An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: part II. Trace element concentrations

Trace element concentrations in common dolphins (Delphinus delphis) in the Celtic Seas ecoregion: Interelement relationships and effects of life history and health status

Given the increased extraction of trace elements for use by new and emerging technologies, monitoring the environmental fate and potential effects of these compounds within the aquatic environment has never been more critical. Here, hepatic trace element concentrations were assessed in a key sentinel predator, the common dolphin (Delphinus delphis), using a long-term dataset. Variation in concentrations were assessed in relation to other elements, time period, decomposition state, sex, age, total body length, sexual maturity and nutritional status, and cause of death. Additionally, mercury toxicity thresholds for evaluating risk were reviewed and employed. Concentrations of elements which bioaccumulate, THg, MeHg, Cd, and Pb, in addition to Se and V, were strongly correlated with age, and/or body length. An association was observed between Zn concentrations and disease status, with significantly higher concentrations measured in individuals that died from infectious disease, compared to other causes. Strong inter-elemental relationships were detected, namely between Hg and Se, MeHg and Se, Cd and Se, and Cu and Zn. While THg:Se molar ratio values were observed to increase with age and body length, approaching equimolarity. THg was largely comprised of inorganic Hg in older individuals, potentially bound to Se, therefore the effects from THg toxicity may possibly be less important than originally assumed. In contrast, higher MeHg:Hg ratio values were reported in juveniles, suggesting a poorer efficiency in demethylation and a higher sensitivity. The generation of data on proportions of hepatic MeHg and inorganic Hg is highly informative to both future toxicity threshold assessments within pollutant indicator assessments, and to understanding the ultimate fate of mercury in the marine web.

Trace Elements in Stenella coeruleoalba: Assessment of Marine Environmental Pollution and Dolphin Health Status

Heavy metals are environmental contaminants and can easily accumulate and biomagnify in various marine species (fishes and mammalians) at the top of the aquatic food chain. Among marine mammalians, the striped dolphin (Stenella coeruleoalba) is the most abundant cetacean in the Mediterranean Sea and is considered to be a sentinel species to monitor the environmental marine pollution. In this study, the contents of toxic metals and metalloids (Cd, Pb, Hg, and As), micro-elements (Ni, Cr, Cu, Fe, Co, Mn, Se and Zn) and macro-elements (Na, Ca, K, Mg and P) were evaluated by ICP-MS analysis in several organs/tissues (lung, skin, muscle and liver) of Stenella coeruleoalba. The assessment of marine environmental pollution and dolphins health status was carried out through further analysis of the same specific parameters such as the metal pollution index (MPI) and coefficient of condition (K). Finally, the correlation between toxic metals and metalloids and essential micro-elements, expressed as molar ratios, was analyzed to evaluate the detoxifying ability (effectiveness) of Zn, Se and Cu. Data obtained showed the presence of toxic metals and metalloids analyzed in the Stenella coeruleoalba samples but the MPI values suggested a low environmental contamination of the Mediterranean Sea where dolphins lived. The content of micro- and macro-elements was found to be in a normal range for this species and predictive of dolphins good health status, as confirmed by the coefficient of condition K. However, the correlation between toxic and essential metals, expressed as molar ratios, showed that the following toxic metals cannot be detoxified by the essential metals: 66Zn/201Hg, 82Se/201Hg, 63Cu/201Hg and 66Zn/52Cr, 82Se/52Cr, 63Cu/52Cr. Therefore, this study highlights the key role of dolphin Stenella coeruleoalba to assess marine pollution and the importance of analyzing the complete mineral profile to evaluate the animal health status.

Trace element bioaccumulation, tissue distribution, and elimination in odontocetes stranded in Florida and Georgia, USA over a 15-year period (2007-2021)

Odontocetes obtain nutrients including essential elements through their diet and are exposed to heavy metal contaminants via ingestion of contaminated prey. We evaluated the prevalence, concentration, and tissue distribution of essential and non-essential trace elements, including heavy metal toxicants, in tissue (blubber, kidney, liver, skeletal muscle, skin) and fecal samples collected from 90 odontocetes, representing nine species, that stranded in Georgia and Florida, USA during 2007-2021. Samples were analyzed for concentrations of seven essential (cobalt, copper, iron, manganese, molybdenum, selenium, zinc) and five non-essential (arsenic, cadmium, lead, mercury, thallium) elemental analytes using inductively-coupled plasma mass spectrometry. Risso's dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus) had the highest median concentrations of mercury, cadmium, and lead, while dwarf sperm whales (Kogia sima) had the lowest. Adult pygmy and dwarf sperm whales that stranded in 2019-2021 had higher concentrations of arsenic, copper, iron, lead, manganese, selenium, thallium, and zinc compared to those that stranded in 2010-2018, suggesting an increasing risk of exposure over time. The highest concentrations of many elements (e.g., cadmium, cobalt, copper, manganese, molybdenum, thallium, zinc) were in fecal samples, illustrating the usefulness of this noninvasively collected sample. Aside from fecal samples, hepatic tissues had the highest concentrations of iron, manganese, mercury, molybdenum, and selenium in most species; renal tissues had the highest concentrations of cadmium; skin had the highest concentrations of zinc; and copper, arsenic, and lead concentrations were primarily distributed among the liver and kidneys. Phylogenetic differences in patterns of trace element concentrations likely reflect species-specific differences in diet, trophic level, and feeding strategies, while heterogeneous distributions of elemental analytes among different organ types reflect differences in elemental biotransformation, elimination, and storage. This study illustrates the importance of monitoring toxic contaminants in stranded odontocetes, which serve as important sentinels of environmental contamination, and whose health may be linked to human health.

Metal and trace element concentrations in cetaceans worldwide: A review

This bibliographical review is a compilation of different scientific publications that reported data on metal concentrations in the muscle tissue of different species of cetaceans from seas and oceans around the world. Forty-nine scientific articles were selected, published over a fifteen-year period (2006-2021) with data on heavy metals and trace elements. The different groups of cetaceans considered in this study generally presented low concentrations of Cd and Pb. The same cannot be said of Hg. The highest concentrations of Hg were found in the groups of false killer whales. Similarly, the use of these groups of cetaceans as bioindicators of metal contamination shows that the Mediterranean Sea is one of the most metallically contaminated areas in the world. This may be due to the closed nature of the Mediterranean Sea and to the fact that it is also a highly populated and industrialized area.

Metal concentrations in feathers of red-legged cormorants (Phalacrocorax gaimardi) and sources of plastic in a nesting colony from northern Chile

Mining industry is increasing the concentrations of heavy metals in coastal ecosystems of northern Chile. The presence of plastic in the nests of red-legged cormorants could be acting as a vector of metal presence in their organism. Here we analyze the source of plastic in the nests of cormorants by characterizing the abundance and type of marine debris in beaches and sea surface and the concentrations of eight metals in their feathers. Plastic was present in overall sampled nests and floating and beach debris are not the main sources of plastic to the nests. Overall analyzed metals were present in the cormorants in the following order: Zn > Cu > Se > Pb > Cd > As > Hg > Cr and Se, Cd and Pb concentrations were above the toxic limit. Further studies should investigate the potential adverse effects that plastics and metals presence may cause in this nesting colony.

Elements in muscle tissue of three dolphin species from the east coast of South Africa

We investigated elemental concentrations in muscle tissue of three species of dolphins incidentally bycaught off the KwaZulu-Natal coastline, South Africa. Thirty-six major, minor and trace elements were analysed in Indian Ocean humpback dolphin Sousa plumbea (n = 36), Indo-Pacific bottlenose dolphin Tursiops aduncus (n = 32) and the Common dolphin Delphinus delphis (n = 8). Significant differences in concentration between the three species were observed for 11 elements (cadmium, iron, manganese, sodium, platinum, antimony, selenium, strontium, uranium, vanadium and zinc). Mercury concentrations (maximum 29 mg/kg dry mass) were generally higher than those reported for coastal dolphin species found elsewhere. Our results reflect a combination of species differences in habitat, feeding ecology, age, and possibly species physiology and exposure to pollution levels. This study confirms the high organic pollutant concentrations documented previously for these species from the same location, and provides a well-founded case for the need to reduce pollutant sources.

Trace Elements and Contaminants Concentrations in Tissues of Caspian Seals (Pusa caspica) along the Iranian Coast

The Caspian seal (Pusa caspica) is an endangered species that only lives in the Caspian Sea. Little information is available on its exposure to contaminants, and no data exists for Southern sub-populations. From 2011 to 2016, tissues samples were collected from 20 Caspian seals to (i) Define the concentration of trace elements in five different matrices and the concentration of 30 pesticides in their blubber; (ii) Determine whether differences in contaminant concentrations are age- or sex-related; (iii) Evaluate if detected concentrations can represent a risk to the species. Age- and sex-related variations were detected for Zn and Hg in the blubber and Fe in the kidney by age only. Exceptionally high Hg concentrations and low levels of hepatic Zn were detected, raising some concern about the reproductive health of seals. Similarly, the DDTs levels detected were in the range of adverse reproductive effects in marine mammals. Based on these results, potentially adverse effects on the immune and endocrine systems of the Caspian seal cannot be ruled out. Therefore, it is of the utmost importance that pollutant monitoring becomes an integral component of conservation strategies for the Caspian seal.

Polluted porpoises: Generational transfer of organic contaminants in harbour porpoises from the southern North Sea

Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and hexachlorobenzene (HCB), bioaccumulate in marine ecosystems. Top predators contain high levels of POPs in their lipid-rich tissues, which may result in adverse effects on their reproductive, immune and endocrine functions. Harbour porpoises (Phocoena phocoena) are among the smallest of cetaceans and live under high metabolic demand, making them particularly vulnerable to environmental pressures. Using samples from individuals of all maturity classes and sexes stranded along the southern North Sea (n = 121), we show the generational transfer of PCBs, PBDEs and HCB from adults to foetuses. Porpoise placentas contained 1.3-8.2 mg/kg lipid weight (lw) Sum-17PCB, <dl-0.08 mg/kg lw Sum-17PBDE and 0.14-0.16 mg/kg lw HCB, which were similar to concentrations in foetus blubber. Contaminant levels increased significantly after birth through suckling. Milk samples contained 0.20-33.8 mg/kg lw Sum-17PCB, 0.002-0.51 mg/kg lw Sum-17PBDE and 0.03-0.21 mg/kg lw HCB. Especially lower halogenated and more toxic contaminants were transferred to calves, exposing them to high levels of contaminants early in life. Of all animals included in this study, 38.5% had PCB concentrations exceeding a threshold level for negative health effects (>9 mg/kg lw). This was particularly true for adult males (92.3% >9 mg/kg lw), while adult females had relatively low PCB levels (10.5% >9 mg/kg lw) due to offloading. Nutritional stress led to higher offloading in the milk, causing a greater potential for toxicity in calves of nutritionally stressed females. No correlation between PCB concentration and parasite infestation was detected, although the probability of a porpoise dying due to infectious disease or debilitation increased with increasing PCB concentrations. Despite current regulations to reduce pollution, these results provide further evidence of potential health effects of POPs on harbour porpoises of the southern North Sea, which may consequently increase their susceptibility to other pressures.

Trace elements in subantarctic false killer whale (Pseudorca crassidens) tissues, including the skin as an offshore bioindicator

On a global scale, cetaceans are recognized well indicators of marine ecosystem health. Trace elements accumulate in their bodies and potentially constitute a toxicological threat. Here, the concentrations of essential Se; unknown physiological elements Br, Rb, Cs, Ni, and Sr; and pollutants arsenic, Cd, Hg, and Ag were assessed in the skin of false killer whales (Pseudorca crassidens) stranded at Estrecho de Magallanes, South America, and next, tissue comparisons and relationships between elemental concentrations in the skin and internal tissues (liver, kidney, spleen, lung, skeletal muscle, and testis) were assessed. Results showed elemental concentration variations among tissues. Selenium concentration was found to be higher in the liver 398 (75) μg g-1 dry weight (DW) (standard deviation in parenthesis), followed by skin. Rubidium and Br concentrations were higher in testis 7.92 (0.42) and 99.1 (5.4) μg g-1 DW, respectively, and Cs in muscle 0.36 (0.12) μg g-1 DW, while Ni concentrations range (<0.05-0.91 μg g-1 DW) did not show differences among tissues. Cadmium and arsenic were found to be higher in kidneys, 71.2 (17.6) and 2.54 (1.77) μg g-1 DW, respectively, while Hg was highest in the liver 1068 (234) μg g-1 DW. Concerning inter-tissue relationships, a positive skin-to-kidney and skin-to-muscle correlations were observed for Cs concentrations, and also Hg showed positive skin-to-spleen, skin-to-kidney, and skin-to-testis correlations, which support its use as potential offshore marine biomonitor.

Persistence, bioaccumulation and vertical transfer of pollutants in long-finned pilot whales stranded in Chilean Patagonia

Long-finned pilot whales (LFPW) are cetaceans with strong social groups often involved in mass strandings worldwide. However, these beachings occur for reasons that are not fully understood. In 2016, 124 LFPW were stranded on the Chilean Patagonian islands, offering a unique opportunity to obtain crucial information on the ecology, biology, and genetics of this population. In addition, we examined whether persistent organic pollutants (POPs) and trace elements (TEs) were responsible for this mass mortality. Stable isotopes (δ¹³C & δ¹⁵N) and genetic analyses were used to reconstruct the trophic ecology, social structure, and kinship of LFPW and compared to POPs and TEs levels found in LFPW. Mitochondrial DNA analyses on 71 individuals identified four maternal lineages within the stranded LFPW. Of these animals, 32 individuals were analyzed for a suite of POPs, TEs, and lipid content in blubber. The highest levels were found for ΣDDXs (6 isomers) (542.46 ± 433.46 ng/g, lw) and for total Hg (2.79 ± 1.91 mg/kg, dw). However, concentrations found in these LFPW were lower than toxicity thresholds and those reported for LFPW stranded in other regions. Evidence was found of ΣDDX, Σ7PCBs, and Cd bioaccumulation and maternal transfer of POPs in mother/offspring groups. Nevertheless, no clear relationship between contaminant concentrations and LFPW mortality was established. Further research is still needed to assess LFPW populations including conservations status and exposure to chemicals in remote areas such as Patagonia.

Two Decades' Variation of Trace Elements in Bones of the Endangered East Asian Finless Porpoise (Neophocaena asaeorientalis sunameri) from the East China Sea, China

There has been increasing concern about trace element accumulation in finless porpoises over the past decades, while the long-term variation of its concentration has been little known. Since most soft tissues of porpoises in the past were not preserved until now, the bone tissue is the only ideal material available. Here, 27 East Asian finless porpoise bone samples collected from Nantong, the East China Sea during two periods (1984-1992 and 2009) were used to explore the temporal variation of nine typical elements' concentration (Fe, Mn, Cu, Ni, Hg, Cr, Pb, As, and Cd, dry weight). An upward trend for total trace element accumulation from 329.04 mg/kg in 1984-1992 to 1535.81 mg/kg in 2009 was found; this could have resulted from the increasing industrial development in the Nantong region. The Mn, Fe, and As levels increased significantly while the concentrations of Cd, Cu, and Pb significantly decreased. Generally, our results suggested that most trace elements posed low threats to East Asian finless porpoises' health during both periods, while elements Mn (2009), Ni (both periods), Fe (2009), and As (2009) posed a potentially higher health risk to porpoises. Thus, the trace element levels warrant concern and continuous monitoring.

Concentration of trace elements in long-finned pilot whales stranded in northern Patagonia, Chile

The use of trace metals and rare-earth elements (REEs) is increasing in the mining, metallurgic, electronic, and automobile industries due to their magnetic, heat-resistant, and phosphorescent properties. While large amounts of these metals are released to the environment, the toxic consequences in marine organisms are poorly understood. In Chile a mass stranding event of long-finned pilot whales (LFPW) (Globicephala melas) occurred in 2016 due to unknown consequences. Al, Ce, Cr, Cu, Tl, and Zn concentrations were analyzed in LFPW blubber tissue and correlated with body size and age class of individuals. While Al and Zn were higher in juvenile individuals, Ce, Cu, Cr, and Tl were higher in adults. This study provides the first base line of trace metals and REE in LFPW from the southern hemisphere and demonstrates the existence and persistence of trace elements in marine top predators from remote ecosystems like the Chilean Patagonia.

Striped dolphins as trace element biomonitoring tools in oceanic waters: Accounting for health-related variables

In Europe, monitoring contaminant concentrations and their effects in the marine environment is required under the Marine Strategy Framework Directive (MSFD, 2008/56/EC). The striped dolphin (Stenella coeruleoalba) is the most abundant small cetacean species in Portuguese oceanic waters, representing a potential biomonitoring tool of contaminant levels in offshore waters. Concentrations of nine trace elements were evaluated by ICP-MS in kidney, liver and muscle samples of 31 striped dolphins stranded in the Portuguese continental coast. The mean renal Cd concentration was high (19.3 μg.g^-1 wet weight, range 0.1-69.3 μg.g^-1 wet weight) comparing to striped dolphins from other locations. Therefore, the present study reports a possibly concerning level of Cd in the oceanic food chain in Portuguese offshore areas. This study also aimed at evaluating potential relationships between trace element concentrations and striped dolphins' biological and health-related variables. Individual length was related with some of the trace element concentrations detected in striped dolphins. Indeed, Cd, Hg and Se bioaccumulated in larger animals, whereas the reverse was observed for Mn and Zn. Striped dolphins with high parasite burdens showed higher levels of Hg, while animals showing gross pathologies presented higher concentrations of Cd and Se. This study reported relationships between trace element concentrations and health-related variables for the first time in striped dolphins and it also provided information on the relative contamination status of Portuguese oceanic waters in comparison to other regions in the world.

Hg and Se in Organs of Three Cetacean Species from the Murcia Coastline (Mediterranean Sea)

We determinated Hg and Se concentrations in liver, kidney, brain, lung and muscle of five bottlenose dolphin (Tursiops truncatus), four common dolphins (Delphinus delphis) and four Risso's dolphin (Grampus griseus) stranded along the Murcia coast, Southeast Spain, in order to evaluate the risk of Hg toxicity. Hg concentrations showed similar concentrations to other individuals in the Mediterranean Sea with the same length in the same period. We observed a positive correlation of Hg and Se in liver (r = 0.948, p < 0.001) and kidney (r = 0.939; p = 0.001) and ratio the Se/Hg molar was higher than 1 in most cases. Our results suggest that the protective effects of Se against Hg toxicity occur in cetaceans. However, we detected levels of Hg described as responsible liver damage and neurotoxicological effects so other tools, as biochemical markers, should be included. Besides, more studies are needed to evaluate the risk of Hg exposure in dolphins from Murcia coastline.

Organic contaminants as an ecological tool to explore niche partitioning: a case study using three pelagic shark species

Chemical contaminant profiles are linked to an animal's niche, providing a potential tool by which to assess resource partitioning in pelagic species. As proof of concept, we examined contaminant signatures in three species of sharks (Isurus oxyrinchus, Prionace glauca, and Alopias vulpinus) known to overlap in both space and time. Since these sharks comprise a predatory guild within the Southern California Bight (SCB), we predicted that species may partition spatial and dietary resources to limit the extent of competitive exclusion. Indeed, species were distinguishable by both total contaminant loads and their contaminant fingerprint, as random forest analysis found that species could be correctly classified 96% of the time. Our results demonstrate the utility of chemical analyses for ecological studies, and how contaminant tracers can be used in combination with traditional methods to elucidate how species may undergo niche partitioning to reduce competition for overlapping resources within predatory guilds.

Trace metals in striped dolphins (Stenella coeruleoalba) stranded along the Murcia coastline, Mediterranean Sea, during the period 2009-2015

Mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se) and arsenic (As) concentrations in internal tissues of 72 striped dolphins (Stenella coeruleoalba) from Murcia Region (Mediterranean coastline) have been investigated for the first time. Hg showed the highest concentration, followed by Se, Cd, As and Pb. In general, the levels of metal found in this study were similar to those described in similar studies in the Mediterranean Sea. However, in some adult specimens, Hg liver concentrations were related with toxic effects in cetacean. A significant correlation was observed with age, likewise between Se and Hg and Cd in tissues, which agree with detoxify effect attributed to Se through inert complex formation. Molar ratio Hg:Se in liver was close to 1:1 in some specimens, which would indicate overload of the Hg-Se detoxify function and compromised health. These results could contribute to a better knowledge of the distribution of these persistent pollutants in the Mediterranean Sea.

Stranded false killer whales, Pseudorca crassidens, in Southern South America reveal potentially dangerous silver concentrations

Silver (Ag) is a non-essential metal known to bioaccumulate in aquatic organisms. We determined Ag concentrations in five false killer whales stranded in South America. Silver concentrations (in dry weight basis) range as 6.62-10.78 μg g^-1 in liver, 0.008-7.41 μg g^-1 in spleen, 0.004-5.71 μg g^-1 in testis, 0.757-1.69 μg g^-1 in kidney, 0.011-0.078 μg g^-1 in lung and < 0.01-0.038 μg g^-1 in muscle, whereas in the single samples of uterus and ovary were 0.051 and 0.023 μg g^-1; respectively. Overall, Ag concentration in liver and kidney exceeded the cetacean toxic thresholds, proposed as "unhealthy concentrations" and "critically dangerous" in liver and kidney. These results warrant further eco-toxicological studies, to examine biological effects of elevated silver levels for individuals and to assess the species' conservation status with respect to marine pollution.

Th2 cytokine bias induced by silver nanoparticles in peripheral blood mononuclear cells of common bottlenose dolphins (Tursiops truncatus)

BACKGROUND

Silver nanoparticles (AgNPs) have been widely used in many commercial products due to their excellent antibacterial ability. The AgNPs are released into the environment, gradually accumulate in the ocean, and may affect animals at high trophic levels, such as cetaceans and humans, via the food chain. Hence, the negative health impacts caused by AgNPs in cetaceans are of concern. Cytokines play a major role in the modulation of immune system and can be classified into two types: Th1 and Th2. Th1/Th2 balance can be evaluated by the ratios of their polarizing cytokines (i.e., interferon [IFN]-γ/Interleukin [IL]-4), and animals with imbalanced Th1/Th2 response may become more susceptible to certain kinds of infection. Therefore, the present study evaluated the in vitro cytokine responses of cetacean peripheral blood mononuclear cells (cPBMCs) to 20 nm citrate-AgNPs (C-AgNP20) by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

METHODS

Blood samples were collected from six captive common bottlenose dolphins (Tursiops truncatus). The cPBMCs were isolated and utilized for evaluating the in vitro cytokine responses. The cytokines evaluated included IL-2, IL-4, IL-10, IL-12, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. The geometric means of two housekeeping genes (HKGs), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and β2-microglobulin (B2M), of each sample were determined and used to normalize the mRNA expression levels of target genes.

RESULTS

The ratio of late apoptotic/necrotic cells of cPBMCs significantly increased with or without concanavalin A (ConA) stimulation after 24 h of 10 µg/ml C-AgNP20 treatment. At 4 h of culture, the mRNA expression level of IL-10 was significantly decreased with 1 µg/ml C-AgNP20 treatment. At 24 h of culture with 1 µg/ml C-AgNP20, the mRNA expression levels of all cytokines were significantly decreased, with the exceptions of IL-4 and IL-10. The IFN-γ/IL-4 ratio was significantly decreased at 24 h of culture with 1 µg/ml C-AgNP20 treatment, and the IL-12/IL-4 ratio was significantly decreased at 4 or 24 h of culture with 0.1 or 1 µg/ml C-AgNP20 treatment, respectively. Furthermore, the mRNA expression level of TNF-α was significantly decreased by 1 µg/ml C-AgNP20 after 24 h of culture.

DISCUSSION

The present study demonstrated that the sublethal dose of C-AgNP20 (≤1 µg/ml) had an inhibitory effect on the cytokine mRNA expression levels of cPBMCs with the evidence of Th2 cytokine bias and significantly decreased the mRNA expression level of TNF-α. Th2 cytokine bias is associated with enhanced immunity against parasites but decreased immunity to intracellular microorganisms. TNF-α is a contributing factor for the inflammatory response against the infection of intracellular pathogens. In summary, our data indicate that C-AgNP20 suppresses the cellular immune response and thereby increases the susceptibility of cetaceans to infection by intracellular microorganisms.

Investigation of silver (Ag) deposition in tissues from stranded cetaceans by autometallography (AMG)

Silver, such as silver nanoparticles (AgNPs), has been widely used in commercial products and may be released into the environment. The interaction between Ag deposition and biological systems is raising serious concerns because of one health consideration. Cetaceans, as the top predators of the oceans, may be exposed to Ag/Ag compounds and suffer negative health impacts from the deposition of these compounds in their bodies. In the present study, we utilized autometallography (AMG) to localize the Ag in the liver and kidney tissues of cetaceans and developed a model called the cetacean histological Ag assay (CHAA) to estimate the Ag concentrations in the liver and kidney tissues of cetaceans. Our results revealed that Ag was mainly located in hepatocytes, Kupffer cells and the epithelial cells of some proximal renal tubules. The tissue pattern of Ag/Ag compounds deposition in cetaceans was different from those in previous studies conducted on laboratory rats. This difference may suggest that cetaceans have a different metabolic profile of Ag, so a presumptive metabolic pathway of Ag in cetaceans is advanced. Furthermore, our results suggest that the Ag contamination in cetaceans living in the North-western Pacific Ocean is more severe than that in cetaceans living in other marine regions of the world. The level of Ag deposition in cetaceans living in the former area may have caused negative impacts on their health condition. Further investigations are warranted to study the systemic Ag distribution, the cause of death/stranding, and the infectious diseases in stranded cetaceans with different Ag concentrations for comprehensively evaluating the negative health effects caused by Ag in cetaceans.

Manganese Concentrations in Tissues and Skin of Three Dolphin Species Stranded in the Croatian Waters of the Adriatic Sea from 1995 to 2013

Manganese concentrations were determined in muscle, kidney, liver, spleen, lung and fat tissues and skin of three cetacean species, the bottlenose (Tursiops truncatus), striped (Stenella coeruleoalba) and Risso's (Grampus griseus) dolphins, stranded along the Croatian Adriatic coast between 1995 and 2013. Mean ranges determined in tissues were (mg/kg, ww): muscle 0.23-0.27, liver 2.87-4.00, kidney 0.66-1.26, spleen 0.37-0.79, lung 0.18-0.57, skin 0.11-0.97, fat 0.06-0.42. The highest Mn mean levels in tissues were measured in species (mg/kg, ww): T. truncates lung 0.41, skin 0.97, fat 0.42; S. coeruleoalba muscle 0.26; G. griseus kidney 1.26, liver 4.00, spleen 0.64. Significant differences of Mn concentrations in the liver (p = 0.034), spleen (p = 0.037) and skin (p = 0.013) were found among the three dolphin species. Significant differences in Mn levels were found between young and adult T. truncates in kidney (p = 0.042), lung (p = 0.0040) and skin (p = 0.0034).

Trace elements in loggerhead turtles (Caretta caretta) stranded in mainland Portugal: Bioaccumulation and tissue distribution

Pollution is among the most significant threats that endanger sea turtles worldwide. Waters off the Portuguese mainland are acknowledged as important feeding grounds for juvenile loggerheads. However, there is no data on trace element concentrations in marine turtles occurring in these waters. We present the first assessment of trace element concentrations in loggerhead turtles (Caretta caretta) occurring off the coast of mainland Portugal. Also, we compare our results with those from other areas and discuss parameters that may affect element concentrations. Trace element concentrations (As, Cd, Cu, Pb, Mn, Hg, Ni, Se, Zn) were determined in kidney, liver and muscle samples from 38 loggerheads stranded between 2011 and 2013. As was the only element with higher concentrations in muscle (14.78 μg g^-1 ww) than in liver or kidney. Considering non-essential elements, Cd presented the highest concentrations in kidney (34.67 μg g^-1) and liver (5.03 μg g^-1). Only a weak positive link was found between renal Cd and turtle size. Inter-elemental correlations were observed in both liver and kidney tissues. Hepatic Hg values (0.30 ± 0.03 μg g^-1) were higher than values reported in loggerheads in the Canary Islands but lower than in Mediterranean loggerheads. Cd concentrations in the present study were only exceeded by values found in turtles from the Pacific. Although many endogenous and exogenous parameters related with complex life cycle changes and wide geographic range may influence trace element accumulation, the concentrations of Cd are probably related to the importance of crustaceans in loggerhead diet in the Portuguese coast.

Assessing trace elements in striped dolphins from the Strait of Gibraltar: Clues to link the bioaccumulation in the westernmost Mediterranean Sea area and nearest Atlantic Ocean

Dolphins are considered sentinel species in the marine environment. The Strait of Gibraltar is the only passage between the Mediterranean Sea and the Atlantic Ocean, being the transitional region which connects these two basins and one of the most important routes of cetacean migration worldwide. In this work, eight trace elements (TE) were studied in 45 samples of liver, kidney and muscle, from 15 specimens stranded in this study area. The preliminary results show, among others, the patterns of distribution of the TE in the target organs studied, the influence of sex, length and developmental stage in these TE concentrations and the Se/Hg ratio. Subsequently, the results of TE concentrations in liver have being compared to previous data on S. coeruleoalba from the westernmost Mediterranean Sea and the nearest Atlantic Ocean. For some elements (e.g. for As), concentrations are similar to those obtained from Atlantic samples, despite in other cases (e.g. for Cd) results are lined up with those observed in Mediterranean studies. In addition, in the case of some TE (e.g. Se and Zn) the results are in the middle of those reported for both basins, reinforcing the idea of the Strait of Gibraltar being a transitional zone. Present study is the first research regarding this issue in this outstanding region, aiming to give insights of how this matchless area can help to link TE concentrations observed in these Atlantic and Mediterranean threatened species.

Spatiotemporal Trends of Heavy Metals in Indo-Pacific Humpback Dolphins (Sousa chinensis) from the Western Pearl River Estuary, China

We assessed the spatiotemporal trends of the concentrations of 11 heavy metals (HMs) in the liver and kidney of Indo-Pacific humpback dolphins (Sousa chinensis) from western Pearl River Estuary (PRE) during 2004-2015. The hepatic levels of Cr, As, and Cu in these dolphins were among the highest reported for cetaceans globally, and the levels of Zn, Cu, and Hg were sufficiently high to cause toxicological effects in some of the animals. Between same age-sex groups, dolphins from Lingdingyang were significantly more contaminated with Hg, Se, and V than those from the West-four region, while the opposite was true for Cd. Generalized additive mixed models showed that most metals had significant but dissimilar temporal trends over a 10-year period. The concentrations of Cu and Zn increased significantly in recent years, corresponding to the high input of these metals in the region. Body-length-adjusted Cd levels peaked in 2012, accompanied by the highest annual number of dolphin stranding events. In contrast to the significant decrease in HM levels in the dolphins in Hong Kong waters (the eastern reaches of the PRE), the elevated metal exposure in the western PRE raises serious concerns.

Trace element concentrations in the Mediterranean monk seal (Monachus monachus) in the eastern Mediterranean Sea

The Mediterranean monk seal (Monachus monachus) is one of the most endangered marine mammals in the world. The biggest sub-population of the species survives in Greece, where understanding the effects of pollution on the survival of the species has been identified as a national research and conservation priority. From 1990 to 2013 we collected tissue samples from 59 deceased monk seals in order to: (i) Define the concentration of trace elements (As, Pb, Cd, Hg, Se, Cr, Ni) in three different matrices (i.e., blubber, liver and kidney), (ii) Determine whether differences in trace element concentrations are age- or gender-related, (iii) Evaluate the potential effects of these pollutants. The study recorded differences in trace element concentrations among matrices, but in general, trace element exposure in Mediterranean monk seals in Greece was low and within the non-acutely toxic levels for Pinnipeds. Only arsenic concentrations were at the upper limit of the normal range observed in other marine mammals (0.69±0.55mg/kg w.w. in blubber, 0.79±0.62mg/kg w.w. in liver and 0.79±0.59mg/kg w.w. in kidney). We recorded also exceptionally high Hg concentrations in a single adult female (24.88mg/kg w.w.). Age- and gender-related differences were also recorded and were due to various biological, ecological and chemical factors. Based on the results of the study, potentially adverse effects on the immune and endocrine system of the Mediterranean monk seal from some pollutants (e.g., As, Cd, Se, Ni, Cr) cannot be ruled out, which may expose the Mediterranean seal population in Greece to epizootics and stochastic phenomena of mass mortality. It is therefore of utmost importance that pollutant monitoring becomes an integral component of the standard monitoring protocol of the endangered Mediterranean monk seal in the eastern Mediterranean.

Bioaccumulation of trace element concentrations in common dolphins (Delphinus delphis) from Portugal

The common dolphin (Delphinus delphis) is one of the most abundant species in Atlantic Iberia, representing a potentially important tool to assess the bioaccumulation of trace elements in the Iberian marine ecosystem. Nine elements (As, Cd, Cu, Hg, Mn, Ni, Pb, Se and Zn) were evaluated in 36 dolphins stranded in continental Portugal. Dolphins had increasing Hg concentrations (16.72μg·g^-1 ww, liver) compared with previous studies in Atlantic Iberia, whereas Cd concentrations (2.26μg·g^-1 ww, kidney) fell within reported ranges. The concentrations of some trace elements (including Cd and Hg) presented positive relationships with dolphin length, presence of parasites and gross pathologies. Common dolphins may help biomonitoring more offshore Atlantic Iberian areas in future studies, which would otherwise be difficult to assess.

Trace elements in striped dolphins (Stenella coeruleoalba) from the Eastern Mediterranean: A 10-years perspective

Concentrations of Hg, Se, Cd, Cu, Zn, Fe, Mn and As, in kidney, liver, muscle and blubber from 7 specimens of Stenella coeruleoalba, stranded along the Israeli Mediterranean coast (IMC) from 2006 to 2011 (2011-series) were determined and compared to previous data on S. coeruleoalba from the IMC (2001-series). No differences were observed in essential and toxic elements concentrations, between the two series, except for hepatic Mn which was higher in the latter. Hg/Se molar ratios in blubber, kidney and liver increased linearly with log Hg concentrations, while muscle was more heterogenic in this respect. Means (±SD) of hepatic Hg concentrations (134±89 and 181±200mgkg(-1), from the 2011 and 2001 series, respectively) were similar to that found in 2007-2009 specimens from Spain, possibly reflecting the relatively high natural background levels of mercury in the Mediterranean Sea.

Biological variables and health status affecting inorganic element concentrations in harbour porpoises (Phocoena phocoena) from Portugal (western Iberian Peninsula)

The coastal preferences of harbour porpoise (Phocoena phocoena) intensify their exposure to human activities. The harbour porpoise Iberian population is presently very small and information about the threats it endures is vital for the conservation efforts that are being implemented to avoid local extinction. The present study explored the possible relation between the accumulation of trace elements by porpoises and their sex, body length, nutritional state, presence of parasites and gross pathologies. The concentrations of arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn) and selenium (Se) were evaluated in 42 porpoises stranded in Portugal between 2005 and 2013. Considering European waters, porpoises stranded in Portugal present the highest Hg concentrations and the lowest Cd concentrations, which may reflect dietary preferences and the geographic availability of these pollutants. While no effect of sex on trace element concentrations was detected, there was a positive relationship between porpoise body length and the concentration of Cd, Hg and Pb. Animals in worse nutritional condition showed higher levels of Zn. Harbour porpoises with high parasite burdens showed lower levels of Zn and As in all analysed tissues and also lower levels of renal Ni, while those showing gross pathologies presented higher Zn and Hg levels. This is the first data on the relationship between trace elements and health-related variables in porpoises from southern European Atlantic waters, providing valuable baseline information about the contamination status of this vulnerable population.

Ecological variables influencing trace element concentrations in bottlenose dolphins (Tursiops truncatus, Montagu 1821) stranded in continental Portugal

Both the conservation status of bottlenose dolphins (Tursiops truncatus) (Habitats Directive 92/43/CEE, Annex II) and the Marine Strategy Framework Directive demand for data on their ecology and anthropogenic threats. To evaluate the bottlenose dolphin's toxicological status in continental Portugal, several trace elements (As, Cd, Cu, Hg, Mn, Ni, Pb, Se, Zn) were determined in 25 stranded individuals. The potential effect of sex, body length and stranding location on trace element concentrations was analysed. In the present study, bottlenose dolphins presented high mercury levels, only exceeded by animals from the Mediterranean and Adriatic seas. Only essential elements were influenced by dolphin sex, whereas Cd, Hg and Pb bioaccumulated in larger dolphins, and hepatic Hg and Cd concentrations were higher in the northwest coast of continental Portugal. The location effect may relate to variations in bottlenose diet and trace element availability, according to the proximity to anthropogenic sources in the Atlantic Iberian coast.

Mercury and selenium status of bottlenose dolphins (Tursiops truncatus): A study in stranded animals on the Canary Islands

The mercury (Hg) level in the marine environment has tripled in recent decades, becoming a great concern because of its high toxic potential. This study reports Hg and selenium (Se) status, and the first Se/Hg molar ratio assessment in bottlenose dolphins (Tursiops truncatus) inhabiting the waters of the Canary Islands. Total Hg and Se concentrations were determined in the blubber and liver collected from 30 specimens stranded along the coasts of the archipelago from 1997 to 2013. The median values for total Hg in the blubber and liver were 80.83 and 223.77 μg g(-1) dry weight (dw), and the median levels for Se in both tissues were 7.29 and 68.63 μg g(-1) dw, respectively. Hg concentrations in the liver were lower than 100 μg g(-1) wet weight (ww), comparable to those obtained in bottlenose dolphins from the North Sea, the Western Atlantic Ocean and several locations in the Pacific Ocean. The Mediterranean Sea and South of Australia are the most contaminated areas for both elements in this cetacean species. In addition, it must be stressed that the levels of Hg and Se in the liver showed an increasing trend with the age of the animals. As expected, a strong positive correlation between Hg and Se was observed (rs=0.960). Surprisingly, both younger and older specimens had a Se/Hg molar ratio different from 1, suggesting that these individuals may be at greater toxicological risk for high concentrations of both elements or a deficiency of Se without a protective action against Hg toxicity.

An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: part I. Persistent organic pollutants

Concentrations and patterns of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the blubber of the five most common toothed whales off the Northwest Iberian Peninsula (NWIP), specifically common dolphin, long-finned pilot whale, harbour porpoise, striped dolphin and bottlenose dolphin, were investigated. The study revealed that differences in PCB and PBDE concentrations among the species are highly dependent on age and sex but also on ecological factors such as trophic level, prey type and habitat. Of the five species studied, bottlenose dolphin and harbour porpoise showed the greatest concentrations of PCBs. Both species exceed the toxic threshold of 17μgg(-1) lipid weight (PCB Aroclor equivalent) for health effects on marine mammals, for 100% and 75% of the individuals tested, respectively. Overall, the PCB and PBDE levels observed in the NWIP toothed whales were of the same order of magnitude or lower than those reported by previous studies in areas of the NE Atlantic. However, they are often higher than those for toothed whales from the southern Atlantic and Pacific Ocean.