Cephalopods as a vector for the transfer of cadmium to top marine predators in the north-east Atlantic Ocean

Levels of trace elements in the blood of chick gulls from the English Channel: Spatial and trophic implications

Anthropogenic activity has disturbed the natural distribution and circulation of trace elements in the environment. This has led to increased background levels of numerous elements, causing global pollution. In this context, seabirds are relevant bioindicators of environmental contamination. This study focuses on the ecological factors that influence the concentrations of 14 trace elements in the blood of the chicks of three sympatric gull species from the French coast of the English Channel. Between 2015 and 2017, 174 birds were sampled in the industrialised Seine Estuary (in the city of Le Havre and on Ratier Island) and in the remote Chausey Islands, 200 km to the west. We also considered the Se:Hg molar ratio using Hg concentrations in those birds. Ag and V concentrations were below the quantification limit in all cases, while the fraction of non-quantified samples was higher than 30 % for Cd, Cr and Ni. Among the elements quantified in the samples, the lowest concentrations were noted for Co and the highest for Fe, building the following order: Co < Cd < Ni < Mn ≤ Pb < Cr < Hg < Cu < Se < As < Zn < Fe. No unanimous scheme of concentrations among elements, species and sites existed. Similarly, different models were fitted and different factors were significant for different species and elements. We observed the biomagnification of As and the biodilution of Pb. Pb concentrations were also highest in the industrial site in the city of Le Havre. Despite the high proportion of non-quantified samples for Cd, Cr and Ni, we continued to notice higher concentrations in the marine environment of the Chausey Islands. Concentrations of some elements clearly revealed habitat dependence. In some cases the Se:Hg molar ratio was lower than 4, a threshold for diminishing Hg toxicity by Se.

Assessing the impacts of trace element contamination on the physiology and health of seabirds breeding along the western and southern coasts of Portugal

Coastal seabirds serve as sentinels of ecosystem health due to their vulnerability to contamination from human activities. However, our understanding on how contaminant burdens affect the physiological and health condition of seabirds is still scarce, raising the uncertainty on the species' vulnerability vs tolerance to environmental contamination. Here, we quantified 15 Trace Elements (TE) in the blood of gull (yellow-legged gull Larus michahellis and Audouin's gull Ichthyaetus audouinii) and shearwater (Cory's shearwater Calonectris borealis) adults, breeding in five colonies along the Portuguese coastline. Additionally, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were quantified to elucidate foraging habitat and trophic ecology of adults, to identify potential patterns of TE contamination among colonies. We used immuno-haematological parameters as response variables to assess the influence of TE concentrations, stable isotope values, and breeding colony on adults' physiological and health condition. Remarkably, we found blood mercury (Hg) and lead (Pb) concentrations to exceed reported toxicity thresholds in 25% and 13% of individuals, respectively, raising ecotoxicological concerns for these populations. The breeding colony was the primary factor explaining variation in five out of six models, underlining the influence of inherent species needs on immuno-haematological parameters. Model selection indicated a negative relationship between erythrocyte sedimentation rate and both Hg and selenium (Se) concentrations, but a positive relationship with δ13C. The number of immature erythrocyte counts was positively related to Hg and Se, particularly in yellow-legged gulls from one colony, highlighting the colony-site context's influence on haematological parameters. Further research is needed to determine whether essential TE concentrations, particularly copper (Cu) and Se, are falling outside the normal range for seabirds or meet species-specific requirements. Continuous monitoring of non-essential TE concentrations like aluminium (Al), Hg, and Pb, is crucial due to their potential hazardous concentrations, as observed in our study colonies.

Bioaccumulation of trace elements in marine mammals: New data and transplacental transfer on threatened species

Coastal areas are affected by urban, industrial and agriculture pollutants runoff, wastewater and stormwater discharges, making this environment the final repository of chemical contaminants. These contaminants have the potential to spread out to the entire food chain, impacting marine life and the quality of their habitat. In this aspect, the concept of marine mammals as bioindicators provides an approach to the degree of contamination in the environment and to the identification and management of multiple sources of contaminants. The present study analyzed several elements like As, Ba, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, V and Zn in liver tissue from two dolphin species: Sotalia guianensis, a near-threatened species, and the vulnerable Pontoporia blainvillei. In the study, we also investigated if dolphins (population) recorded using the heaviest urban areas have higher concentrations of contaminants in their tissues. Dolphin samples (n = 40 S. guianensis; n = 97 P. blainvillei) were collected by daily monitoring carried out by Santos Basin Beach Monitoring Project (PMP-BS), from stranded individuals found in São Paulo state. The Spearman's rank correlation showed distinct correlations in the accumulation of trace elements by both species, indicating different sources of exposure to the elements studied or distinct biochemical processes between species. Interspecific and intraspecific variations were observed, possibly related to the individual distribution and feeding habits. Correlations were observed between age and concentrations of trace elements, positive for Cd, Hg and Mo. Finally, our findings indicate high levels of Cu, Zn, and concentrations of As, V and Hg in fetuses, in particular, an analysis was performed on a fetus found inside a stranded individual, indicating placental transfer as the first route of exposure for some elements.

Heavy metal and trace element concentrations in the blood of scalloped hammerhead sharks (Sphyrna lewini) from La Paz Bay, México

Sharks are particularly susceptible to bioaccumulation due to their life history characteristics and trophic position within marine ecosystems. Despite this, studies of bioaccumulation cover only a small proportion of extant species. In this study we report concentrations of trace elements and heavy metals in blood samples of Sphyrna lewini for the first time. We report high concentrations of several trace elements and heavy metals, with concentrations of some elements exceeding the limit determined safe for human consumption. High elemental concentrations may reflect biochemical differences between blood plasma and other tissues; however, they may also be symptomatic of high levels of exposure triggered by anthropogenic activities. We also provide evidence of elemental accumulation through ontogeny, the nature of which differs from that previously reported. Ultimately, this baseline study increases our understanding of interspecific and intraspecific variation in bioaccumulation and ecotoxicology in elasmobranchs which may prove important in ensuring adequate management.

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.

Comparison of Cd, Cu, Se, and Zn Concentration in the Muscle and Hepatopancreas of Sepia pharaonis and Uroteuthis duvauceli in the North of Persian Gulf (Iran)

The objective of this research was to examine and contrast the levels of cadmium (Cd), copper (Cu), zinc (Zn), and selenium (Se) in the muscle and hepatopancreas tissues of two species, namely pharaoh cuttlefish (Sepia pharaonis) and Indian squid (Uroteuthis duvauceli), from the Persian Gulf. A total of thirty individuals of each species were gathered in January 2009 from the northern waters of the Persian Gulf. The metal concentrations were significantly higher in muscle tissue (p < 0.05) than in other tissues. S. pharaonis had higher metal concentrations than U. duvauceli. In the muscle and hepatopancreas samples of S. pharaonis, the highest mean concentrations were found to be for Zn (58.45 ± 0.96 µg/g dw) and Cu (1541.47 ± 192.15 µg/g dw), respectively. In U. duvauceli, the highest concentration of measured elements was seen for Zn in both muscle (36.52 ± 0.56 µg/g dw) and hepatopancreas (60.94 ± 2.65 µg/g dw). Se had the lowest concentration among the elements measured in both species. There was a negative and significant correlation between Cu and biometrical factors (total body length and weight) in both muscle and hepatopancreas samples of S. pharaonic and only in the muscle samples of U. duvauceli (p < 0.01, R2 =  - 052; p < 0.01, R2 =  - 0.055). However, there was a strong correlation between Zn and biometrical factors in hepatopancreas samples of both species. The comparison of metal concentrations with standards revealed that only Cd levels in S. pharaonis exceeded the ESFA and WHO standards, whereas other metals were below the standards.

Heavy metal concentrations in sharks, rays and chimaeras from the western Mediterranean Sea

The potential bioaccumulation of pollutants, such as heavy metals, may pose a threat to the western Mediterranean chondrichthyans and human consumers. Therefore, the first extensive assessment of cadmium (Cd), lead (Pb), and copper (Cu) concentrations in the muscle tissue of 17 species of sharks, rays, and chimaeras in this region was conducted via Microwave Assisted Extraction (MAE) and Graphite Furnace Atomic Absorption Spectrometry (GFAAS). Significant differences between species were observed, particularly related to the rabbit fish (Chimaera monstrosa) and the velvet belly lantern shark (Etmopterus spinax), which exceeded the European Union (EU) Commission Regulation 2023/915 threshold of Cd. Overall, heavy metal concentrations correlated negatively with size and trophic level but positively with depth. Although the consumption of these species may entail minimal risk to adult humans, caution is advised, especially for children. These findings are important due to the widespread consumption of chondrichthyans in many western Mediterranean regions.

What do small cetaceans tell us about trace elements pollution on the Argentinean coast? Franciscana dolphin as a biomonitor

Trace elements (TEs) constitute the oldest emerging pollutants globally, most occur from natural sources, but a few are derived from anthropogenic sources. Marine mammals are considered bioindicators of ecosystem contamination. The aims of this review is compile reports on essential and nonessential TEs occurrence in small cetaceans from Argentinean waters; and to review the existing information on the concentration of TEs in the Franciscana dolphin, a biomonitor species of the Argentine coastal marine ecosystem. We searched reports where levels of TEs were present in small cetaceans from and eight species were analysed: Pontoporia blainvillei, Tursiops truncatus gephyreus, Kogia breviceps, Delphinus delphis, Lagenorhynchus obscurus, Lagenodelphis hasei, Cephaloryhchus commersonii and Ziphius cavirostris. Essential TEs like Zn, Cu, Mn, Cr, Fe, Co, Ni, Mo, Se, As, Au, Ag, Sn, and nonessential TE as Pb, Cd, Hg, As was considered. The reports compiled in this article analysed kidney, liver, muscle and occasionally brain, skin, lung and spleen, covering a temporal range of 30 years, from 1982 to 2016. Of data analysis, we identify knowledge gaps, species of small cetaceans for which the concentration of trace metals is not yet known and areas on the Argentine coast where there are no reports that analyse them. The most recent information corresponds to the 2010 decade, and in those subsequent publications, the samples were taken at that time. This emphasizes the importance of reviewing this data, in order to compare old and new datasets, create contamination timelines and evaluate possible increases or decreases of contaminants in different study areas. The information recopilated will serve as valuable baselines to detect the future impact of increasing human, even natural, activities on marine ecosystems in the South Atlantic Ocean.

Toxic metals in Loggerhead sea turtles (Caretta caretta) stranded freshly dead along Sicilian coasts

BACKGROUND

The Loggerhead sea turtle (Caretta caretta) is a marine reptile belonging to a monophyletic group of chelonians. As these animals are long-lived, they have the ability to accumulate pollutants.

AIM

To collect epidemiological data on toxic metals in marine Loggerhead sea turtles.

MATERIALS AND METHODS

Forty Loggerhead sea turtles comprising 25 males and 15 females stranded freshly dead between 2013 and 2018 along the coasts of Sicily, Southern Italy, were examined for arsenic, cadmium, and lead accumulation in muscle and adipose tissues by means of a validated ICP-MS method. A modified K index as a growth condition factor, namely Fulton's K index, was used. Samples were tested in duplicate. A Wilcoxon rank sum test was carried out to evaluate metal contents differences between muscle and adipose tissues and between genders.

RESULTS

The Fulton's K index suggested a good body condition of the C. caretta recovered with mean values of 5.34 ± 3.40 (n = 40; ±SD). Detectable concentrations of lead were found in 70% of the samples analysed with mean values of 0.65 ± 1.67 mg/kg wet weight and 0.51 ± 1.29 mg/kg wet weight in muscle and adipose tissues, respectively. No significant differences in arsenic, cadmium, and lead were detected between genders. In addition, no significant correlation was found between modified K index and concentrations of arsenic, cadmium, and lead.

CLINICAL RELEVANCE

Findings on muscle and adipose tissues suggest chronic exposure of Caretta caretta to high concentrations of especially lead which might negatively affect health and welfare of these marine turtles although body condition was good.

Variation of 210-polonium in the cephalopod community from the Bay of Biscay, North-East Atlantic

Among natural radionuclides, 210Po is the major contributor to the radiation dose received by marine organisms. In cephalopods, 210Po is concentrated in the digestive gland, which contains over 90% of the whole-body burden of the nuclide. Although previous studies showed that 210Po was taken up independently of 210Pb, its parent nuclide, very little is known about the factors influencing its levels in cephalopods. To the best of our knowledge, no studies investigated 210Po levels in different species at the same time. In the present study, 210Po was analysed in the digestive gland of 62 individuals from 11 species representing a large range of feeding ecologies and habitats, including squids, cuttlefish and octopus species from coastal to deep-oceanic habitats. Among species, the highest activity was measured in Loligo vulgaris (5720 ± 3606 Bq/kg) and the lowest in T. megalops (188 Bq/kg). However, considering the habitats (benthic vs pelagic and neritic vs oceanic), no significant differences appeared. At the species level, no differences between sexes were found so both sexes were plotted together to test the size effect for species with at least 8 individuals (i.e., Eledone cirrhosa, L. vulgaris, L. forbesi and Sepia officinalis). In the first three species, 210Po levels decreased significantly with increasing size or weight but not in S. officinalis. In squid, this could be related to ontogenetic changes in diet from a high proportion of crustaceans (high Po content) in small individuals to fish (low Po content) in larger individuals, while the high dietary plasticity of S. officinalis at all stages of its life cycle could explain the lack of decrease in 210Po with size. In comparison to the few data from the literature, the levels of 210Po concentrations in the cephalopod community of the Bay of Biscay were overall in the same range than those reported in other cephalopods, varying across 4 orders of magnitude. Further studies are needed to understand the mechanism of retention in the cephalopod digestive gland.

Multidimensional trace metals and nutritional niche differ between sexually immature and mature common dolphins (Delphinus delphis)

There is a need to understand the links between metals and nutrition for apex marine predators, which may be subject to different ecotoxicological effects at different life stages. We combined stomach content analyses (SCA), prey composition analysis (PCA), the Multidimensional Niche Framework (MNNF) with Bayesian multivariate ellipses, trace metal analysis and nicheROVER to investigate nutrition and trace metals across sex, age, and sexual maturity status in common dolphins (Delphinus delphis) from New Zealand. A broader prey composition niche breadth (SEAc) was estimated for immature compared to mature conspecifics, showing a higher degree of prey and nutrient generalism driven by protein (P) intake. Cd and Zn niche similarities suggests these metals were incorporated through similar prey in both immature and mature dolphins, whereas Hg and Se niche divergence indicates uptake occurred via different prey. Our multidisciplinary assessment demonstrated how nutrients and metal interactions differ in common dolphins depending upon sexual maturity. This approach has relevance when considering how marine pollution, environmental fluctuations and climate change may affect nutritional and trace metal interactions during different reproductive stages within marine predators.

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.

Heavy metal contamination in pristine environments: lessons from the Juan Fernandez fur seal (Arctocephalus philippii philippii)

Heavy metals, including mercury (Hg) and cadmium (Cd), occur naturally or anthropogenically and are considered toxic to the environment and human health. However, studies on heavy metal contamination focus on locations close to industrialized settlements, while isolated environments with little human activity are often ignored due to perceived low risk. This study reports heavy metal exposure in Juan Fernandez fur seals (JFFS), a marine mammal endemic to an isolated and relatively pristine archipelago off the coast of Chile. We found exceptionally high concentrations of Cd and Hg in JFFS faeces. Indeed, they are among the highest reported for any mammalian species. Following analysis of their prey, we concluded that diet is the most likely source of Cd contamination in JFFS. Furthermore, Cd appears to be absorbed and incorporated into JFFS bones. However, it was not associated with mineral changes observed in other species, suggesting Cd tolerance/adaptations in JFFS bones. The high levels of silicon found in JFFS bones may counteract the effects of Cd. These findings are relevant to biomedical research, food security and the treatment of heavy metal contamination. It also contributes to understanding the ecological role of JFFS and highlights the need for surveillance of apparently pristine environments.

Trends in hepatic cadmium concentrations in marine bird species from the Canadian Arctic

Cadmium (Cd) is a trace element of toxicological concern that has been monitored in marine birds inhabiting the Canadian Arctic since 1975. Despite nearly 50 years of monitoring, research to date has largely evaluated single species, locations, or time points, and there is as of yet no holistic overview that jointly considers all available Cd data. We addressed this information gap by combining and analyzing most of the existing data on hepatic Cd concentrations in marine birds from the Canadian Arctic. Using data collected between 1975 and 2018 from eight seabird species from 12 Arctic breeding colonies, we examined temporal, spatial, and interspecific variation in hepatic Cd levels, and we evaluated possible drivers of marine bird Cd loads. Hepatic Cd concentrations ranged from 1.6 to 124 μg/g dry weight across species, and were highest in thick-billed murres (Uria lomvia) and king eiders (Somateria spectabilis), and lowest in black guillemots (Cepphus grylle), black-legged kittiwakes (Rissa tridactyla), and long-tailed ducks (Clangula hyemalis). All sites with multiple years of data showed interannual fluctuations in Cd, which were correlated with the North Atlantic Oscillation (NAO) index and with the previous year's June sea ice coverage, where marine birds exhibited higher Cd concentrations in positive NAO years and following years with lower sea ice coverage. Climate change is likely to shift the NAO to being more negative and to reduce sea ice coverage, and our results thus identify various ways by which climate change could alter Cd concentrations in marine birds in the Canadian Arctic. Understanding variations in marine bird contaminant burdens, and how these may be alters by other stressors such as climate change, is important for long-term marine bird conservation efforts.

Bioaccumulation of heavy metals in estuaries in the southwest Atlantic Ocean

The southwestern Atlantic Ocean is home to highly productive regions, composed of a mosaic of both protected and anthropogenically impacted areas, including the estuaries of Paranaguá, Cananéia, and Santos. In this study, concentrations of metals were measured in sediments and in marine organisms, collected from these three Brazilian estuaries. The higher concentrations of metals in the sediments from the Santos estuary are due to having the greatest intensity of anthropogenic activities. There is bioaccumulation of As, Cu, Ni, and Pb in benthic invertebrates, As in fish, and Se and Zn in all studied trophic groups. Comparing the biota among estuaries, levels were highest for Cr, Cu, Pb, Se, and Zn in Paranaguá, As in Cananéia, and Ni in Santos; results justified due to anthropogenic activities, natural sources, and geochemical and hydrodynamics characteristics of each region that affect the bioavailability of metals. The results showed that these regions of the Atlantic present higher levels of metals in the biota than several coastal regions worldwide, and signal that food security may be compromised. Highlighting the need for better impact assessment, monitoring, and managing is deemed necessary as these regions are globally recognized as hotspots of biodiversity and are considered priority areas for conservation.

Cuttlefish color change as an emerging proxy for ecotoxicology

Lately, behavioral ecotoxicology has flourished because of increasing standardization of analyses of endpoints like movement. However, research tends to focus on a few model species, which limits possibilities of extrapolating and predicting toxicological effects and adverse outcomes at the population and ecosystem level. In this regard, it is recommended to assess critical species-specific behavioral responses in taxa playing key roles in trophic food webs, such as cephalopods. These latter, known as masters of camouflage, display rapid physiological color changes to conceal themselves and adapt to their surrounding environments. The efficiency of this process depends on visual abilities and acuity, information processing, and control of chromatophores dynamics through nervous and hormonal regulation with which many contaminants can interfere. Therefore, the quantitative measurement of color change in cephalopod species could be developed as a powerful endpoint for toxicological risk assessment. Based on a wide body of research having assessed the effect of various environmental stressors (pharmaceutical residues, metals, carbon dioxide, anti-fouling agents) on the camouflage abilities of juvenile common cuttlefish, we discuss the relevance of this species as a toxicological model and address the challenge of color change quantification and standardization through a comparative review of the available measurement techniques.

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.

Trace elements in the silky shark Carcharhinus falciformis in the Central Pacific Mexican Shelf

Mercury (Hg), cadmium (Cd) and copper (Cu) concentrations were determined in muscle, liver and fin of the silky shark (Carcharhinus falciformis) caught in the Central Pacific Mexican Shelf. Liver tissue presented the highest concentrations of Cd (2.83 μg g^-1 wet weight (ww)) and Cu (2.34 μg g^-1 ww). For muscle and fin, Cu presented the highest concentrations (0.97 and 1.80 μg g^-1 ww, respectively). Liver concentrations were influenced by the maturation stages for the three elements. Immature organisms exhibited lower trace element concentrations than adults. No significant differences were found between sexes, except for Cu concentrations in muscle, where adult females present higher levels than adult males. One muscle sample (2.3 %) exceeded the Mexican Legislation for Hg (1.0 μg g^-1 ww) and five muscles samples (11.6 %) exceeded the Mexican limit for Cd (0.5 μg g^-1 ww). Meat consumption of this species can be a risk to human health if it is ingested regularly.

Trace metal concentrations in California sea lions from rookeries exposed to different levels of coastal urbanization in Baja California, Mexico

Concentrations of total mercury, total selenium, and cadmium ([THg], [TSe], [Cd]) were determined in hair of California sea lion (Zalophus californianus) pups from four islands of the Gulf of California and the Baja California Pacific coast (NG, CG, NP, and CP) to identify geographical differences and the effect of Se against Hg toxicity (TSe:THg molar ratio). THg displayed a strong north-south trend for both ecoregions, while TSe presented a significantly high concentration only for CG. TSe:THg molar ratios decreased when [THg] increased, with the lowest ratios presenting in NG pups, in which [THg] exceeded toxicological thresholds of concern. [Cd] presented similar values at all study sites except CG, which presented the lowest level. The present study shows that proximity to urbanized coastal areas has a strong influence on [THg] in pups, while [TSe] and [Cd] are probably more related to the physiological requirements of the species, and environmental conditions.

Isotopic Niche Analysis of Long-Finned Pilot Whales (Globicephala melas edwardii) in Aotearoa New Zealand Waters

Simple Summary

Isotopic niche analyses can elucidate a species’ foraging ecology. Using isotopic values of δ¹³C, δ¹⁵N and δ³⁴S, the isotopic niche of long-finned pilot whales (Globicephala melas edwardii) in Aotearoa New Zealand was investigated for animals that stranded in six different events across two locations between 2009 and 2017. Generalised additive models revealed that stranding event was a stronger predictor for δ¹³C and δ¹⁵N values than body length, sex, or reproductive status, indicating that spatiotemporal differences explained isotopic variation of G. m. edwardii in New Zealand waters better than ontogenetic factors.

Abstract

The quantification of a species’ trophic niche is important to understand the species ecology and its interactions with the ecosystem it resides in. Despite the high frequency of long-finned pilot whale (Globicephala melas edwardii) strandings on the Aotearoa New Zealand coast, their trophic niche remains poorly understood. To assess the isotopic niche of G. m. edwardii within New Zealand, ontogenetic (sex, total body length, age, maturity status, reproductive group) and spatiotemporal (stranding location, stranding event, and stranding year) variation were investigated. Stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) were examined from skin samples of 125 G. m. edwardii (67 females and 58 males) collected at mass-stranding events at Onetahua Farewell Spit in 2009 (n = 20), 2011 (n = 20), 2014 (n = 27) and 2017 (n = 20) and at Rakiura Stewart Island in 2010 (n = 19) and 2011 (n = 19). Variations in δ³⁴S values were examined for a subset of 36 individuals. General additive models revealed that stranding event was the strongest predictor for δ¹³C and δ¹⁵N values, whilst sex was the strongest predictor of δ³⁴S isotopic values. Although similar within years, δ¹³C values were lower in 2014 and 2017 compared to all other years. Furthermore, δ¹⁵N values were higher within Farewell Spit 2017 compared to any other stranding event. This suggests that the individuals stranded in Farewell Spit in 2017 may have been feeding at a higher trophic level, or that the nitrogen baseline may have been higher in 2017 than in other years. Spatiotemporal differences explained isotopic variation of G. m. edwardii in New Zealand waters better than ontogenetic factors.

Methodological considerations in studying digestive system physiology in octopus: limitations, lacunae and lessons learnt

Current understanding of cephalopod digestive tract physiology is based on relatively “old” literature and a “mosaic of data” from multiple species. To provide a background to the discussion of methodologies for investigating physiology we first review the anatomy of the cephalopod digestive tract with a focus on Octopus vulgaris, highlighting structure-function relationships and species differences with potential functional consequences (e.g., absence of a crop in cuttlefish and squid; presence of a caecal sac in squid). We caution about extrapolation of data on the digestive system physiology from one cephalopod species to another because of the anatomical differences. The contribution of anatomical and histological techniques (e.g., digestive enzyme histochemistry and neurotransmitter immunohistochemistry) to understanding physiological processes is discussed. For each major digestive tract function we briefly review current knowledge, and then discuss techniques and their limitations for the following parameters: 1) Measuring motility in vitro (e.g., spatiotemporal mapping, tension and pressure), in vivo (labelled food, high resolution ultrasound) and aspects of pharmacology; 2) Measuring food ingestion and the time course of digestion with an emphasis on understanding enzyme function in each gut region with respect to time; 3) Assessing transepithelial transport of nutrients; 4) Measuring the energetic cost of food processing, impact of environmental temperature and metabolic rate (flow-through/intermittent respirometry); 4) Investigating neural (brain, gastric ganglion, enteric) and endocrine control processes with an emphasis on application of molecular techniques to identify receptors and their ligands. A number of major knowledge lacunae are identified where available techniques need to be applied to cephalopods, these include: 1) What is the physiological function of the caecal leaflets and intestinal typhlosoles in octopus? 2) What role does the transepithelial transport in the caecum and intestine play in ion, water and nutrient transport? 3) What information is signalled from the digestive tract to the brain regarding the food ingested and the progress of digestion? It is hoped that by combining discussion of the physiology of the cephalopod digestive system with an overview of techniques and identification of key knowledge gaps that this will encourage a more systematic approach to research in this area.

The role of tropical small-scale fisheries in trace element delivery for a Small Island Developing State community, the Seychelles

The concentrations of 13 trace elements were determined in 1032 muscles of 54 small-scale fisheries species collected from the Seychelles waters between 2013 and 2019. Overall, profiles were dominated by zinc (Zn) > arsenic (As) > iron (Fe) > copper (Cu) > selenium (Se), with the spiny lobsters, spanner crab and octopus exhibiting the highest levels of As, Cu and Zn while fish had higher Fe concentrations. Both taxonomy-dependent processes and ecological factors explained the interspecific differences of trace element profiles observed. A benefit-risk assessment revealed that crustaceans and cephalopods were good sources of Cu and Zn. One portion of any fish could provide 30-100 % of daily Se needs, and one portion of demersal and pelagic teleost fish could bring 5-20 % of Cu, Fe and Zn needs, especially for young adult and adult women. Finally, our analysis showed that there was very low health risks associated with small-scale fisheries consumption for the Seychelles population.

Heavy metals and metalloid levels in the tissues of yellow-legged gulls (Larus michahellis) from Spain: sex, age, and geographical location differences

In the present study, mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se), and arsenic (As) were measured in liver, kidney, and feathers of adult, juvenile, and chick seagulls (Larus michahellis) collected from the northwest of Spain. Age, sex, and the geographical location of samples were considered variables that can influence metal bioaccumulation, for which concentrations were determined by means of ICP-MS. The mean concentrations (dry weight) found in seagulls were 7.01 ± 0.37 mg Hg/kg, 22.82 ± 2.83 mg Cd/kg, 7.36 ± 1.36 mg Pb/kg, 18.64 ± 0.63 mg Se/kg, and 10.64 ± 0.59 mg As/kg. Regarding the different factors analyzed, Hg was the only metal showing sex-related differences, being significantly higher (p < 0.05) the concentrations found in feathers of males (1.26 ± 0.12 mg/kg) than those in females (0.99 ± 0.11 mg/kg). A highly significant (p < 0.01) increase in levels of some metals was found in liver related to the increase of age: Hg (adults (A) 3.33 ± 0.22 mg/kg vs chicks (C) 1.76 ± 0.28 mg/kg), Cd (A 4.74 ± 0.62 mg/kg vs C 1.79 ± 0.2), Pb (A 0.65 ± 0.12 mg/kg vs juveniles 0.4 ± 0.11 mg/kg), and Se (A 7.56 ± 0.43 mg/kg vs C 5.24 ± 0.53 mg/kg). Positive correlations between Cd-Hg and Se-Hg were found in liver (p < 0.001), kidney (p < 0.001), and feathers (p < 0.05 and p < 0.001, respectively). The associations found may reflect antagonistic interactions between Se and Cd on Hg toxicity. The results suggest that L. michahellis can reveal local contamination around the foraging and breeding sites and can be a very useful monitoring instrument for assessing heavy metal contamination and sentinel species of environmental health.

Mercury and Cadmium Concentrations in Muscle Tissue of the Blue Shark (Prionace glauca) in the Central Eastern Pacific Ocean

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.

Bioaccumulation of total mercury, copper, cadmium, silver, and selenium in green turtles (Chelonia mydas) stranded along the Potiguar Basin, northeastern Brazil

Sea turtles face several threats and pollution has become a major concern for their conservation worldwide. We analyzed samples of the liver, muscles, and kidneys of 38 Chelonia mydas stranded along the Potiguar Basin, northeastern Brazil, between 2015 and 2018 to determine the total Hg concentration (THg), as well as the concentrations of Cu, Cd, Ag, and Se. The relation between turtle size and element concentrations revealed a negative correlation for THg and Se (liver, muscles, and kidneys), Cu and Cd (liver and kidneys) and a positive correlation for Ag in the three organs analyzed. Concentrations of THg, Cu, Ag, and Se were high in the liver, highlighting the Cu concentration (median = 25.1150 μg g^-1 w.w.), while the kidneys had the highest Cd levels (median = 12.2200 μg g^-1 w.w.). There was significant difference between element concentrations and the three organs analyzed, except for Ag and Se concentrations in the muscle and kidney samples. Our study showed that green turtles found in Potiguar Basin, northeastern Brasil, have bioaccumulated inorganic elements which indicate the need of further investigations on the environmental quality of the region.

Two cetacean species reveal different long-term trends for toxic trace elements in European Atlantic French waters

Cetaceans have been naturally exposed to toxic trace elements (TEs) on an evolutionary time scale. Hence, they have developed mechanisms to control and/or mitigate their toxic effects. These long-lived species located at high trophic positions and bioaccumulating toxic elements are assumed to be good biomonitoring organisms. However, anthropogenic emissions have strongly increased environmental levels of toxic TEs in the last decades, questioning the efficiency of the detoxication mechanisms in cetaceans. In this context, temporal trends of mercury (Hg), cadmium (Cd) and lead (Pb) concentrations were studied through the analysis of 264 individuals from two cetacean species the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena) and belonging to two different Management Units (MUs) for the latter. These individuals stranded along the French Atlantic coasts from 2000s to 2017. All the trends presented were age- and sex-corrected and stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) were measured as proxies of their feeding ecology. Results showed that Pb concentrations clearly decreased over time in both species and MUs. This decrease agrees with the lead petrol regulation after 2000s, supporting the use of these species as valuable bioindicators of changes for TE levels in the marine environment. A significant long-term increase of total Hg concentrations was only observed in common dolphins. Cadmium concentrations also revealed different trends over the period in both species. The different Hg and Cd trends observed in the two species, probably reflected a contrasted contamination of habitat and prey species than a global increase of the contamination in the environment. These results highlight the necessity and gain of using different species to monitor changes in marine environments, each of them informing on the contamination of its own ecological niche. Lastly, the Se:Hg molar ratios of species suggested a low risk for Hg toxicity over time.

Cadmium and lead levels in muscle tissue of blue shark (Prionace glauca) in the Southeastern Pacific Waters

Prionace glauca is a top predator, prone to bioaccumulate trace elements, representing the most captured elasmobranch species for human consumption in Peru. Concentrations of cadmium and lead in the edible muscle tissue of the blue shark captured in the south Peruvian coastal waters and offshore north-central Chile were determined. The Cd and Pb levels varied between 0.004 and 0.014 and 0.004 and 0.03 mg kg^-1, respectively. We found direct correlation of Cd concentration with the total length, nevertheless there was no clear relationship regarding sex, seasons, and capture areas. Both metals were below the safety limits for human consumption. The target hazard quotient (THQ) values suggest that its consumption does not represent a risk to the human health. In Peru, this is only the second paper that reports Cd and Pb in sharks. We recommend increasing the sampling by including larger sharks and in other regions of the Peruvian coastline.

First evidence of the utility of cephalopods for biomonitoring program in the field: case of Sepia officinalis south west of Mediterranean Sea (Gulf of Gabes, Tunisia)

This study was carried out to determine the concentration of selected heavy metals in common cuttlefish (Sepia officinalis) caught in the south west of Mediterranean Sea (Gulf of Gabes, Tunisia). To reach this objective, cuttlefish samples were collected from each area (Sfax and Djerba) situated along the Gulf of Gabes, and the concentrations of heavy metals (Cu, Zn, Pb, and Cd) were measured in the gills, gonads, digestive glands, and muscles. Sample preparation and quantification of the metals were accomplished via the wet digestion method and atomic absorption spectroscopy. The levels of heavy metals varied significantly among organs and sites. In fact, the population from Sfax (Gargour) shows the highest concentrations of copper, zinc, and lead compared to the population from Djerba. Globally, recorded metal concentrations were within the range or below the levels in similar species from other regions across the world. To our knowledge, this study is the first that interests to the bioaccumulation of metals in this cuttlefish species from the two investigated areas and to the evaluation of their levels in different tissues.

Temporal trends of trace elements bioaccumulation by a vulnerable cetacean (Pontoporia blainvillei) before and after one of the largest mining disasters worldwide

One of the largest environmental disasters worldwide occurred on November 5th^, 2015, when the Fundão dam collapsed in Mariana (Minas Gerais State, Southeast Brazil). The tailing mud flooded the Doce River basin and reached the sea in the coast of Espírito Santo State (ES), Southeast Brazil. This coastal region is the habitat of the most isolated population of franciscana dolphins (Pontoporia blainvillei), with the lowest populational census and lowest genetic diversity in Franciscana Management Area Ia (FMA Ia) - 18° 25'S and 21° 17'S. This study aimed to assess the bioaccumulation of trace-elements (As, Cd, Cu, Fe, Hg, Mn, and Zn) in muscle, liver and kidney of franciscana dolphins collected near the Doce River's mouth before (n = 32) and after (n = 19) the tailing mud reached the sea. The Generalized Additive Model (GAM) showed increasing temporal trends of Hg and Zn in muscle and liver after the dam failure, probably related to higher concentrations and bioavailability in the water column and sediments from the Doce River. Declining trends were found for As and Cu muscular and hepatic concentrations and Fe concentrations in kidney due to their lower bioavailability after the disaster, caused by association with tailings mud trapped in the riverbanks and suspended particulate material. Additionally, higher As and Hg concentrations found in the first period of sampling may be due to historical contamination by mining activities. The full extent of the impacts caused by the Fundão dam failure is still unknown. However, due to their rapid increase and remobilization process, toxic effects can be induced in the biota by these elements. Elements' bioaccumulation in this study contributes to the knowledge of franciscana dolphins from FMA Ia. Considering the conservation concern regarding this franciscana population and its scarce knowledge, the impact of this disaster can be alarming for species conservation.

Cleaner seas: reducing marine pollution

In the age of the Anthropocene, the ocean has typically been viewed as a sink for pollution. Pollution is varied, ranging from human-made plastics and pharmaceutical compounds, to human-altered abiotic factors, such as sediment and nutrient runoff. As global population, wealth and resource consumption continue to grow, so too does the amount of potential pollution produced. This presents us with a grand challenge which requires interdisciplinary knowledge to solve. There is sufficient data on the human health, social, economic, and environmental risks of marine pollution, resulting in increased awareness and motivation to address this global challenge, however a significant lag exists when implementing strategies to address this issue. This review draws upon the expertise of 17 experts from the fields of social sciences, marine science, visual arts, and Traditional and First Nations Knowledge Holders to present two futures; the Business-As-Usual, based on current trends and observations of growing marine pollution, and a More Sustainable Future, which imagines what our ocean could look like if we implemented current knowledge and technologies. We identify priority actions that governments, industry and consumers can implement at pollution sources, vectors and sinks, over the next decade to reduce marine pollution and steer us towards the More Sustainable Future.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11160-021-09674-8.

Cleaner seas: reducing marine pollution

In the age of the Anthropocene, the ocean has typically been viewed as a sink for pollution. Pollution is varied, ranging from human-made plastics and pharmaceutical compounds, to human-altered abiotic factors, such as sediment and nutrient runoff. As global population, wealth and resource consumption continue to grow, so too does the amount of potential pollution produced. This presents us with a grand challenge which requires interdisciplinary knowledge to solve. There is sufficient data on the human health, social, economic, and environmental risks of marine pollution, resulting in increased awareness and motivation to address this global challenge, however a significant lag exists when implementing strategies to address this issue. This review draws upon the expertise of 17 experts from the fields of social sciences, marine science, visual arts, and Traditional and First Nations Knowledge Holders to present two futures; the Business-As-Usual, based on current trends and observations of growing marine pollution, and a More Sustainable Future, which imagines what our ocean could look like if we implemented current knowledge and technologies. We identify priority actions that governments, industry and consumers can implement at pollution sources, vectors and sinks, over the next decade to reduce marine pollution and steer us towards the More Sustainable Future.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11160-021-09674-8.

Trace elements in stomach oil of Scopoli's shearwater (Calonectris diomedea) from Linosa's colony

Calonectris diomedea is a colonial Procellariiform breeding on Mediterranean islands. The stomach oil produced during chick rearing is a peculiar trait of this species. The composition of the stomach oil is likely to reflect the composition of the prey ingested and might reveal the contaminants uptake with prey becoming a possible tool for the marine pollution monitoring. We examined the concentration of 15 trace elements by ICP-MS and direct mercury analyser. The principal component analysis revealed a heterogeneous pattern of metal concentration, showing a significant separation between samples collected 20 and 70 days after hatching. The data obtained in this work give preliminary information on the feeding habits and breeding ecology of Linosa's colony of Scopoli's shearwater. The trace metals variability found suggest that the stomach oil may have a role as trophic markers to understand predator-prey relationships and to have evidence on the accumulation of pollutants in the latter.

Metal content in stranded pelagic vs deep-diving cetaceans in the Canary Islands

The Canary Islands are home to many cetacean species, many of which are resident species. The present work aims to analyze, for the first time to the best of the authors' knowledge, the macronutrients, micronutrients and trace elements and toxic heavy metals in muscle and liver tissue of six species of stranded cetaceans in the Canary Islands. The study species were: Tursiops truncatus, Stenella frontalis, Delphinus delphis, Grampus griseus, Globicephala macrorynchus and Physeter macrocephalus. Statistical analysis studied the significant differences between the concentrations in muscle and liver tissues, with the differences in element content depending on the type of diving and length of the species. The results indicate that there are differences between muscle and liver for Ca, Cd, Co, Cu, K, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn. Deep-diving animals differ in their concentrations of Cr, Cu, Mg, Mn, Mo, and Zn with respect to shallow-diving animals in muscle and in liver in Al, B, Cr, K, Mn and Mo. As for the differences between sex, the males present differences in their concentrations of B, Cd, K and Mg in muscle tissue with respect to the females, while differences in the liver were only detected in the Fe content. The study of the correlations shows that as the size of the animal increases, the concentration of Cd increases while the concentrations of Al, Cu and Zn decrease. The specimens foraging in shallower waters had the highest concentration of the macronutrient.

Assessments of metallic contents in rare cephalopods from the Canary Islands: relationships with depth habitat and body size

This study investigated 20 elements in the muscle of 11 cephalopod species caught in the Canary Islands inhabiting from coastal to meso-bathypelagic habitats. Among them, trace element contents from large and elusive cephalopods such as Architeuthis dux, Taningia danae, Lepidoteuthis grimaldii, and Haliphron atlanticus were determined. Statistically significant differences in element concentration were found among class sizes and habitat. Large species that are inhabiting in deepest waters such as Loligo forbesii, A. dux, T. danae, H. atlanticus, and L. grimaldii showed a high load and variability in Fe and Al, while coastal species were characterized by a homogeneous element composition, being the Zn loads highest than other elements. Metal contents in large and elusive cephalopod species were dominated by Fe, Ni, Al, Zn, and Sr, with these species being able to carry important amounts of these elements to predators such as deep-diving odontocetes that reside around the Canary waters.

Year-round element quantification of a wide-ranging seabird and their relationships with oxidative stress, trophic ecology, and foraging patterns

Multidisciplinary approaches are essential to diligently assess environmental health status of ecosystems. In this study, year-round chemical elements' exposure and impacts were assessed on the wide-ranging Cory's shearwater Calonectris borealis breeding in Berlenga Island, offshore Portugal, North Atlantic Ocean. The aim was to identify potential contamination and oxidative stress sources associated with trophic ecology, habitat and spatial use, and foraging patterns. A set of 20 chemical elements were quantified, along with oxidative stress biomarkers, stable isotope analyses, and GPS tracking data. Birds presented higher accumulation to some non-essential elements along the year (i.e. arsenic, As; cadmium, Cd; mercury, Hg; lead, Pb; and strontium, Sr), in which concentrations were similar or surpassed other procellariform seabird populations all over the world. No significant differences were found for any of the elements between different periods within the breeding season, with exception of Hg. However, a Principal Component Analysis taking into consideration a group of elements showed differences between pre-laying and chick-rearing periods, with overall higher concentrations in the former. Individuals spending more time engaging in an intensive search for food, and in more coastal environments, presented overall higher element concentrations, and particularly Hg. Contrary to expectations, no relationships were found between chemical elements and oxidative stress. On the other hand, spatial use and foraging patterns of Cory's shearwaters influenced their oxidative stress responses. Our results highlight the need for multidisciplinary approaches to deepen understanding of the large-scale vulnerability of bioindicators such as seabirds and, by extension, the overall environmental health of ecosystems in which they rely.

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.

Trophic ecology drives trace element concentrations in the Antarctic octopod community

Despite the Antarctic Ocean being considered a pristine environment, elevated trace element concentrations have been reported in many marine organisms. The Antarctic Ocean is particularly vulnerable to climate change, which can also affect the bioaccumulation of trace element concentrations in biota. While Antarctic octopods are key components of the regional food webs as prey for a variety of predators (e.g., seals, fish, and seabirds), their contamination state by trace elements remains largely unknown. This study investigated the trace element concentrations in relation to the trophic ecology in Antarctic octopods. Stable isotope values (δ¹³C and δ¹⁵N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were measured in eight different species (Adelieledone polymorpha, Pareledone aequipapillae, P. albimaculata, P. aurata, P. charcoti, P. cornuta, P. felix, and P. turqueti) sampled near Elephant Island, close to the Antarctic Peninsula. Stable isotopes of δ¹⁵N varied among species, with significant differences between A. polymorpha and P. aurata suggesting potential niche segregation. Trace element concentrations also differed among species and with sampling depth, which likely reflects their trophic ecology. The data presented in this study provides the first insight into the trace element concentrations for these endemic octopods in this vulnerable habitat and their stable isotope values.

Habitat and resource segregation of two sympatric seals in the North Sea

The study of ecological niche segregation in sympatric species is essential to understand ecosystem functioning and its response to potential changes. In the North Sea, sympatric grey and harbour seals may present competition for food resources sustained by intense fishing activities and recent increase of seal populations. In order to coexist and reduce inter-specific competition, sympatric species must segregate at least one aspect of their ecological niches: temporal, spatial or resource segregation. We aim to study the foraging resources and foraging distributions of grey seals and harbour seals and the potential competition between these species in the North Sea. Therefore, we analysed stable isotopic composition of C, N and S (δ¹³C, δ¹⁵N and δ³⁴S values), and the concentrations of Hg and Se in blood of harbour and grey seals from the North Sea. Blood samples were collected on 45 grey seals and 37 harbour seals sampled along German and Scottish coasts. Stable isotope ratios were performed with an isotope ratio mass spectrometer coupled to an N-C-S elemental analyser for automated analyses. Total mercury concentrations (T-Hg) were determined by atomic absorption spectroscopy and Se concentrations by ICP-MS. The multi-tracer approach shown spatial and resource partitioning within grey and harbour seal living along German and Scottish coasts. Data indicate 1) the offshore foraging distribution of grey seals as reflected by the lower δ¹⁵N values and T-Hg concentrations and higher Se concentrations and 2) the inshore foraging distribution of harbour seals because of higher δ¹⁵N values and T-Hg concentrations and lower Se concentrations. The SIAR mixing model revealed 3) a more selective diet of grey seals compared to harbour seals and 4) the importance of sandeels in grey seal diet reflected by their high δ³⁴S values. Lastly, diet ellipse overlaps between grey seals and harbour seals sampled along the German coasts suggested 5) a potential sharing of food resources, possibly due to the increase number of grey seals number in this area during the foraging season - all year except breeding and moulting periods. The multi-tracer approach of this study provides a more robust discrimination among diet resources and spatial foraging distributions of grey seals and harbour seals in the North Sea.

Trace element concentrations, including Cd and Hg, in long-finned pilot whales (Globicephala melas edwardii) mass stranded on the New Zealand coast

The Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii) is a top predator in the New Zealand pelagic food web, feeding predominantly on arrow squids. This study quantified trace element concentrations (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, V, Zn) in four tissues (blubber, kidney, liver, muscle) from 21 individuals from stranding sites in New Zealand. Maximum Cd and Hg concentrations were measured in liver and kidney, respectively. Selenium had a positive correlation with Cd and Hg, suggesting the involvement of Se in Cd and Hg detoxification. Arrow squids from the whales' stomach contents were DNA barcoded and identified as Nototodarus sloanii. Trace element concentrations were measured in squid samples from the whale stomach contents. The significant correlation for Hg between the squid tissue and the whale tissue suggests that arrow squids play a major role in trace element uptake by G. m. edwardii.

Mercury in the tissues of five cephalopods species: First data on the nervous system

Mercury (Hg), one of the elements most toxic to biota, accumulates within organisms throughout their lifespan and biomagnifies along trophic chain. Due to their key role in marine systems, cephalopods constitute a major vector of Hg in predators. Further, they grow rapidly and display complex behaviours, which can be altered by neurotoxic Hg. This study investigated Hg concentrations within 81 cephalopod specimens sampled in the Bay of Biscay, which belonged to five species: Eledone cirrhosa, Sepia officinalis, Loligo vulgaris, Todaropsis eblanae and Illex coindetii. Hg concentrations were measured in the digestive gland, the mantle muscle and the optic lobes of the brain. The digestive gland and the mantle were tissues with the most concentrated Hg among all species considered (up to 1.50 μg.g^-1 dw), except E. cirrhosa. This benthic cephalopod had 1.3-fold higher Hg concentrations in the brain (up to 1.89 μg.g^-1 dw) than in the mantle, while other species had 2-fold lower concentrations of Hg in the brain than in the mantle. Brain-Hg concentrations can be predicted from muscle-Hg concentrations for a given species, which facilitates the assessment of Hg toxicokinetics in cephalopods. In the most contaminated E. cirrhosa individual, the chemical form of Hg in its digestive gland, mantle muscle and optic lobes, was determined using High energy-Resolution X-ray Absorption Near Edge Structure (HR XANES) spectroscopy. In the digestive gland, 33 ± 11% of total Hg was inorganic Hg speciated as a dicysteinate complex (Hg(Cys)₂), which suggested that the demethylation of dietary MeHg occurs in this organ. All Hg found in the mantle muscle and the optic lobes is methylated and bound to one cysteinyl group (MeHgCys complex), which implies that dietary MeHg is distributed to these tissues via the bloodstream. These results raised the questions regarding interspecific differences observed regarding Hg brain concentrations and the possible effect of Hg on cephalopod functional brain plasticity and behaviour.

Metal contamination in threatened elasmobranchs from an impacted urban coast

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

Profile and consumption risk assessment of trace elements in megamouth sharks (Megachasma pelagios) captured from the Pacific Ocean to the east of Taiwan

Focusing on 27 rare filter-feeding megamouth sharks (Megachasma pelagios) captured as a by-catch of drift gillnet fishery in the Pacific Ocean to the east of Taiwan, this study analyzes the concentrations of 24 elements in their muscle, discusses the bioaccumulation of each element and the correlation between different elements, and assesses the potential health risks of consuming megamouth shark muscle. Among the 24 elements, mean concentrations of Ga, Ag, Li, Bi, Hg, Co, and Cd were relatively low ranging from 10^-3 to 10^-1 mg/kg, those of Pb, Ba, Mn, Ni, As, Cr, B, Sr, Cu, and Zn ranged from 10^-1-10¹ mg/kg, and those of Fe, Ca, Al, K, Mg, Ti, and Na were relatively high ranging from 10¹ to 10³ mg/kg. The toxic element content index was most significantly correlated with the concentration of Cu. Hence, this study recommends that the concentration of Cu could be used as an indicator of metal accumulation in megamouth shark muscle. The log bioconcentration factor (BCF) ranged from less than 0 to 7.85 in shark muscle. For elements with a concentration of less than 100 μg/L in seawater, the log BCF was inversely proportional to their concentration in seawater. According to the correlation analysis, the accumulation of elements in muscle of megamouth sharks is primarily affected by the concentrations of dissolved elements in seawater, except that the accumulation of Hg, As, Cu, Ti, Al, and Fe appears to be mainly affected by feeding behaviors. The assessment of the health risk of consuming megamouth shark muscle showed that its total hazard index was greater than 1. This suggests that the long-term or high-frequency consumption of megamouth shark muscle may cause health hazards due to the accumulation of trace elements, particularly those with a large contribution of health risk, including As, Hg, and Cu.

Antarctic Adélie penguin feathers as bio-indicators of geographic and temporal variations in heavy metal concentrations in their habitats

Seabird feathers are effective indicators of heavy metal contamination. To propose a biological detection method suitable for the long-term monitoring of heavy metals in the Antarctic environment, eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in Adélie penguin feathers from different body parts, years, and molting grounds in the Antarctic were investigated in this study. It is found that the concentrations of heavy metals in the feathers showed differences among the body part of origin. The levels of the eight elements in the abdomen and back feathers were approximately the same, but some elements of them were significantly higher than those in the tail feathers. The Hg and Cd concentrations in the abdomen and back feathers increased from root to tip, regardless of the sampling year or molting ground. Based on a structural analysis of the feathers, Hg and Cd were mainly distributed in the feather vane rather than the shaft. The methylmercury content accounted for 83%-97% of the total mercury content in all feather samples, regardless of location, year, or body part, thereby supporting the assumption that mercury entering the feather was predominantly methylated and indicating that a relatively toxic form of Hg is excreted through the feathers. The heavy metals in feathers from the same molting ground showed significant differences over the sampling years. The average concentrations of As, Cr, Cu, Ni, and Zn increased significantly from 2015 to 2019, whereas those of Cd, Hg, and Pb tended to decrease. The concentrations of the eight elements in Adélie feathers from three molting grounds varied greatly, possibly in relation to their living areas and dietary structures. Feathers from the Ross Sea site had the highest Cd, Cu, Hg, Ni, and Zn concentrations, the highest As and Cr concentrations were detected in feathers from the Zhongshan site, and feathers from the Great Wall site showed higher Pb concentrations than those from the other two sites. This study established a long-term, nondestructive, and efficient method for monitoring heavy metal contamination in the polar environment in the future.

Mercury concentrations in the tissues of blue shark (Prionace glauca) from Sagami Bay and cephalopods from East China Sea

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.

First report of heavy metal presence in muscular tissue of loggerhead turtles Caretta caretta (Linnaeus, 1758) from the Balearic Sea (Balearic Islands, Spain)

The concentrations of cadmium (Cd), mercury (Hg) and lead (Pb) were determined in muscular tissue of eleven loggerhead turtles (Caretta caretta) from the Balearic Islands (Spain, Western Mediterranean). The metal levels found in the present study were similar or lower than concentrations detected in Andalusia (mainland Spain), Italy, Canary Islands (Spain) or Japan. As the main source of metals in the loggerhead turtle is the diet, low metal burdens could be explained by its opportunistic feeding way. No significant differences were found in metal concentrations between juveniles and subadults in any of the heavy metals analysed. Furthermore, no significant correlation was detected between heavy metal concentrations and straight carapace length (SCL) of the studied individuals. These results could derive from the homogeneity in age and size of the turtles sampled, so further studies including adults are needed in order to assess the heavy metal accumulation with turtle growth.

Mercury bioaccumulation in the long-fin squid Loligo forbesi near the Mid-Atlantic Ridge: Implications to human exposure

Due to growing commercial interest as a fishing resource and its intermediate position in the marine trophic chains as both prey and predator, cephalopods can play an important role in mercury (Hg) transfer along the marine food webs, since they can bioaccumulate this metal in its tissues. Our study aims to analyze Hg accumulation in Loligo forbesi caught in the Azores Archipelago (Portugal) quantifying Hg in different tissues (mantle and stomach), as well in the squid stomach content, in order to evaluate the efficiency of Hg transfer from prey to predator. Hg data from the tissues was used to estimate the weekly tolerable Hg intake due to squid consumption. Overall data indicate that Hg measured in the stomach tissue (0.1 ± 0.01 μg g^-1) was significantly higher than Hg levels found in the mantle (0.04 ± 0.001 μg g^-1) and stomach contents (0.01 ± 0.001 μg g^-1). BMF (bioaccumulation factor) was >1 for all the samples, indicating a biomagnification process from prey to predator. Hg concentration in the mantle tissue was correlated with mantle size; although females present higher Hg levels than males, the difference was found to be not related to gender but rather to the fact that females had larger bodies. Finally, considering the Hg concentration found in the mantle and the permitted Hg levels, it is advisable to consume up to 1050-1890g of squid per week, according to the regulatory agencies. Thus, our results indicate that, since these doses are respected, consumption of squids from the Azorean waters do not pose a risk to humans.

Regional assessment of trace element concentrations in arrow squids (Nototodarus gouldi, N. sloanii) from New Zealand waters: Bioaccessibility and impact on food web and human consumers

The New Zealand arrow squids, Nototodarus gouldi and N. sloanii, play an important role in the marine food web, and are both economically important fishery species. This study compares trace element concentrations (As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Mn, Pb, U, and Zn) in these animals from different fishing locations within New Zealand's Exclusive Economic Zone (Auckland Islands, Chatham Rise, Dunedin, Golden Bay, Taranaki, and West Coast of the South Island). Muscular mantle (the tissue usually consumed by humans) and digestive gland tissue (the primary organ for trace element accumulation) concentrations were compared among regions, revealing size, species, and sampling location effects. Overall, N. gouldi had higher concentrations of As and Zn. The Taranaki region had the highest concentrations for Cd, Co, Cu, and Zn in both tissues analysed. To assess the bioaccessibility of these trace elements to humans, an in-vitro digestion simulation experiment was conducted, revealing bioavailable concentrations overall below the maximum levels presently considered tolerable for human consumption. However, the in-vitro digestion had no observable effect upon Cd concentrations in arrow squid mantle tissue (implying that the measured concentrations are bioaccessible to humans), and revealed that Cd had the highest potential impact on marine food webs and human health. Digestive gland concentrations in particular indicate that arrow squids can be considered important vectors for trace element transfer to top predators (mean concentration for Cd: 123 ± 148 μg g^-1 dw), with region-specific differences.

Linking cadmium and mercury accumulation to nutritional intake in common dolphins (Delphinus delphis) from Patagonia, Argentina

Bioaccumulation of Hg and Cd from food is a complex ecological process that has been oversimplified in the past. Common dolphins (Delphinus delphis) provide a powerful model to biomonitor metal concentrations in marine environments worldwide. We combined proportions-based nutritional geometry with metal analysis, stomach content analysis and the proximate composition of prey, to yield novel insights into the accumulation of Hg and Cd. Our analysis showed an age-related accumulation trend for Cd and Hg in kidney and liver, with highest concentrations found at 18 years of age. When viewed through the lens of nutritional ecology, Argentine anchovy (58.1 Mass %) and South American long-finned squid (22.7 Mass %), provided most of the dietary intake of protein (P) and lipids (L) (P:L ratio = 2.6:1.0) and also represented the main source for Cd and Hg levels accumulated in their bodies. This study presents unprecedented evidence on metal accumulation in relation to age and nutritional intake in a marine predator.