y polución marina es de gran valor para cada ecosistema. Para este estudio se han recolectado 963 ejemplares de peces pelágicos, de los cuales 345 son de caballa (Scomber colias), 294 de chicharro (Trachurus picturatus) y 324 de sardina (Sardina pilchardus). El estudio abarcó un total de 2 años, desde junio de 2016 y hasta mayo de 2018.
Se estudiaron 16 muestras de cada especie cada mes, durante los 2 años de muestreo, procedentes de los muestreos realizados por el Centro Oceanográfico de Canarias del Instituto Español de Oceanografía (COC-IEO) en las lonjas de la Isla de Tenerife. Se determinó en cada muestra la concentración de 11 metales de carácter antrópico mediante la técnica de Espectrometría de Emisión Óptica con Plasma Acoplado Inductivamente (ICP-OES).
Se realizaron estudios estadísticos con factores como la estación oceanográfica, el año de recolección, el nivel de madurez de las gónadas, el peso y longitud de los ejemplares y la concentración de clorofila en el océano en el periodo de muestreo. S. colias fue la especie que presentó mayor concentración en un mayor número de metales. S. pilchardus presenta mayor concentración en Cu, Li y Zn, en la estación cálida. Estos son metales de un carácter muy antrópico en costas; esta especie tiende a acercarse más a las costas respecto a las otras dos y es la causa de que presente mayor concentración en estos metales debido a la influencia de la contaminación ligada a la costa. Los ejemplares inmaduros de las tres especies presentaron mayor concentración en más metales que los ejemplares maduros.
Este hecho puede deberse a que estos ejemplares requieren de una tasa metabólica mucho mayor debido a su crecimiento y no detoxifican igual que los ejemplares maduros. Ningún metal pesado tóxico alcanzó el valor máximo de ingesta diaria admisible fijado y las concentraciones de Cd y Pb presentan valores muy por debajo de los límites máximos admitidos (CMA) para su consumo alimentario.
... In recent decades there has been a rapid proliferation of scientific studies describing the relative concentrations of Cd, Hg, and Pb in the tissues of higher marine consumers, especially those that comprise a substantial proportion of the global seafood trade (Fraser et al., 2013). Concentrations are often highest in large bodied, slow-growing species that exhibit high relative trophic positions, such as tunas (Kumar, 2018;Lee et al., 2016), swordfish (Barone et al., 2018), and elasmobranchs (Matulik et al., 2017;Rumbold et al., 2014;Shipley et al., 2021;Tiktak et al., 2020). Elasmobranchs (sharks, skates, and rays) are a speciose and globally distributed group of taxa (Carrier et al., 2012). ...
... Given that the persistent consumption of elasmobranch meat can have detrimental impacts for human consumers, much of the existing literature has focused on describing the relative concentrations of Cd, Hg, and Pb in various elasmobranch species and tissues in relation to recommended exposure thresholds (e.g., Matulik et al., 2017;Merly et al., 2019;Shipley et al., 2021). However, the actual health impacts of high Cd, Hg, and Pb concentrations in elasmobranchs have not yet been well investigated, nor the physiological mechanisms to counteract high tissue concentrations considered highly toxic. ...
... Total Hg (THg) concentration was determined on aliquots (around 10 mg) of homogenized samples by combustion, gold trapping and atomic absorption spectrophotometry using a DMA80 analyzer (Milestone, USA). As THg is predominantly in the MeHg form in shark muscle (Le Croizier et al., 2020b;Matulik et al., 2017;Pethybridge et al., 2010a;de Carvalho et al., 2014;Bosch et al., 2016;Nalluri et al., 2014), THg was used as a proxy for MeHg concentration, in accordance with previous studies (Le Croizier et al., 2020a;Besnard et al., 2021). Total Hg concentrations in samples are expressed on a dry weight basis (µg⋅g − 1 dw). ...
... Moreover, MeHg stored in muscle comes from the residual blood MeHg exiting from the liver after in vivo demethylation. As MeHg is the dominant form of Hg in shark muscle (Le Croizier et al., 2020b;Matulik et al., 2017;de Carvalho et al., 2014), increased Hg concentration in the muscle of Australasian sharks may imply that trophic exposure to MeHg exceeds demethylation capacity. Our findings are consistent with a previous study which observed an increase in Hg concentration with size in juvenile EA individuals (Gilbert et al., 2015). ...
Large marine predators exhibit high concentrations of mercury (Hg) as neurotoxic methylmercury, and the potential impacts of global change on Hg contamination in these species remain highly debated. Current contaminant model predictions do not account for intraspecific variability in Hg exposure and may fail to reflect the diversity of future Hg levels among conspecific populations or individuals, especially for top predators displaying a wide range of ecological traits. Here, we used Hg isotopic compositions to show that Hg exposure sources varied significantly between and within three populations of white sharks (Carcharodon carcharias) with contrasting ecology: the north-eastern Pacific, eastern Australasian, and south-western Australasian populations. Through Δ200Hg signatures in shark tissues, we found that atmospheric Hg deposition pathways to the marine environment differed between coastal and offshore habitats. Discrepancies in δ202Hg and Δ199Hg signatures among white sharks provided evidence for intraspecific exposure to distinct sources of marine methylmercury, attributed to population and ontogenetic shifts in foraging habitat and prey composition. We finally observed a strong divergence in Hg accumulation rates between populations, leading to three times higher Hg concentrations in large Australasian sharks compared to north-eastern Pacific sharks, and likely due to different trophic strategies adopted by adult sharks across populations. This study illustrates the variety of Hg exposure sources and bioaccumulation patterns that can be found within a single species and suggests that intraspecific variability needs to be considered when assessing future trajectories of Hg levels in marine predators.
... Zafeiraki et al., 2019), and the majority of these were limited to single tissue analyses (e.g. Adams and McMichael, 1999;Storelli et al., 2002;Maz-Courrau et al., 2012;Gilbert et al., 2015;Kim et al., 2016;Matulik et al., 2017;Á lvaro-Berlanga et al., 2021;Shipley et al., 2021). As a consequence, multi-species studies that concurrently investigate the presence of multiple pollutants in more than one tissue are still limited, leaving a gap of knowledge on the species-specific accumulation profile, organotropism, and trophic transfer of pollutants. ...
... Considering the general difficulty in comparing species from different areas, trophic magnification factors appear to be a reliable and quantitative tool to assess and better understand the contaminant bioaccumulation (Borgå et al., 2012). Upper trophic level marine fish derive a large proportion of their total body TE loads through dietary exposure (Pethybridge et al., 2010;Matulik et al., 2017). Since biomagnification depends on the structure and complexity of the food web (Wang, 2002), focusing on local shark assemblages, and performing stable isotope coupled with pollutant analyses, might delineate bioaccumulation patterns and better evaluate the extent of biomagnification in top-order predators, including elasmobranchs (Fisk et al., 2002;Domi et al., 2005). ...
We provided the first multi-species study investigating the presence and organotropism of trace elements in three tissues of 12 elasmobranch species. Shark species showed comparable TE loads, although milk sharks and juvenile scalloped hammerhead sharks exhibited the highest Cd and Hg levels, respectively. Fins accumulated higher levels of Pb, Co, and Cr; muscles higher V, As, and Hg; livers higher Se and Cd levels. The organotropism of TEs calls for cautious when choosing a tissue to be sampled since certain tissues, like fin clips, do not provide reliable surrogate for the internal loads of some TEs. Strong correlations between essential and toxic TEs indicated detoxification mechanisms, while the TMF provided evidence for Hg, As and Se biomagnification along the food-web.
Considering the difficulties in assessing elasmobranchs contamination from different areas, the proposed multi-species approach represents a valuable way to estimate the species-specific accumulation and transfer of pollutants in sharks.
... This is because blood is one of the first tissues to come into contact with and be affected by heavy metals or xenobiotics (e.g., pesticides), it is the primary carrier for these substances after uptake, and it is responsible for transporting the body's defense systems (e.g., antioxidants) in response to resulting tissue damage (Witeska, 2005;Sadauskas-Henrique et al., 2011;Javed and Usmani, 2015). Further, because red blood cells (RBCs) have a comparatively shorter life span relative to liver and muscle tissue, and sampling is minimally invasive relative to other tissues, WB may be a better and more accessible non-lethal marker of environmental Hg exposure (Amlund et al., 2007, de Castro Rodrigues et al., 2011, Mohmood et al., 2012, Matulik et al., 2017. ...
... In fishes, MeHg first crosses the gut after ingestion and then binds to RBCs before being transported via the circulatory system to other organs (e.g., liver, brain), readily crossing internal membranes, and is eventually stored in skeletal muscle where it binds to protein sulfhydryl groups (Wiener and Spry, 1996;Hoffman et al., 2002). This process, along with a relatively short biological life span for erythrocytes compared to tissues, allows for WB Hg to indicate recent Hg exposure (i.e.,~weeks to months), whereas Hg in liver and muscle indicate longer-term exposure (i.e., months to years) (Amlund et al., 2007;de Castro Rodrigues et al., 2011;Mohmood et al., 2012;Matulik et al., 2017) although the life span of Goliath Grouper erythrocytes is unknown and there is great variability in the life span of erythrocytes in fish from 13 to 500 days (Witeska, 2013). Therefore, we suspect inconsistencies in the relationships between THg and MeHg in blood and tissues may result from differences in biological life spans of RBCs relative to other tissues, different spatiotemporal Hg exposures, or physiological or environmental factors (Malinowski, 2019a;Malinowski et al., 2020). ...
Mercury (Hg) is a ubiquitous and non-essential heavy metal that is highly toxic to aquatic organisms. Few studies examine Hg and its effects on wild fish populations. Here, we investigated the potential effects of Hg exposure on a large and long-lived marine species of conservation concern, the vulnerable Atlantic Goliath Grouper Epinephelus itajara. Our objectives were (1) to measure Hg (methyl-Hg; and total Hg = combined methyl-Hg and inorganic-Hg) concentrations in whole blood (WB) and gametes (eggs and sperm); (2) to investigate the relationships between Hg concentrations in muscle and liver with WB and gametes; (3) to investigate the relationships between Hg concentrations in liver, muscle, and WB with hematological and plasma biochemical analytes; and (4) to investigate the relationship between liver Hg and pigmented macrophage aggregates in liver tissue sections. We found several lines of evidence for potential adverse effects on Goliath Grouper health and reproduction by high Hg concentrations in liver, muscle, WB, and gametes, including (1) Hg concentrations in all tissues and gametes were well above observable ranges of marine and freshwater fishes from experimental exposure studies; (2) gamete Hg concentrations were among the highest recorded in wild fishes, with seasonal patterns suggesting females offload significant amounts of Hg into their eggs during the spawning season; (3) Methyl-Hg was highest in muscle, followed by sperm, liver, eggs, and WB; (4) there were significant correlations between liver, muscle, and WB Hg concentrations with various blood analytes; (5) vitellogenin positively correlated with female liver methyl-Hg concentrations, and was abnormally high in males, suggesting direct endocrine effects; and (6) liver total Hg positively correlated with pigmented macrophage aggregate count and percent area. This work will help guide future research examining the potential adverse effects of Hg and its role as an additional stressor on wild fish populations.
... The absence of a temporal trend, with THg levels remaining elevated, in fishes of northeastern Florida Bay was recently supported by a survey of fish-eating osprey from 1998to 2008(1993: Strom and Graves 20012000-2002 Evans andRumbold unpublished;2006-2008Adams et al. 2018) Additionally, recent reports of exceptionally high THg in sharks (Matulik et al. 2017) and bottlenose dolphin (Tursiops truncates, Damseaux et al. 2017) However, common snook (Centropomus undecimalis) caught near the headwaters of Shark River Estuary (North Prong), while highly variable through the years (1993-2015; parsed in three-year periods; F ¼ 3.8, df ¼ 6, 68, p ¼ 0.002), did not exhibit a monotonic temporal trend in least square mean (LSM) for THg (1996-1998, 2007-2009 and 2013-215 were periods with elevated THg >1 mg/ kg for snook with a TL of 645 mm). ...
... leucas), sharpnose (Rhizoprionodon terraenovae) and tiger sharks (Galeocerdo cuvier) (for review, see Rumbold et al. 2014). Matulik et al. (2017) also found higher THg in sharks from Florida Bay as compared sharks caught years earlier by Adams et al. (2003). Furthermore, a research study (Reistad 2018) that sampled sharks in Charlotte Harbor in 2015 reported THg in juvenile blacktips (0.836 mg/kg) that was higher than the average level in slightly older blacktips (0.79 mg/kg, pool of juveniles and young adults) sampled from the area from 1989-2001 by Adams et al. (2003). ...
Mercury in Everglades food webs poses human health and ecological
risks most notably to anglers, hunters and fish-eating wildlife. These risks vary spatial and temporally across the Everglades landscape. The purpose of this chapter is to present an evaluation of temporal trends in mercury bioaccumulation within specific links in Everglades food webs. Emphasis is given to assessing temporal trends in biotically important species (see Chap. 8, Vol. II for food web descriptions of mosquitofish, largemouth bass, wading birds, and the Florida panther); however, multiple additional species along a gradient of trophic levels and habitats are considered in the context of the recognized high degree of spatial variability in bioaccumulation across the Everglades.
... Species belonging to the orders Carcharhiniformes and Lamniformes had the highest concentration of all four pollutants (Figs. 3 to 6). The variation observed between groups can be explained by the diversity of elasmobranchs, as well as their different habitats, size, age, trophic position, life strategies and diet (Pethybridge et al., 2010;Olin et al., 2014;Beaudry et al., 2015;Sandoval-Herrera et al., 2016;Matulik et al., 2017;McKinney et al., 2016;McMeans et al., 2015;Morris et al., 2016). Many shark species are migratory predators that feed continuously and as pollutants can vary across geographic regions, species may be exposed to pollutants in different ways (Teffer et al., 2014). ...
... trace elements) pollutants (Olin et al., 2014;Beaudry et al., 2015;Gilbert et al., 2015aGilbert et al., , 2015bWeijs et al., 2015;Cagnazzi et al., 2019). Elasmobranchs occupying high trophic positions also tend to be long-lived and large-sized, mature late, and have relatively few offspring, which allows for the bioaccumulation of pollutants (Fisk et al., 2002;Cagnazzi et al., 2019;Matulik et al., 2017;McKinney et al., 2016). As well as bioaccumulation, trophic level analysis (SI 1.10.) ...
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.
... As bioaccumulation and biomagnification of mercury in the trophic chain result in social, environmental, and human and animal health impacts (Matulik et al., 2017), the control, monitoring and remediation measures of this metal are essential to reduce such impacts (United Nations Environment Programme [UNEP], 2013). Review papers have proposed the use of nanotechnology and other methods for stabilization/solidification, immobilization, vitrification, thermal desorption, soil washing, electro-remediation, phytostabilization, phytoextraction, and phytovolatilization of mercury to remediate this metal (De et al., 2008;Wang et al., 2012Wang et al., , 2020. ...
... Mercury is one of the toxic metals that is a major concern for human health and its bioremediation aims to lower its concentration and consequently reduce its toxicity to the environment. Mercury methylation is an eminent risk for bioremediation because methylmercury is more strongly toxic to humans and has a greater biomagnification risk in the food chain due to its lipophilicity Matulik et al., 2017). The environmental conditions of wetlands favor mercury methylation by anaerobic microorganisms and, in a lesser extent, by aerobic Firmicutes (Gilmour et al., 2013) to produce methylmercury, which is more toxic than the other metal forms (Podar et al., 2015). ...
The quantification, efficiency, and possible mechanisms of mercury phytoremediation by endophytic bacteria are poorly understood. Here we selected 8 out of 34 previously isolated endophytic bacterial strains with a broad resistance profile to metals and 11 antibiotics: Acinetobacter baumannii BacI43, Bacillus sp. BacI34, Enterobacter sp. BacI14, Klebsiella pneumoniae BacI20, Pantoea sp. BacI23, Pseudomonas sp. BacI7, Pseudomonas sp. BacI38, and Serratia marcescens BacI56. Except for Klebsiella pneumoniae BacI20, the other seven bacterial strains promoted maize growth on a mercury-contaminated substrate. Acinetobacter baumannii BacI43 and Bacillus sp. BacI34 increased total dry biomass by approximately 47%. The bacteria assisted mercury remediation by decreasing the metal amount in the substrate, possibly by promoting its volatilization. The plants inoculated with Serratia marcescens BacI56 and Pseudomonas sp. BacI38 increased mercury volatilization to 47.16% and 62.42%, respectively. Except for Bacillus sp. BacI34 and Pantoea sp. BacI23, the other six bacterial strains favored mercury bioaccumulation in plant tissues. Endophytic bacteria-assisted phytoremediation contributed to reduce the substrate toxicity assessed in different model organisms. The endophytic bacterial strains selected herein are potential candidates for assisted phytoremediation that shall help reduce environmental toxicity of mercury-contaminated soils.
... THg is known to be almost exclusively in the MeHg form in shark and fish muscle (Bosch et al., 2016;de Carvalho et al., 2014;Pethybridge et al., 2010;Ruiz-de-Cenzano et al., 2014), including species sampled in this study (e.g. giant trevally and deepwater snapper (Sackett et al., 2015), bull shark (Matulik et al., 2017)). However, a subset of muscle samples from 10 bull sharks were analyzed for MeHg, specifically to verify that MeHg accounted for the majority of THg in our shark muscle samples and to evaluate the link between d 202 Hg values and Hg speciation. ...
... Since MeHg has higher d 202 Hg values compared to inorganic Hg (iHg) (Perrot et al., 2016), the decrease in MeHg fraction alongside the increase in iHg fraction in pilot whales was accompanied by a drop in d 202 Hg values (around 1‰ decrease) (Bolea-Fernandez et al., 2019). In our bull shark samples, MeHg accounted for 95% of total Hg, which is consistent with previous studies on this species (Matulik et al., 2017) or on other sharks (de Carvalho et al., 2014;Nam et al., 2011;Pethybridge et al., 2010). Moreover, no correlation was found between MeHg fraction and d 202 Hg or shark length (SI Figs. ...
... With a strictly coastal distribution, this shark inhabits both demersal and pelagic habitats, with a preference for warmer regions found in tropical, subtropical, and temperate areas (Ebert et al., 2021). Their inclination to inhabit coastal regions exposes them to heightened levels of contamination (Matulik et al., 2017). While the species generally favors shallow habitats, pregnant females may exhibit seasonal migratory behavior (Weigmann, 2016). ...
... When humans consume these fish, they ingest hazardous levels of mercury, which can lead to neurological damage and other health issues. Similarly, pesticides and industrial chemicals that enter water bodies can also undergo bioaccumulation and biomagnification, endangering marine species and also, human health (Azaman et al., 2015;Barón et al., 2015;Costa et al., 2020;Matulik et al., 2017;Ruelas-Inzunza et al., 2014;Signa et al., 2017;H. Wang et al., 2019). ...
... Hg is also discharged into the environment as a by-product of Hg mining, gold refining, fuel combustion, and instrument fabrication (Moreno et al., 2008). Hg bioaccumulation and biomagnification in the trophic chain have consequences for society, the environment, and human and animal health (Matulik et al., 2017). Endophytic bacteria Bacillus amyloliquefaciens of Eleusine indica and Jeotgalicoccus huakuii of Cynodon dactylon are employed for phytoremediation of Hgcontaminated soil due to their high siderophore synthesis and absence of hemolysis (Ustiatik et al., 2021). ...
... As for Hg concentrations, the highest average concentrations were found in the protein group rather than in carbohydrates, unlike for MeHg (Fig. 4d). Fish was again the protein with the highest concentration values, probably due to the bioaccumulation and biomagnification effect widely described for this food matrix [28]. Meanwhile, for the carbohydrate group, the highest Hg concentration occurred in cassava, whereas a strong variation can be seen in yam, evidencing similar concentrations in both matrices for some localities (Fig. 4e e f). ...
Mercury (Hg), and its different chemical forms, such as methylmercury (MeHg), are highly toxic compounds that affect the environment as well as human and animal health. Specifically, mining practices may cause these metals to be present in water, air, soil, and food. This study examines the concentration levels of Hg and MeHg in locally-consumed foodstuffs, including fish, pork, chicken, yam, plantain, and cassava, in a specific region of Antioquia (Colombia) by assessing the toxicological risk to the population due to the exploitation of open-pit alluvial mining in the area. Among foods examined, the highest amount of Hg was found in fish > pork > chicken > cassava > plantain > yam (ranging from 207.87 to 0.23 μg/g). Conversely, MeHg was identified in cassava > fish > plantain > chicken > yam > pork in amounts ranging from 1.567 to 0.434 μg/g. The risk exposure factors of the acceptable daily intake (ADI) and the provisional tolerable weekly intake (PTWI) for Hg and MeHg exhibited a trend similar to the amount of metal in the assessed foods. This work contributed to characterizing and preventing public health problems in a mining population in the Bajo Cauca region of Antioquia, which requires special attention due to their potential exposure to Hg and MeHg through the most locally consumed foods.
... Total mercury is known to biomagnify in marine ecosystems (Lavoie et al., 2013;McKinney et al., 2016;Matulik et al., 2017) and the results from the present study further confirms this, as species in higher trophic positions accumulated higher concentrations of THg compared to species in lower trophic positions. A really good example of biomagnification in the present study, was between the four ray species where the shortfin devil ray and longhorned mobula feeding on zooplankton had the lowest concentrations, followed by the Oman cownose ray feeding on invertebrates and molluscs, with the highest concentrations in the bull ray that feeds on molluscs and teleost fish. ...
Global declines in elasmobranch populations resulting from several stressors raises conservation concern. Additionally, apex predators bioaccumulate high concentrations of total mercury (THg), due to biomagnification. Although South Africa is considered one of the top ten contributors of Hg emissions globally, information on Hg concentrations in elasmobranchs is limited. The aim of this study was to evaluate the THg concentrations in 22 species of elasmobranchs along the South African coastline. Concentrations ranged between 0.22 and 5.8 mg/kg in Haploblepharus pictus (dark shysharks) and Rostroraja alba (white skates) on the south coast, respectively. Along the east coast it ranged between 0.21 and 17.8 mg/kg in Mobula kuhlii (shortfin devil rays) and Sphyrna lewini (scalloped hammerheads), respectively. Mercury concentrations on the east coast were in the same range or higher compared to the same species sampled between 2005-10 from the same region, with generally higher concentrations compared to the same species sampled globally.
... Contaminated producers are consumed by predators, increasing chemical concentrations further down the food chain. The pattern repeatedly continues, with biomagnification occurring as animals at higher levels in the food chain accumulate more chemicals (Matulik et al., 2017;Zenker et al., 2014). The compound must be long-lived, mobile, soluble in lipids, and biologically active for bioaccumulation and biomagnification to occur and induce detrimental effects in animals and humans (Peng et al., 2017). ...
The kinetics and mechanism of methylene blue and Congo red adsorption by carbonized and chemical activated Cassia fistula was investigated for various physicochemical parameters in a batch system. The adsorbents were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). The results showed that the adsorbents were rich in carbon content and heterogeneous large surface area for organic dye interaction. T understand the adsorption process, the equilibrium data was tested using Langmuir, Freundlich, Temkin and Brunauer-Emmett-Teller (BET) adsorption isotherms. The good physisorption adsorption process is indicated by the Freundlich constant, n>1. Furthermore, -0.0188, 0.0007, and 0.6990 for methylene blue; -0.0692, 0.0001 and 0.3856 for Congo red were obtained for ∆G0, ∆H0 and ∆S0 thermodynamics parameters, respectively. Results from BET study revealed efficient dye adsorption and chemical activation of the adsorbent with hydrogen peroxide and potassium hydroxide. The regression coefficient (R2) of carbonized and chemical activated Cassia fistula biomass were: 0.918, 0.742, and 0.878, for methylene blue; 0.708, 0.666 and 0.527 for Congo red at 60 °C. Results from adsorption studies proved that chemical-activated adsorbent from Cassia fistula pods is a promising effective and eco-friendly alternative for the removal of organic dyes from the aqueous system.
... In the North Western Mediterranean Sea, swordfish are able to cross long distances in a short time, and appear to prefer different habitats for breeding and feeding (Canese et al., 2008), in which they may spend long periods (Orsi Relini et al., 2003). Being one of the larger top predators, the swordfish is susceptible to accumulating high levels of contaminants, particularly mercury (Hg), both by biomagnification up the food web as well as by bioaccumulation during its life span (Storelli and Marcotrigiano, 2001), as has been observed in other top predators (Pethybridge et al., 2012;Matulik et al., 2017;Biton-Porsmoguer et al., 2018). Increasingly high concentrations of Hg in Mediterranean seafood are a worrying seafood safety issue due to the major toxic effects of its organic form, methylmercury (MeHg) (Cossa et al., 2009). ...
Studies integrating trophic ecology, physiological condition and accumulation of heavy metals in top predators, such as swordfish, are needed to better understand the links between them and the risk to humans associated with consumption of these fish. This research focuses on the swordfish of the Catalan Sea and follows a multi method approach that considers their diet, their liver lipid content, and mercury accumulation in their bodies as well as in their prey. The aim is to highlight the links between trophic ecology, physiology (fish condition), and eco-toxicology. Results indicate that poor condition of swordfish based on size and the levels of lipid in the liver, and the high Hg levels accumulated to the trophic web (particularly from cephalopods) may indicate potential unfavourable feeding and reproduction conditions for swordfish in the NW Mediterranean and that this warrants further investigation.
... These have generated a concern about human health risks to shark consumption, leading this distress as a conservation strategy to reduce shark fin demand (WHO, 2006;Escobar-Sánchez et al., 2010;Fabinyi and Liu, 2014;Man et al., 2014;Nalluri et al., 2014). The main concern is because THg is toxic for humans as it is a cumulative poison that bioaccumulates in the body (Matulik et al., 2017). Because THg is biomagnified by trophic transfers in food webs, top predators such as sharks, generally show very high THg concentrations in their tissues in comparison to other seafood products (Nalluri et al., 2014). ...
Sharks are fished for human consumption in Colombia, and fins are exported illegally to international markets. The goal was to identify differences in total mercury (THg) concentrations in fins and muscles of shark species seized in the Buenaventura port (Colombian Pacific), and to assess potential human health risks related to shark consumption. Seven species were considered in this study: Pelagic Thresher (Alopias pelagicus), Pacific Smalltail Shark (Carcharhinus cerdale), Brown Smoothhound (Mustelus henlei), Sicklefin Smoothhound (Mustelus lunulatus), Scalloped Bonnethead (Sphyrna corona), Scalloped Hammerhead (Sphyrna lewini), and Bonnethead Shark (Sphyrna tiburo), and THg was analyzed in shark tissues. 24% muscle samples concentrations were above international recommended limits for human consumption, especially for A. pelagicus and S. lewini. Stable isotopes (δ¹³C and δ¹⁵N) analysis showed a foraging overlapping in coastal habitats, where overfishing usually occurs. This study provides useful scientific information to develop management plans for sharks in Colombia and neighboring countries.
... Mercury is the sixth most copious toxic element discharged in different speciation states as a pollutant in soil, water, and air. The organic speciation state of mercury is most hazardous than ionic and atomic speciation states as it can move across the plasma membrane with ease and interact with thiol groups of enzymes besides getting bioaccumulated (Beauvais-Flück et al., 2016;Matulik et al., 2017). Organic mercurials are 100 times more toxic to living beings than ionic speciation state of mercury (Jan et al., 2009). ...
Organomercury is the most toxic biomagnifiable state of mercury, and to date, no natural organomercurial detoxification mechanism is encountered in plants. Bacterial merB gene encoding organomercury lyase show low expression in transgenic plants. For ideal expression, a synthetic merBps gene possessing143 out of 213 codons discrete from native merB gene from Escherichia. coli was fabricated based on codon usage in tobacco. Through Agrobacterium-mediated transformation, the merBps gene got successfully integrated into tobacco. Of several putative merBps transformants selected with 200 μg ml-1 kanamycin, only ∼45% were PCR positive for both nptII and merBps genes. Healthy and vigorously growing shoots of few PCR-positive putative transgenic lines were multiplied and rooted. After transplantation and acclimatization, the resultant plants flowered and fruited in pots. Southern analysis revealed the presence of a single copy of the merBps gene in four lines. RT-PCR and Western investigations established successful transcription and translation of the merBps gene in these transgenic lines, respectively. Fabrication of fully functional organomercury lyase in merBps transgenic lines was established based on the potential of their (i) seeds to germinate; (ii) shoots to grow and multiply; and (iii) leaf disc to remain green, even in the presence of 4 nmole ml-1 phenylmercuryacetate (PMA) while the wild type was susceptible to even 1 nmole ml-1 PMA. These findings confirmed that the synthetic merBps gene could be effectively expressed in plants and exploited for remediation of organomercurial contaminated sites.
... A growing concern about the negative effects of pollution in sharks is noted, as these animals are apex predators and, in addition to bioaccumulation concerns, certain elements also display the ability to biomagnify through the food chain, leading to risks concerning this group (Escobar-Sánchez et al., 2011;Olmedo et al., 2013;Matulik et al., 2017). Studies indicate that non-essential metallic elements displaying potential toxicity accumulate mainly in shark liver and muscle tissue (Terrazas-López et al., 2016), although other organs, such as gonads, gills, kidneys, rectal gland and brain, can also undergo bioaccumulation processes (Frías-Espericueta et al., 2014;Gilbert et al., 2015;Wosnick et al., 2021). ...
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.
... Previous studies have noted significant relationships between life stage and metal bioaccumulation (Maz-Courrau et al., 2012;Terrazas-López et al., 2016;Matulik et al., 2017). However, these results may be more related to animal size rather than age/life stage itself. ...
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.
... In the particular case of sharks in Mexico, there are slightly more specific studies that address more detailed topics, ranging from the characterization of Hg concentrations in the different organs of several species (Ruelas-Inzunza and Páez-Osuna 2005;Maz-Courrau and López-Vera 2006;Cai et al. 2007;García-Hernández et al. 2007;Hurtado-Banda et al. 2012) to the association with methylmercury (MeHg or CH 3 Hg + ) (Matulik et al. 2017), and studies on the Se/Hg ratio (Escobar-Sánchez 2010;Escobar-Sánchez et al. 2010;Pancaldi et al. 2019). Other studies have focused on the concentration profiles of toxic elements, mainly in tissues, to associate them with states of stress (Barrera-García 2013; Mendoza-Díaz et al. 2013;Frías-Espericueta et al. 2014). ...
Given their predatory characteristics, long life, and high trophic levels, sharks can have a remarkable ability to bioaccumulate and/or biomagnify trace elements (TE). In the present study, 13 TE (Hg, Pb, Cd, Cu, As, Se, Zn, Cr, V, Fe, Ni, Co, and Mn) were analyzed in the muscle tissue of three shark species (Prionace glauca, Carcharhinus falciformis, and Alopias pelagicus) using high-resolution mass spectrometry inductively coupled to a plasma generator (HR-ICP-MS); 30 shark specimens of each specie were obtained during commercial fish landings in the port of Manzanillo, Mexico. The morphometric characteristics and sex of the sharks were recorded. Shark A. pelagicus accumulated higher concentrations of TE, especially for Hg and Cd, than the other species. Significant differences in the TE levels were detected between sexes in P. glauca and A. pelagicus; in all cases, the highest concentrations were found in female muscle tissue. The ability of sharks to bioaccumulate ETs depends of the metals (essentials higher than non-essential) but is explained mainly by feeding habits associated to sexes (population segregation) and size (ontogeny). The association between TE in shark specimens was related to the essentiality, their antagonistic action, and origin. The Se/Hg ratio was significantly higher than 1, evidence of the protective role of dietary Se against Hg uptake and toxicity in all specimens of the three shark species. Also, the elevate inverse correlation of As and Cd versus Se could indicate a protective action of Se against these toxic metals, but the mechanism must be investigated.
... A notable finding was the elevated metal concentrations in Caribbean reef sharks, particularly THg, relative to the other larger-bodied species sampled and values reported for other coastal sharks sampled from neighboring regions (see Table 2). Species-specific differences in bioaccumulation trajectories of toxicants have been reported in sharks 12,50 , whereby variable physiologies, trophic ecologies, and maternal offloading may influence the initial concentrations and subsequent bioconcentration 42,51 . One explanation for the generally high metal concentrations in Caribbean reef sharks could be ascribed to a piscivorous diet in larger individuals, foraging upon predominantly larger coral reef-associated fishes (e.g., Grouper, Snapper, and Barracuda), which exhibit The median sizes of sharks sampled was 162 cm for Caribbean reef sharks* and 301 cm for tiger sharks. ...
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.
... However, S. entomon is a large benthic isopod that predates on other species of benthic fauna (Leonardsson, 1991). Higher concentrations of Hg in relation to other benthic species is therefore expected due to biomagnification (Matulik et al., 2017), as well as a higher δ 15 N (Mustamäki et al., 2014). ...
Unexpected increasing trends in the concentration of contaminants in European perch (Perca fluviatilis) and in activity of ethoxyresorufin-O-deethylase (EROD) in European perch and eelpout (Zoarces viviparus) have been observed at a Swedish coastal reference site. This study uses data from different sources to investigate plausible explanations. The results showed that a change in diet and an improved overall condition coincide with an increase in mercury in European perch. Furthermore, an increase in several organic contaminants in European perch coincided with the introduction of an invasive deep-burrowing polychaete, which likely contributed to the release of contaminants through bioturbation. The increase in EROD-activity in both species seems to be related to contaminants that reach the fish through the water rather than the diet. The results show that for contaminants that are taken up via the diet, trends in contamination can be opposite for different species of fish in the same area.
... This form of organic Hg (RHg + ) is bioacumulative in nature as it can readily pass the biological membrane and accumulates in the cells and its concentration increases at every trophic level making the problem more severe (Siudek et al., 2011;Beauvais-Flück et al., 2016). It finally accumulates in the various aquatic animals of the food chain, entering into humans as a food source and this becomes the most common way of Hg exposure in our bodies (Gomes et al., 2014;Velásquez-Riaño and Benavides-Otaya, 2016;Matulik et al., 2017). Globally, methyl Hg has been detected in fish and other seafood throughout the world (Green et al., 2010;Peng et al., 2016). ...
... Furthermore, the inclusion of stomach content analysis when assessing the energetic state of wild elasmobranch populations should allow researchers to more easily delineate which fluctuations in plasma metabolites are the result of feeding and which are the result of other potentially influential factors(Zammit and Newsholme 1979;de Roos 1994;Wood et al. 2010).Finally, studies investigating the potential effects of urbanization on elasmobranch energy storage and metabolism should consider evaluating concentrations of pollutants, toxins, or heavy metals in the tissue of elasmobranchs and exploring the relationship of such contaminants with body condition and plasma metabolite concentrations. While it is well established that high levels of some contaminants can accrue in elasmobranch tissue, the long-term consequences of such accumulation on physiology and energy storage and metabolism remains unknown(Matulik et al. 2017).Additionally, future research exploring urbanization and elasmobranch energy storage and metabolism may benefit from utilizing BRUVS (Baited Remote Underwater Video Survey) to thoroughly assess the prey base in sampling locations subject to varying degrees of urbanization.This thesis offers the first comprehensive assessment of intrapopulation variation in nurse shark body condition and plasma metabolite concentrations, including the first measurements of plasma ketone bodies in wild nurse sharks. Results reveal that relationships between and among body condition and plasma metabolite concentrations are highly dependent on shark sex and life stage and, that sexual and seasonal variation of some of these metrics occurs in mature nurse sharks, contributing to the current knowledge base of nutritional and energy metabolism of wild-sampled elasmobranchs. ...
The way an animal utilizes and stores energy directly affects its ability to perform essential life functions (e.g. foraging, migration, reproduction), with implications for its health and fitness; therefore, individual variation in energy storage and metabolism within a population leads to intra-population variation in individual fitness and survival. Consequently, understanding the factors that contribute to variation in energy storage and metabolism within a population can aid in identifying factors that influence that population’s fitness. Compared to other taxa, there has been relatively little research to investigate the factors that govern variation in elasmobranch energy use and storage, particularly in wild populations. Furthermore, there has been almost no research conducted to explore how urbanization, a growing threat to marine ecosystems and organisms, affects elasmobranch energy storage and metabolism and, ultimately, their health and fitness. To address this knowledge gap, morphological (i.e. body condition) and biochemical (i.e. plasma cholesterol, free fatty acid, triglyceride, and ketone body concentrations) metrics related to energy storage and utilization were measured for 118 wild-sampled south Florida nurse sharks (Ginglymostoma cirratum). Statistical analyses were performed to identify any correlations between metrics and explore ontogenetic, sexual, seasonal, and spatial variation in body condition and plasma metabolite concentrations within the population. Results demonstrated that several metrics can be significantly linearly correlated with one another, but these relationships are highly dependent on nurse shark life stage and sex. The mean plasma metabolite concentrations for immature, mature female, and mature male nurse sharks was not significantly different; however, mature female nurse sharks had significantly higher body condition than mature male sharks. Further analysis revealed that this difference is driven by seasonal variation in mature female body condition, likely related to the accumulation of energy stores prior to reproduction. Significant seasonal variation also occurred in plasma concentrations of β-hydroxybutyric acid for mature male nurse sharks, possibly related to energetically exhausting mating activity during the wet season. Significant spatial variation occurred in the plasma concentrations of both triglycerides and free fatty acids for immature nurse sharks. Immature nurse sharks sampled within the more urbanized Metropolitan zone had higher mean triglyceride concentrations, and lower mean free fatty acid concentrations, than their conspecifics sampled within the relatively more natural National Park zone; this may imply that nurse sharks in the Metropolitan zone are feeding more, or more frequently, than nurse sharks in the National Park zone. The results of this thesis contribute to the growing knowledge base on energy storage and metabolism in wild-sampled elasmobranchs, as well as provide the first exploration of variation in elasmobranch body condition and plasma metabolites relative to urbanization, an anthropogenic threat with the capacity to influence elasmobranch fitness and survival.
... Mercury can be bioaccumulated at all levels of trophic chains [8]. Due to the specific properties of mercury (bioconcentration and biomagnification) [9], it became necessary to develop new types of reference materials, which will be a tool for obtaining reliable analytical information. ...
Reference materials (RMs) play an important role in all elements of the quality assurance system of measurements. In this work, ``package'' 4 new CRMs (bottom sediment, herring tissue, cod tissue, cormorant tissue) were prepared and characterised to carry out the quality control in monitoring analysis of mercury and methylmercury in environmental samples. Materials - candidates were collected in Poland and south part of the Czech Republic. All materials were freeze-dried, milled, sieved, homogenised, sterilized and distributed in amber bottles. For the homogeneity and stability study of the samples of materials several statistical tests were applied. Materials - candidates for CRMs with certified mercury and methylmercury content meet the heterogeneity requirement and can be considered homogenous both between bottle and within bottle. Each material meets also the requirements for the stability condition of reference material with certified mercury content.
... The concentrations of MeHg in a predatory fish can reach 6 magnitudes of order higher compared to ambient seawater (WHO, 1990). MeHg is the dominant form of total Hg pool, especially in high trophic levels (Matulik et al., 2017;Forsyth et al., 2004). Since Hg is a lipophilic metal, it can readily accumulate in phospholipid bilayer of cell membranes, while MeHg concentrates mainly in cytosol (Mason et al., 1995). ...
In response to the current environmental crisis, this study focuses on converting biowaste into phosphorus-oxygen-rich activated hydrochar (AH) for removing persistent pollutants such as Diclofenac (DCF) and chromium (VI) (Cr (VI)) from polluted water. The AH was prepared via hydrothermal carbonization of argan nut shells followed by H3PO4 activation under an oxygen-rich atmosphere. The obtained AH was characterized by a high specific surface area of 1879 m2g−1, remarkable mesoporosity, and wide pore diameters. The AH was further analyzed revealing its highly aromatic nature, as well as the abundance of phosphorus and oxygen functional groups on its surface. These properties led to high adsorption capacities of diclofenac and chromium (VI) of 240 mgg−1 and 539 mgg−1, respectively. The investigations indicated that the AH applied physical and chemical forces for removing Cr (VI), while the uptake of DCF molecules was governed by physical forces. Indeed, the high aromaticity and oxygen functionality of AH facilitated the DCF adsorption through hydrogen bonding, π-π interactions, and pore-filling. Meanwhile, the oxygen functionality and the oxygen and phosphorus electron-providing sites on the AH’s surface favor the removal of Cr (VI) ions through physical and chemical interactions, including electrostatic attractions, ion exchange, complexation, and oxidation–reduction reactions. These findings highlight the effectiveness of AH in the elimination of DCF and Cr (VI) from polluted water.
An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention’s progress to reduce the impact of global Hg pollution on people and the environment.
As human activities release increasingly more fossil fuel-derived emissions directly into the atmosphere, terrestrial, aquatic, or marine ecosystems, the biomagnification and bioaccumulation of toxic metals in seafood is an ever more pressing concern. As apex predators, sharks are particularly susceptible to biomagnification and bioaccumulation. The consumption of shark fin is frequent throughout Asia, and their ingestion represents a pathway through which human exposure to potentially unsafe levels of toxic metals can occur. Shark fins processed for sale are difficult, if not impossible to identify to the species level by visual methods alone. Here, we DNA-barcoded 208 dried and processed fins and in doing so, identified fourteen species of shark. Using these identifications, we determined the habitat of the shark that the fin came from and the concentrations of four toxic metals (mercury, arsenic, cadmium, and lead) in all 208 samples via inductively coupled plasma mass spectrometry. We further analyzed these concentrations by habitat type, either coastal or pelagic, and show that toxic metal concentrations vary significantly between species and habitat. Pelagic species have significantly higher concentrations of mercury in comparison to coastal species, whereas coastal species have significantly higher concentrations of arsenic. No significant differences in cadmium or lead concentrations were detected between pelagic or coastal species. Our results indicate that a number of analyzed samples contain toxic metal concentrations above safe human consumption levels.
As a consequence of urbanization and industrialization, the environment is progressively polluted with heavy metals which is a problem of great concern. In plants it can create oxidative stress, ethylene production, chlorosis, Necrosis, stunted growth, inhibits various physiological processes, and decrease biomass. Due to their persistent and non-degradable nature, they enter the food chain leading to biomagnification and causing carcinogenic, mutagenic, and lethal effects on humans and animals. Bioremediation, phytoremediation, biotransformation, non-host inoculation, and other methods are used to treat heavy metals in the environment. Endophytic bacteria have gained attention for their potency to remove or immobilize heavy metals. Bacterial bioremediation is an effective and reliable technique to degrade, detoxify, mineralize, transform, or reduce the concentration of pollutants. This review helps in understanding the endophytic bacterial activity on bioremediation along with its plant growth-promoting properties.
Marine pollution, due to the regular discharge of contaminants by various anthropogenic sources, is a growing problem that imposes detrimental influences on natural species. Sharks, because of a diet based on smaller polluted animals, are exposed to the risk of water contamination and the subsequent bioaccumulation and biomagnification. Trace elements are very diffuse water pollutants and able to induce oxidative stress in a variety of marine organisms. However, to date, studies on sharks are rather scarce and often limited to mercury. In this context, the present study aimed to analyze the accumulation of trace elements and their putative correlation with the onset of an oxidative status in the muscle of the lesser spotted dogfish Scyliorhinus canicula, from the Central Mediterranean Sea. Ecotoxicological analysis detected the presence of Pb, As, Cd, Mn, Zn, Ni, Cu, and Fe; no significant differences were observed between sexes, while a negative correlation was found between Pb and animal length. Analysis of oxidative stress markers showed either positive or negative correlation with respect to the presence of trace elements. Lipid peroxidation (TBARS) positively correlated with Zn, Ni, and Fe; SOD enzyme activity negatively correlated with Cu and Ni; LDH was negatively correlated with Fe and positively correlated with Pb. Moreover, positive correlations between the leukocyte count and Mn and Zn, as well as with LDH activity, were also observed. The data suggested that, in sharks, trace elements accumulation may affect oxidant and antioxidant processes with important outcomes for their physiology and health.
Las partículas resultantes de las actividades humanas dentro de una cuenca
hidrográfica acumulan metales en el sedimento de los cuerpos hídricos
receptores. Una concentración excesiva de estos metales se puede relacionar
con niveles altos de toxicidad en prejuicio del ambiente. El objetivo de este
estudio es cuantificar la concentración de mercurio en el sedimento de la
subcuenca transfronteriza del río Suches (Perú y Bolivia) y así evaluar su
calidad al compararlos con los valores guía de calidad para sedimento. Cuatro
puntos de colecta fueron determinados a lo largo de la cuenca alta y media del
Suches durante la época de lluvias. Las muestras fueron procesadas en una
digestión ácida, el resultante fue analizado por un espectrómetro de emisión
atómica acoplado a un inductor de plasma (ICP-AES). Las concentraciones
muestran que los puntos cercanos a la laguna Suches (cuenca alta)
presentan los valores más altos (0,46 mg/kg) y los puntos más alejados
concentraciones de 0,06 mg/kg o menores. Los índices de contaminación
(factor de contaminación e índice de geoacumulación) demostraron que
el sedimento, más cercano a la laguna está altamente contaminado. Sin
embargo, esta condición va mejorando cuando nos alejamos de estos
puntos (aguas abajo). En conclusión, la calidad del sedimento ubica los
valores de la cuenca alta como plausibles de toxicidad con el ecosistema y
consecuentemente con la salud pública.
The bull shark (Carcharhinus leucas Valenciennes, 1839) is a large, primarily coastally distributed shark famous for its ability to penetrate far into freshwater bodies in tropical, subtropical, and warm-temperate climates. It is a cosmopolitan species with a geographical range that includes the coastlines of all major ocean basins (Atlantic Ocean, Indian Ocean, Pacific Ocean). As a consequence, freshwater occurrences of C. leucas are possible everywhere inside its geographic range. Carcharhinus leucas is a fully euryhaline, amphidromous species and possibly the widest-ranging of all freshwater tolerating elasmobranchs. This species is found not only in river systems with sea access that are not interrupted by human impediments but in hypersaline lakes as well. Rivers and estuaries are believed to be important nursery grounds for C. leucas, as suggested by observations of pregnant females in estuaries and neonates with umbilical scars in rivers and river mouths. Due to the physical capability of this species to enter riverine systems, the documentation of its occurrence in fresh and brackish water is essential for future conservation plans, fishery inspections, and scientific studies that focus on the link between low salinity habitats, shark nurseries, and feeding areas. The author’s review of the available literature on C. leucas revealed the absence of a comprehensive overview of fresh and brackish water localities (rivers and associated lakes, estuaries) with C. leucas
records. The purpose of this literature review is to provide a global list of rivers, river systems, lakes, estuaries, and lagoons with records and reports of this species, including a link to the used references as a base for regional, national, and international conservation strategies. Therefore, the objective of this work is to present lists of fresh and brackish water habitats with records of C. leucas as the result of an extensive literature review and analysis of databases. This survey also took into account estuaries and lagoons, regarding their function as important nursery grounds for C. leucas. The analysis of references included is not only from the scientific literature, but also includes semi-scientific references and the common press if reliable. The result of 415 global fresh and brackish water localities with evidence of C. leucas highlights the importance of these habitats for the reproduction of this species. Moreover, gaps in available distribution maps are critically discussed as well as interpretations and conclusions made regarding possible reasons for the distribution range of C. leucas, which can be interpreted as the result of geographic circumstances, but also as a result of the current state of knowledge about the distribution of this species. The results of the examination of available references were used to build a reliable and updated distribution map for C. leucas, which is also presented here.
Rapid population growth, urbanisation and industrialisation have caused serious problems in terms of water pollution and the supply of safe water. Solutions for monitoring pollutants in water and for removing them are urgently needed and they must be both efficient and sustainable.
Recent advances in emerging environmental nanotechnologies provide promising solutions for these issues. The physical and chemical properties of nanomaterials can be tailored by controlling attributes such as their size, shape, composition, and surface, so that they can be both highly specific and highly efficient. This makes them perfect platforms for a variety of environmental applications including sensing, treatment and remediation.
Providing an array of cutting-edge nanotechnology research in water applications, including sensing, treatment, and remediation, as well as a discussion of progress in the rational design and engineering of nanomaterials for environmental applications, this book is a valuable reference for researchers working in applications for nanotechnology, environmental chemistry and environmental engineering as well as those working in the water treatment industry.
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.
The twilight zone contains the largest biomass of the world’s ocean. Identifying its role in the trophic supply and contaminant exposure of marine megafauna constitutes a critical challenge in the context of global change. The white shark (Carcharodon carcharias) is a threatened species with some of the highest concentrations of neurotoxin methylmercury (MeHg) among marine top predators. Large white sharks migrate seasonally from coastal habitats, where they primarily forage on pinnipeds, to oceanic offshore habitats. Tagging studies suggest that while offshore, white sharks may forage at depth on mesopelagic species, yet no biochemical evidence exists. Here, we used mercury isotopic composition to assess the dietary origin of MeHg contamination in white sharks from the Northeast Pacific Ocean. We estimated that a minimum of 72% of the MeHg accumulated by white sharks originates from the consumption of mesopelagic prey, while a maximum of 25% derives from pinnipeds. In addition to highlighting the potential of mercury isotopes to decipher the complex ecological cycle of marine predators, our study provides evidence that the twilight zone constitutes a crucial foraging habitat for these large predators, which had been suspected for over a decade. Climate change is predicted to expand the production of mesopelagic MeHg and modify the mesopelagic biomass globally. Considering the pivotal role of the twilight zone is therefore essential to better predict both MeHg exposure and trophic supply to white sharks, and effectively protect these key vulnerable predators.
The twilight zone contains the largest biomass of the
world’s ocean. Identifying its role in the trophic supply and
contaminant exposure of marine megafauna constitutes a critical
challenge in the context of global change. The white shark
(Carcharodon carcharias) is a threatened species with some of the
highest concentrations of neurotoxin methylmercury (MeHg)
among marine top predators. Large white sharks migrate seasonally
from coastal habitats, where they primarily forage on pinnipeds, to
oceanic offshore habitats. Tagging studies suggest that while
offshore, white sharks may forage at depth on mesopelagic species,
yet no biochemical evidence exists. Here, we used mercury isotopic
composition to assess the dietary origin of MeHg contamination in
white sharks from the Northeast Pacific Ocean. We estimated that a
minimum of 72% of the MeHg accumulated by white sharks originates from the consumption of mesopelagic prey, while a maximum
of 25% derives from pinnipeds. In addition to highlighting the potential of mercury isotopes to decipher the complex ecological cycle
of marine predators, our study provides evidence that the twilight zone constitutes a crucial foraging habitat for these large predators,
which had been suspected for over a decade. Climate change is predicted to expand the production of mesopelagic MeHg and
modify the mesopelagic biomass globally. Considering the pivotal role of the twilight zone is therefore essential to better predict
both MeHg exposure and trophic supply to white sharks, and effectively protect these key vulnerable predators.
The toxicity of mercury (Hg), is generally known, and around 90% of Hg exist as methylmercury (CH3Hg⁺) in marine organism. Mercury concentrates in sharks and whales, which are at the top of the food chain as predators to cephalopods. The concentrations of Hg in liver and muscle of blue shark, caught in Sagami Bay, and in digestive gland and mantles of Todarodes pacificus, Sepia madokai, and Uroteuthis edulis caught in East China Sea were measured and analyzed. The Hg concentrations in the sharks, squids, and cuttlefishes determined in this study were almost same as those in the other sea regions. In addition, the Hg concentration in the blue shark was higher in the muscle than in the liver. In S. madokai and U. edulis, Hg accumulated in the digestive gland but not in the mantle. Although the Hg concentration in the digestive gland of T. pacificus is lower than those of S. madkai and U edulis, Hg concentration in the mantle is critically higher. More than 90% of Hg is present as CH3Hg⁺ in muscle of blue shark and mantle of T. pacificus. This feature is explained due to amino acids with the thiol groups and chain genes in the muscle of blue shark as well as in the mantle of T. pacificus. Myosin in the mantle of T. pacificus and blue shark enhances the stability of CH3Hg⁺. The amount of Hg in the digestive gland of T. pacificus could be too large to store; thus, Hg is released to the mantle, whereas the nutrients in the digestive gland of T. pacificus are supplied to other tissues. It is considered that the muscle fiber of T. pacificus is strong; therefore, large amounts of myosin levels may be present in T. pacificus than in S. madokai and U. edulis.
There is a global lack of data concerning shark consumption trends, consumer attitudes, and public knowledge regarding sharks. This is the case in Trinidad and Tobago, where shark is a popular culinary delicacy. A Knowledge, Attitudes, and Practices (KAP) survey was conducted in Trinidad and Tobago. Six hundred and seven questionnaires were administered. Univariate and stepwise multivariate logistic regressions were performed to test the association between KAP and demographic categories. The response rate was 93.4% with 567 questionnaires returned (473 from Trinidad and 94 from Tobago). Two hundred and seventeen (38.3%) participants were knowledgeable, 422 (74.4%) displayed attitudes in favour of shark conservation and sustainable use, and 270 (47.6%) displayed practices promoting shark conservation and sustainable use. Island (AOR = 2.81, CI = 1.78, 4.46) and tertiary education (AOR = 2.31, CI = 1.20, 4.46) significantly influenced knowledge level. Gender (AOR = 1.50, CI = 1.02, 2.20) and island (AOR = 0.56, CI = 0.35, 0.90) significantly influenced attitude. Gender (COR = 1.59, CI = 1.14, 2.22) was significantly associated with practices. Over 70% of respondents ate shark, and 54.7% ate shark infrequently enough to avoid risks from heavy metal toxicity. Our results may be useful to develop public awareness and practice improvement initiatives in order to improve KAP regarding shark meat consumption.
This study explored biogeochemical processes controlling the distribution of mercury (Hg) species in two lagoons with different pollution and eutrophication conditions in southwestern Taiwan. The eutrophication and pollution levels were higher in the Dapeng Bay than in the Chiku Lagoon, engendering a higher particulate Hg concentration and enrichment factor in the Dapeng Bay. The concentration range of total dissolved Hg (HgTD) and reactive Hg (HgR) was comparable between the lagoons, but the concentration of particulate Hg (HgP) was higher in the Dapeng Bay. HgR and HgTD abundance was primarily controlled by the availability of dissolved oxygen (DO) and biological absorption. In addition to pollution (which elevated HgP concentration), biological absorption and/or adsorption rather than lithogenic processes more likely regulated the HgP concentration. The effect of Hg pollution may superimpose on that of DO on the distributions of HgR and HgTD and may enhance HgP formation in the Dapeng Bay.
Mercury (Hg) in fish and aquatic products is a potential threat to human health and international trade, and guidelines of international advisory bodies are established for assessing Hg in these foods. As fish are the most consumed animal protein in Sri Lanka, this assessment summarises for the first-time total mercury concentrations in Sri Lankan marine and freshwater fish, invertebrates, aquatic plants, and fisheries products. It reveals that Hg levels in fish and other edible aquatic species are mostly below the published safety limits, except for certain top trophic level fish (swordfish, tuna, marlin). The review also highlights gaps in Sri Lankan Hg assessments such as a total lack of data for methyl‑mercury in these aquatic species and food products. This data compilation and assessment will serve as an initial baseline for comparison with results from future monitoring and research studies in Sri Lanka while adding to the world-wide Hg database.
The purpose of this chapter is to provide information to resource managers about current ecological risk from mercury exposure to fish and wildlife in the Everglades and the wider south Florida environment. The chapter begins with an overview of the history of previous ecological risk assessments in south Florida. Next, methods to assess toxicological effects and the difficulties in assessing exposure to fish and wildlife across this varied landscape are reviewed. Risks to south Florida wildlife are then characterized based on multiple lines of evidence for a variety of ecological receptors. The chapter closes with a discussion of potential future risk following the Comprehensive Everglades Restoration Plan.
We analyzed Hg, Cd, Zn, Cu and Fe concentrations in liver samples as well as the Hg concentration and stable isotope ratios of carbon and nitrogen (δ13C and δ15N) in muscle samples from silvertip sharks (Carcharhinus albimarginatus) in Japan. Muscular and hepatic Hg concentrations increased with increased body length. However, these increases were more prominent in the liver than in the muscle samples, and appeared to occur after maturation. Hepatic Zn and Cu concentrations decreased during the growth stage, and then increased concomitantly thereafter with increases in Cd burden. Hepatic Fe concentration from males increased proportionally with increases in body length, whereas no increase was observed in samples from females, probably due to the mother-to-embryo transfer of Fe. The δ13C values tended to decrease with increases in body length, whereas no decrease in the δ15N values was observed.
Sharks are a major component of the top predator guild in oceanic ecosystems, but the trophic relationships of many populations remain poorly understood. We examined chemical tracers of diet and habitat (δ15N and δ13C, respectively) and total mercury (Hg) concentrations in muscle tissue of seven pelagic sharks: blue shark (Prionace glauca), short-fin mako shark (Isurus oxyrinchus), oceanic whitetip shark (Carcharhinus longimanus), scalloped hammerhead shark (Sphyrna lewini), pelagic thresher shark (Alopias pelagicus), crocodile shark (Pseudocarcharias kamoharai) and silky shark (Carcharhinus falciformis), from the data poor south-western tropical Indian Ocean. Minimal interspecific variation in mean δ15N values and a large degree of isotopic niche overlap - driven by high intraspecific variation in δ15N values-was observed among pelagic sharks. Similarly, δ13C values of sharks overlapped considerably for all species with the exception of P. glauca, which had more 13C-depleted values indicating possibly longer residence times in purely pelagic waters. Geographic variation in δ13C, δ15N and Hg were observed for P. glauca and I. oxyrinchus. Mean Hg levels were similar among species with the exception of P. kamoharai which had significantly higher Hg concentrations likely related to mesopelagic feeding. Hg concentrations increased with body size in I. oxyrinchus, P. glauca and C. longimanus. Values of δ15N and δ13C varied with size only in P. glauca, suggesting ontogenetic shifts in diets or habitats. Together, isotopic data indicate that–with few exceptions-variance within species in trophic interactions or foraging habitats is greater than differentiation among pelagic sharks in the south-western Indian Ocean. Therefore, it is possible that this group exhibits some level of trophic redundancy, but further studies of diets and fine-scale habitat use are needed to fully test this hypothesis.
The hypothesis that moderate variability in Sea Surface Temperature (SST) is associated with higher coral cover and slower rates of decline of coral cover within the Florida Keys National Marine Sanctuary (FKNMS) was examined. Synoptic SST time series covering the period 1994–2008 were constructed for the FKNMS with the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer satellite sensors. The SST data were compared with coral-cover time-series data from 36 sites monitored by the Coral Reef and Evaluation Monitoring Program. Sites that experienced moderately high SST variability relative to other sites showed a trend toward higher percentage coral cover in 2008 and relatively slower rates of decline over the 14-year study period. The results suggest that corals at sites that are continuously exposed to moderate variability in temperature are more resilient than corals typically exposed either to low variability or to extremes.
Several recent studies have shown that the use of δ15N analysis to characterize trophic relationships can be useful for tracing biocontaminants in food webs. In this study, concentration of total mercury was measured in tissues from 112 individuals representing 27 species from the arctic marine food web of Lancaster Sound, Northwest Territories. Samples ranged from particulate organic matter through polar bears ( Ursus maritimus). Using δ15N values to identify trophic position, we found that total mercury in muscle tissue biomagnified in this food web. Polar bears were a notable exception, having a lower mean mercury concentration than their main prey, ringed seals ( Phoca hispida). Most vertebrates showed greater variance in mercury concentration than invertebrates, and there was a trend in seabirds toward increased variability in mercury concentration with trophic position. Within species, we found no evidence of bioaccumulation of mercury with age in the muscle tissue of clams (Mya truncata) or ringed seals. Because stable nitrogen isotopes illustrated the relationship in this biome between trophic position and mercury level on a continuous, quantitative scale, we were able to determine that log 10(Hg) (μg/g dry weight) = 0.2(δ15N) - 3.3. The measurement of δ15N values and mercury concentration allowed us to quantitatively assess mercury biomagnification within this extensive arctic marine food web.
The concentration of mercury in fish generally increases with age and size. Although a number of hypotheses have been invoked to explain this pattern, our understanding of the processes regulating the accumulation of mercury in fish is currently inadequate. In this study, we used a simple mass balance model to explore how the relationship between mercury concentration and fish age is affected by bioenergetics processes and prey contamination. We show that mercury concentration increases with fish age when older fish consume more contaminated prey or when metabolic costs associated with activity also increase with fish size. Our analyses further indicate that the relative importance of growth rate, activity costs, and consumption rates for mercury concentration can vary widely. We also show that changes in the energy density of fish and their prey with fish size could also affect the relationship between mercury concentration in fish and age. Application of this mass balance model indicates that bioenergetics models underestimate the activity costs of lake trout. A simple approach is presented to estimate activity costs of fish under field conditions.
Marine food webs are the most important link between the global contaminant, methylmercury (MeHg), and human exposure through consumption of seafood. Warming temperatures may increase human exposure to MeHg, a potent neurotoxin, by increasing MeHg production as well as bioaccumulation and trophic transfer through marine food webs. Studies of the effects of temperature on MeHg bioaccumulation are rare and no study has specifically related temperature to MeHg fate by linking laboratory experiments with natural field manipulations in coastal ecosystems. We performed laboratory and field experiments on MeHg accumulation under varying temperature regimes using the killifish, Fundulus heteroclitus. Temperature treatments were established in salt pools on a coastal salt marsh using a natural temperature gradient where killifish fed on natural food sources. Temperatures were manipulated across a wider range in laboratory experiments with killifish exposed to MeHg enriched food. In both laboratory microcosms and field mesocosms, MeHg concentrations in killifish significantly increased at elevated temperatures. Moreover, in field experiments, other ancillary variables (salinity, MeHg in sediment, etc.) did not relate to MeHg bioaccumulation. Modeling of laboratory experimental results suggested increases in metabolic rate as a driving factor. The elevated temperatures we tested are consistent with predicted trends in climate warming, and indicate that in the absence of confounding factors, warmer sea surface temperatures could result in greater in bioaccumulation of MeHg in fish, and consequently, increased human exposure.
Total mercury (Hg) concentration was determined in the tissues of 10 pelagic fishes in the northern Gulf of Mexico, and dietary tracers (stable isotopes and fatty acids) were used to evaluate the relationship between Hg and feeding history. Highest Hg levels were observed in blue marlin (Makaira nigricans), carcharhinid sharks (Carcha rhinus spp.), and little tunny (Euthynnus alletteratus), ranging from 1.08 to 10.52 ppm. Moderate to low concentrations (< 1.0 ppm) were observed in blackfin tuna (Thunnus atlanticus), cobia (Rachycentron canadum), dolphinfish (Cory phaena hippurus), greater amberjack (Seriola dumerili), king mackerel (Scomberomorus cavalla), wahoo (Acantho cybium solandri), and yellowfin tuna (Thunnus albacares). For the majority of species examined, Hg concentrations did not vary significantly between location (Texas vs. Louisiana) or collection period (2002 and 2003). Significant positive relationships between Hg concentration and body size and (or) weight were detected for 6 of the 10 taxa examined. Hg concentration was also positively associated with trophic position. Three natural associations were identified using stable isotope and fatty acid signatures. Still, no connection between these natural trophic associations and Hg concentration was observed, suggesting that Hg concentration in pelagic fishes was more closely linked to trophic position and size than feeding history.
The elasmobranch fauna of Everglades National Park was studied using longline, gillnet, and rod and reel surveys. Thirteen species of elasmobranchs were identified including three species not previously reported in the park. Species richness was highest in the areas with the greatest influence of marine waters from the Gulf of Mexico and lower in estuarine areas and those subject to periods of hypersalinity. Most elasmobranch species were recorded as juveniles, with at least three species occurring as neonates, and there were few adults of any species. Electivity indices for salinity, temperature, and depth were calculated for Carcharhinus leucas (Valenciennes, 1841), Carcharhinus limbatus (Valenciennes, 1841), Ginglymostoma cirratum (Bonnaterre, 1788), and Negaprion brevirostris (Poey, 1868), and indicated possible habitat partitioning based on these environmental characteristics. Tag-recapture data suggested that N. brevirostris may have a high level of residency and probably remains inside the park for long periods, while all other species showed movements into and out of the park on a regular basis. Results demonstrate the utility of the park for the conservation and management of elasmobranch species and the need to consider how future changes to the environment will affect this important group of predators.
Stable isotope analysis has provided insight into the dietary and habitat patterns of many birds, mammals and teleost fish. A crucial biological parameter to interpret field stable isotope data is tissue incorporation rate, which has not been well studied in large ectotherms. We report the incorporation of carbon and nitrogen into the tissues of leopard sharks (Triakis semifasciata). Because sharks have relatively slow metabolic rates and are difficult to maintain in captivity, no long-term feeding study has been conducted until the point of isotopic steady state with a diet. We kept six leopard sharks in captivity for 1250 days, measured their growth, and serially sampled plasma, red blood cells and muscle for stable carbon and nitrogen isotope analysis. A single-compartment model with first-order kinetics adequately described the incorporation patterns of carbon and nitrogen isotopes for these three tissues. Both carbon and nitrogen were incorporated faster in plasma than in muscle and red blood cells. The rate of incorporation of carbon into muscle was similar to that predicted by an allometric equation relating isotopic incorporation rate to body mass that was developed previously for teleosts. In spite of their large size and unusual physiology, the rates of isotopic incorporation in sharks seem to follow the same patterns found in other aquatic ectotherms.
Predators can impact ecosystems through trophic cascades such that differential patterns in habitat use can lead to spatiotemporal variation in top down forcing on community dynamics. Thus, improved understanding of predator movements is important for evaluating the potential ecosystem effects of their declines.
We satellite-tagged an apex predator (bull sharks, Carcharhinus leucas) and a sympatric mesopredator (Atlantic tarpon, Megalops atlanticus) in southern Florida waters to describe their habitat use, abundance and movement patterns. We asked four questions: (1) How do the seasonal abundance patterns of bull sharks and tarpon compare? (2) How do the movement patterns of bull sharks and tarpon compare, and what proportion of time do their respective primary ranges overlap? (3) Do tarpon movement patterns (e.g., straight versus convoluted paths) and/or their rates of movement (ROM) differ in areas of low versus high bull shark abundance? and (4) Can any general conclusions be reached concerning whether tarpon may mitigate risk of predation by sharks when they are in areas of high bull shark abundance?
Despite similarities in diet, bull sharks and tarpon showed little overlap in habitat use. Bull shark abundance was high year-round, but peaked in winter; while tarpon abundance and fishery catches were highest in late spring. However, presence of the largest sharks (>230 cm) coincided with peak tarpon abundance. When moving over deep open waters (areas of high shark abundance and high food availability) tarpon maintained relatively high ROM in directed lines until reaching shallow structurally-complex areas. At such locations, tarpon exhibited slow tortuous movements over relatively long time periods indicative of foraging. Tarpon periodically concentrated up rivers, where tracked bull sharks were absent. We propose that tarpon trade-off energetic costs of both food assimilation and osmoregulation to reduce predation risk by bull sharks.
Food web relationships in marine systems have traditionally been defined through stomach content analysis, but biochemical techniques have recently emerged to validate and broaden temporal diet patterns. Stable isotope analysis has become a practical tool for evaluating these relationships in aquatic systems; however, routine sampling of muscle tissue captures only part of the trophic information available from each animal. We compared δ 15 N and δ 13 C values among liver, muscle and cartilage in the blue shark Prionace glauca, shortfin mako Isurus oxyrinchus, and common thresher Alopias vulpinus from the northwest Atlantic to show how multiple-tissue sampling captured feeding relationships which would have been invisible to muscle tissue alone. Specifically, we demonstrated evidence of a cephalopod to bluefish Pomatomus saltatrix diet switch in the short- fin mako in spring, and found that the blue shark and common thresher have consistent diets throughout the year. We concluded that consistency observed among stable isotope values in multi- ple tissues implied that the fish were in steady-state with the isotope ratios of their diet and that multiple tissues should be used in trophic assessments of large pelagic fishes. Further experiments to quantify the turnover of stable isotopes in different tissues and species are needed to improve the accuracy of stable-isotope analyses .
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.
Concentrations of total mercury (T-Hg) and methylmercury (MeHg) were measured in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman, an arm of the Arabian Sea between Oman and Iran. Stable isotope ratios (δ13C and δ15N) also were determined to track mercury biomagnification. The average concentration of T-Hg in zooplankton was 21 ± 8.0 ng g−1 with MeHg accounting 10% of T-Hg. Total mercury levels in fish species ranged from 3.0 ng g−1 (Sardinella longiceps) to 760 ng g−1 (Rhizoprionodon acutus) with relatively lower fraction of MeHg (72%) than that found in other studies. The average trophic difference (△13C) between zooplankton and planktivorous fish (Selar crumenopthalmus, Rastrelliger kanagurta, and S. longiceps) was higher (3.4%0) than expected, suggesting that zooplankton may not be the main diet or direct carbon source for these fish species. However, further sampling would be required to compensate for temporal changes in zooplankton and the influence of their lipid content. Trophic position inferred by δ15N and and slopes of the regression equations (log10[T-Hg] = 0.13[δ15N] — 3.57 and log10[MeHg] = 0.14[δ15N] — 3.90) as estimates of biomagnification indicate that biomagnification of T-Hg and MeHg was lower in this tropical ocean compared to what has been observed in arctic and temperate ecosystems and tropical African lakes. The calculated daily intake of methylmercury in the diet of local people through fish consumption was well below the established World Health Organization (WHO) tolerable daily intake threshold for most of the fish species except Euthynnus affinis, Epinephelus epistictus, R. acutus, and Thunnus tonggol, illustrating safe consumption of the commonly consumed fish species.
The use of stable carbon isotopes as a means of studying energy flow is increasing in ecology and paleoecology. However, secondary fractionation and turnover of stable isotopes in animals are poorly understood processes. This study shows that tissues of the gerbil (Meriones unguienlatus) have different δ13C values when equilibrated on corn (C4) or wheat (C3) diets with constant 13C/12C contents. Lipids were depleted 3.0‰ and hair was enriched 1.0‰ relative to the C4 diet. Tissue δ13C values were ranked hair>brain>muscle>liver>fat. After changing the gerbils to a wheat (C3) diet, isotope ratios of the tissues shifted in the direction of the δ13C value of the new diet. The rate at which carbon derived from the corn diet was replaced by carbon derived from the wheat diet was adequately described by a negative exponential decay model for all tissues examined. More metabolically active tissues such as liver and fat had more rapid turnover rates than less metabolically active tissues such as hair. The half-life for carbon ranged from 6.4 days in liver to 47.5 days in hair.
The results of this study have important implications for the use of δ13C values as indicators of animal diet. Both fractionation and turnover of stable carbon isotopes in animal tissues may obscure the relative contributions of isotopically distinct dietary components (such as C3 vs. C4, or marine vs. terrestrial) if an animal's diet varies through time. These complications deserve attention in any study using stable isotope ratios of animal tissue as dietary indicators and might be minimized by analysis of several tissues or products covering a range of turnover times.
Concentrations of mercury (Hg) in fish were compared between two Florida estuaries, the Indian River Lagoon and Florida Bay.
The objective was to determine if differences in Hg concentration exist and to attempt to relate those differences to sources
of Hg. Five hundred and thirteen estuarine fish were collected and analyzed for Hg concentration. Fish species collected were
black drum, bluefish, bonnethead shark, common snook, crevalle jack, gafftopsail catfish, gray snapper, Mayan cichlid, pompano,
red drum, sheepshead, southern flounder, spadefish, and spotted seatrout. Analysis of variance of species-specific Hg data
among the three defined regions of eastern and western Florida Bay and the Indian River Lagoon substantiated regional differences.
Proximity to known anthropogenic sources of Hg appeared to be a significant factor in the distribution of Hg concentration
among the fish collected. Sufficient numbers of crevalle jack, gray snapper, and spotted seatrout were collected to permit
statistical analysis among regions. Hg concentrations in all three of these species from eastern Florida Bay were higher than
those collected in the other two areas. A major fraction of the estuarine fish collected in eastern Florida Bay exceeded one
or more State of Florida or U.S. Food and Drug Administration fish consumption health advisory criteria. In general, fish
from western Florida Bay contained less Hg than those from the Indian River Lagoon, and fish from the Indian River contained
less Hg than those from eastern Florida Bay. Crevalle jack from all areas and spotted seatrout from Florida Bay were placed
on a consumption advisory in Florida. Detailed study of Florida Bay food web dynamics and Hg biogeochemical cycling is recommended
to better understand the processes underlying the elevated Hg levels in fish from eastern Florida Bay. This information may
be vital in the formulation of appropriate strategies in the ongoing South Florida restoration process.
The distribution and salinity preference of immature bull sharks (Carcharhinus leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee
River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating
the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River
and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation
risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important
factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. leucas. The CPUE of <1 year oldC. leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate
in salinities from fresh to fully marine, youngC. leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated.
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.
The stable isotopes of nitrogen (d15N) and carbon (d13C) provide powerful tools for estimating the trophic positions of and carbon flow to consumers in food webs; however, the isotopic signature of a consumer alone is not generally sufficient to infer trophic position or carbon source without an appropriate isotopic baseline. In this paper, I develop and discuss methods for generating an isotopic baseline and evaluate the assump- tions required to estimate the trophic position of consumers using stable isotopes in multiple ecosystem studies. I test the ability of two primary consumers, surface-grazing snails and filter-feeding mussels, to capture the spatial and temporal variation at the base of aquatic food webs. I find that snails reflect the isotopic signature of the base of the littoral food web, mussels reflect the isotopic signature of the pelagic food web, and together they provide a good isotopic baseline for estimating trophic position of secondary or higher trophic level consumers in lake ecosystems. Then, using data from 25 north temperate lakes, I evaluate how d 15N and d13C of the base of aquatic food webs varies both among lakes and between the littoral and pelagic food webs within lakes. Using data from the literature, I show that the mean trophic fractionation of d15N is 3.4‰ (1 SD 5 1‰) and of d13 Ci s 0.4‰ (1 SD 5 1.3‰), and that both, even though variable, are widely applicable. A sen- sitivity analysis reveals that estimates of trophic position are very sensitive to assumptions about the trophic fractionation of d15N, moderately sensitive to different methods for gen- erating an isotopic baseline, and not sensitive to assumptions about the trophic fractionation of d13C when d13C is used to estimate the proportion of nitrogen in a consumer derived from two sources. Finally, I compare my recommendations for generating an isotopic baseline to an alternative model proposed by M. J. Vander Zanden and J. B. Rasmussen. With an appropriate isotopic baseline and an appreciation of the underlying assumptions and model sensitivity, stable isotopes can help answer some of the most difficult questions
In this study, bluefish (Pomatomus saltatrix; age 0-7, n = 632) and their prey (forage fish, macroinvertebrates, zooplankton; n = 2,005) were collected from the Narragansett Bay estuary (RI, USA), and total Hg concentration was measured in white muscle and whole-body tissues, respectively. Bluefish Hg concentrations were analyzed relative to fish length, prey Hg content, and ontogenetic shifts in habitat use and foraging ecology, the latter assessed using stomach content analysis (n = 711) and stable nitrogen (δ(15)N) and carbon (δ(13)C) isotope measurements (n = 360). Diet and δ(13)C analysis showed that age 0 bluefish consumed both benthic and pelagic prey (silversides, sand shrimp, planktonic crustaceans; δ(13)C = - 16.52‰), whereas age 1 + bluefish fed almost exclusively on pelagic forage fish (Atlantic menhaden, herring; δ(13)C = - 17.33‰). Bluefish total Hg concentrations were significantly correlated with length (mean Hg = 0.041 and 0.254 ppm wet wt for age 0 and age 1 + bluefish, respectively). Furthermore, Hg biomagnification rates were maximal during bluefish early life stages and decelerated over time, resulting in relatively high Hg concentrations in age 0 fish. Rapid Hg accumulation in age 0 bluefish is attributed to these individuals occupying a comparable trophic level to age 1 + bluefish (δ(15)N = 15.58 and 16.09‰; trophic level = 3.55 and 3.71 for age 0 and age 1 + bluefish, respectively), as well as juveniles having greater standardized consumption rates of Hg-contaminated prey. Finally, bluefish larger than 30 cm total length consistently had Hg levels above the U.S. Environmental Protection Agency criterion of 0.3 ppm. As such, frequent consumption of bluefish could pose a human health risk, and preferentially consuming smaller bluefish may be an inadequate strategy for minimizing human dietary exposure to Hg.
Concentrations of mercury (Hg) in swordfish (Xiphias gladius) present a food safety problem for many countries. This study analyses total Hg (t-Hg) concentrations in 27 samples of swordfish marketed in Spain in 2005 and in their bioaccessible fractions (soluble concentration in gastrointestinal medium), obtained after applying an in vitro digestion method. Methylmercury (MeHg) was also determined in the bioaccessible fractions. t-Hg concentrations in the samples were 0.41-2.11 mg kg(-1) wet weight, with a mean of 0.96 +/- 0.47 mg kg(-1) wet weight. A total of 37% of the samples exceeded the Hg limit set by Spanish legislation (1.0 mg kg(-1) wet weight). Bioaccessible t-Hg concentrations were 0.17-1.72 mg kg(-1) wet weight (0.63 +/- 0.4 mg kg(-1) wet weight), corresponding to 38-83% (64% +/- 14%) of t-Hg. Bioaccessible MeHg concentrations, representing 94% of the bioaccessible t-Hg concentrations, were 0.16-1.53 mg kg(-1) wet weight, with a mean of 0.49 +/- 0.32 mg kg(-1) wet weight. Children and adults who regularly consume this product in Spain have Hg and MeHg intakes that exceed the tolerable daily intake limits recommended by the Food and Agricultural Organization/World Health Organization (FAO/WHO) and US Environmental Protection Agency (USEPA). These results show the need for recommendations about swordfish consumption by population groups at risk in Spain.
Author Posting. © Cambridge University Press, 2003. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of the Marine Biological Association of the UK 83 (2003): 1347-1350, doi:10.1017/S0025315403008798. Trophic positions (TP) were estimated for the blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and basking shark (Cetorhinus maximus) using stable isotope ratios of carbon ([delta]13C) and nitrogen ([delta]15N). The basking shark had the lowest TP (3·1) and [delta]15N value (10·4‰), whereas the thresher shark had the highest values (4·5, 15·2‰). Mako sharks showed considerable variation in TP and isotopic values, possibly due to foraging from both inshore and offshore waters. Thresher sharks were significantly more enriched in [delta]15N than blue sharks and mako sharks, suggesting a different prey base. The [delta]13C values of thresher sharks and mako sharks varied significantly, but neither was significantly different from that of blue sharks. No statistical differences were found between our TP estimations and those derived from published stomach contents analyses, indicating that stable isotope data may be used to estimate the trophic status of sharks. This work was supported by National Marine Fisheries Service Grant NA16MF1323 to M.E.L.
Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to understand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury accounted for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carbon content in sediments. The concentrations of total mercury in fish muscle were between 0.03 and 2.22 (mean: 0.31) micrograms/g, wet wt, with methyl mercury contributing 83% of total mercury. Methyl mercury concentrations in fish muscle were directly proportional to total mercury concentrations. The relationship of total and methyl mercury concentrations in fish to those of sediments from corresponding locations was fish-species dependent, in addition to several abiotic factors. Among fish species analyzed, hardhead catfish, gafftopsail catfish, and sand seatrout contained the highest concentrations of mercury. Filtered water samples from canals and creeks that discharge into the Florida Bay showed mercury concentrations of 3-7.4 ng/L, with methyl mercury accounting for < 0.03-52% of the total mercury. Consumption of fish containing 0.31 microgram mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to human health.
