The whale shark (Rhincodon typus) is an endangered species that may be exposed to micro- and macro-plastic ingestion as a result of their filter-feeding activity, particularly on the sea surface. In this pilot project we perform the first ecotoxicological investigation on whale sharks sampled in the Gulf of California exploring the potential interaction of this species with plastic debris (macro-, micro-plastics and related sorbed contaminants). Due to the difficulty in obtaining stranded specimens of this endangered species, an indirect approach, by skin biopsies was used for the evaluation of the whale shark ecotoxicological status. The levels of organochlorine compounds (PCBs, DDTs), polybrominated diphenyl ethers (PBDEs) plastic additives, and related biomarkers responses (CYP1A) were investigated for the first time in the whale shark. Twelve whale shark skin biopsy samples were collected in January 2014 in La Paz Bay (BCS, Mexico) and a preliminary investigation on microplastic concentration and polymer composition was also carried out in seawater samples from the same area. The average abundance pattern for the target contaminants was PCBs>DDTs>PBDEs>HCB. Mean concentration values of 8.42ng/g w.w. were found for PCBs, 1.31ng/g w.w. for DDTs, 0.29ng/g w.w. for PBDEs and 0.19ng/g w.w. for HCB. CYP1A-like protein was detected, for the first time, in whale shark skin samples. First data on the average density of microplastics in the superficial zooplankton/microplastic samples showed values ranging from 0.00items/m3 to 0.14items/m3. A focused PCA analysis was performed to evaluate a possible correlation among the size of the whale sharks, contaminants and CYP1A reponses. Further ecotoxicological investigation on whale shark skin biopsies will be carried out for a worldwide ecotoxicological risk assessment of this endangerd species.

Are whale sharks exposed to persistent organic pollutants and plastic pollution in the Gulf of California (Mexico)? First ecotoxicological investigation using skin biopsies

Are concentrations of pollutants in sharks, rays and skates (Elasmobranchii) a cause for concern? A systematic review.

Climate change is leading to northward shifts in species distributions that is altering interspecific interactions at low- and mid-trophic levels. However, little attention has been focused on the effects of redistributions of species on the trophic ecology of a high trophic-level predator assemblage. Here, during a 22-year period (1990–2012) of increasing sea temperature (1.0°C) and decreasing sea ice extent (12%) in Cumberland Sound, Nunavut, Canada, we examined the trophic structure of a near-apex predator assemblage before (1990–2002) and after (2005–2012) an increase in the availability of capelin—generally an indicator species in colder marine environments for a warming climate. Stable isotopes (δ 13 C and δ 15 N) were used in a Bayesian framework to assess shifts in diet, niche size and community-wide metrics for beluga whales ( Delphinapterus leucas ), ringed seals ( Pusa hispida ), Greenland halibut ( Reinhardtius hippoglossoides ) and anadromous Arctic char ( Salvelinus alpinus ). After 2005, consumption of forage fish increased for all predator species, suggesting diet flexibility with changing abiotic and biotic conditions. An associated temporal shift from a trophically diverse to a trophically redundant predator assemblage occurred where predators now play similar trophic roles by consuming prey primarily from the pelagic energy pathway. Overall, these long-term ecological changes signify that trophic shifts of a high trophic-level predator assemblage associated with climate change have occurred in the Arctic food web.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.180259

A temporal shift in trophic diversity among a predator assemblage in a warming Arctic.

A rigorous synthesis of the sea-ice ecosystem and linked ecosystem services highlights that the sea-ice ecosystem supports all 4 ecosystem service categories, that sea-ice ecosystems meet the criteria for ecologically or biologically significant marine areas, that global emissions driving climate change are directly linked to the demise of sea-ice ecosystems and its ecosystem services, and that the sea-ice ecosystem deserves specific attention in the evaluation of marine protected area planning. The synthesis outlines (1) supporting services, provided in form of habitat, including feeding grounds and nurseries for microbes, meiofauna, fish, birds and mammals (particularly the key species Arctic cod, Boreogadus saida, and Antarctic krill, Euphausia superba, which are tightly linked to the sea-ice ecosystem and transfer carbon from sea-ice primary producers to higher trophic level fish, mammal species and humans); (2) provisioning services through harvesting and medicinal and genetic resources; (3) cultural services through Indigenous and local knowledge systems, cultural identity and spirituality, and via cultural activities, tourism and research; (4) (climate) regulating services through light regulation, the production of biogenic aerosols, halogen oxidation and the release or uptake of greenhouse gases, for example, carbon dioxide. The ongoing changes in the polar regions have strong impacts on sea-ice ecosystems and associated ecosystem services. While the response of sea-ice - associated primary production to environmental change is regionally variable, the effect on ice-associated mammals and birds is predominantly negative, subsequently impacting human harvesting and cultural services in both polar regions. Conservation can help protect some species and functions. However, the key mitigation measure that can slow the transition to a strictly seasonal ice cover in the Arctic Ocean, reduce the overall loss of sea-ice habitats from the ocean, and thus preserve the unique ecosystem services provided by sea ice and their contributions to human well-being is a reduction in carbon emissions.

/pdf/climate-change-impacts-on-sea-ice-ecosystems-and-associated-3f6aguw5o0.pdf

Climate change impacts on sea-ice ecosystems and associated ecosystem services

Polar bears (Ursus maritimus) rely upon Arctic sea ice as a physical habitat. Consequently, conservation assessments of polar bears identify the ongoing reduction in sea ice to represent a significant threat to their survival. However, the additional role of sea ice as a potential, indirect, source of energy to bears has been overlooked. Here we used the highly branched isoprenoid lipid biomarker-based index (H-Print) approach in combination with quantitative fatty acid signature analysis to show that sympagic (sea ice-associated), rather than pelagic, carbon contributions dominated the marine component of polar bear diet (72-100%; 99% CI, n = 55), irrespective of differences in diet composition. The lowest mean estimates of sympagic carbon were found in Baffin Bay bears, which were also exposed to the most rapidly increasing open water season. Therefore, our data illustrate that for future Arctic ecosystems that are likely to be characterised by reduced sea ice cover, polar bears will not only be impacted by a change in their physical habitat, but also potentially in the supply of energy to the ecosystems upon which they depend. This data represents the first quantifiable baseline that is critical for the assessment of likely ongoing changes in energy supply to Arctic predators as we move into an increasingly uncertain future for polar ecosystems.

/pdf/high-contributions-of-sea-ice-derived-carbon-in-polar-bear-3nxj2zuhrs.pdf

High contributions of sea ice derived carbon in polar bear (Ursus maritimus) tissue.

Trophic position and body mass are traits commonly used to predict organochlorine burdens. Sharks, however, have a variety of feeding and life history strategies and metabolize lipid uniquely. Because of this diversity, and the lipid-association of organochlorines, the dynamics of organochlorine accumulation in sharks may be predicted ineffectively by stable isotope-derived trophic position and body mass, as is typical for other taxa. The present study compared ontogenetic organochlorine profiles in the dusky shark (Carcharhinus obscurus) and white shark (Carcharodon carcharias), which differ in metabolic thermoregulation and trophic position throughout their ontogeny. Although greater organochlorine concentrations were observed in the larger bodied and higher trophic position white shark (e.g., p,p′-dichlorodiphenyldichloroethylene: 20.2 ± 2.7 ng/g vs 9.3 ± 2.2 ng/g in the dusky shark), slopes of growth-dilution corrected concentrations with age were equal to those of the dusky shark. Similar ontogenetic trophic position increases in both species, less frequent white shark seal predation than previously assumed, or inaccurate species-specific growth parameters are possible explanations. Inshore habitat use (indicated by δ13C values) and mass were important predictors in white and dusky sharks, respectively, of both overall compound profiles and select organochlorine concentrations. The present study clarified understanding of trophic position and body mass as reliable predictors of interspecific organochlorine accumulation in sharks, whereas regional endothermy and diet shifting were shown to have less impact on overall rates of accumulation. Environ Toxicol Chem 2015;34:2051–2060. © 2015 SETAC

Comparative organochlorine accumulation in two ecologically similar shark species (Carcharodon carcharias and Carcharhinus obscurus) with divergent uptake based on different life history

Pinnipeds (Carnivora: Mammalia) and sharks (Elasmobranchii: Chondrichthyes) are both widely distributed marine top predators that occupy similar ecological niches. We examined global species diversity patterns of sharks (294 species) and pinnipeds (34 species) as a function of latitude. We then used body size and trophic position (TP) to test which relationship best described the global distributional pattern of species richness between the two clades: (1) pinniped as predator, (2) pinniped as competitor, or (3) pinniped as prey. Ecological relationships between the two species groups were diverse with some larger sharks actively consuming pinnipeds and some smaller shark species eaten by pinnipeds. Most sharks (81%) overlaped with pinnipeds for TP (3.3-4.3), however most sharks are smaller than pinnipeds (62% less than 128 cm maximum length), and only 8% of sharks (24) are longer than the largest pinniped. Latitudinal variation of sharks and pinnipeds indicated that species richness of pinnipeds was bimodally higher at temperate latitudes and lowest at equatorial latitudes between +40 and -40, the geographic region where shark species richness was greatest. A comparison of the three trophic models indicated that the predation model (sharks eat pinnipeds) best fit the distributional pattern. Oceanic regions that supported progressively more than 20 shark species resulted in progressively fewer pinniped species. Results suggest that sharks may exclude pinnipeds from much of the warmer oceanic waters through direct predation. However, an alternate hypothesis that differing thermal adaptations of the two clades may explain the observed distributional pattern is not refuted by our results. We discuss conservation implications associated with ocean warming assuming shark species distribution will expand to higher latitudes, likely at the expense of pinnipeds. [JMATE. 2014;7(1):23-39]

The ghosts of competition past: body size, trophic ecology, diversity and distribution of global shark and pinniped species

Trophic position and body mass are traits commonly used to predict organochlorine burdens. Sharks, however, have a variety of feeding and life history strategies and metabolize lipid uniquely. Because of this diversity, and the lipid-association of organochlorines,thedynamicsoforganochlorineaccumulationinsharksmaybepredictedineffectivelybystableisotope-derivedtrophic position and body mass, as is typical for other taxa. The present study compared ontogenetic organochlorine profiles in the dusky shark (Carcharhinus obscurus) and white shark (Carcharodon carcharias), which differ in metabolic thermoregulation and trophic position throughout their ontogeny. Although greater organochlorine concentrations were observed in the larger bodied and higher trophic position white shark (e.g., p,p 0 -dichlorodiphenyldichloroethylene: 20.2 � 2.7ng/g vs 9.3 � 2.2ng/g in the dusky shark), slopes of growth-dilution corrected concentrations with age were equal to those of the dusky shark. Similar ontogenetic trophic position increases in both species, less frequent white shark seal predation than previously assumed, or inaccurate species-specific growth parameters are possible explanations. Inshore habitat use (indicated by d 13 C values) and mass were important predictors in white and dusky sharks, respectively, of both overall compound profiles and select organochlorine concentrations. The present study clarified understanding of trophic position and body mass as reliable predictors of interspecific organochlorine accumulation in sharks, whereas regional endothermyanddietshiftingwereshowntohavelessimpactonoverallratesofaccumulation.EnvironToxicolChem2015;9999:1-10.© 2015 SETAC

Environmental Toxicology COMPARATIVE ORGANOCHLORINE ACCUMULATION IN TWO ECOLOGICALLY SIMILAR SHARK SPECIES (CARCHARODON CARCHARIAS AND CARCHARHINUS OBSCURUS) WITH DIVERGENT UPTAKE BASED ON DIFFERENT LIFE HISTORY

Sub-Arctic habitats are being exposed to increasingly long periods of open water as sea ice continues to decline in thickness and extent. Some hypothesize that this will result in a reduction, and maybe total loss of sea ice derived (sympagic) carbon supply; however, the impact of such change on ecosystems requires further investigation. Here, we used the H-Print biomarker approach that utilizes well-defined indicators of both sympagic and phytoplanktic carbon, in combination with stable isotopes (δ15N), to study the effect of reducing sympagic carbon availability on beluga whales (Delphinapterus leucas) in the sub-Arctic ecosystem of Cumberland Sound. Our data show that decreasing δ15N in belugas was negatively correlated with pelagic carbon (H-Print) within their diet. We also identified a statistically significant (R2 = 0.82; p ≤ 0.01) change point in the proportion of sympagic/pelagic carbon within beluga around the year 2000, signified by consistently reducing δ15N, coupled with increasing pelagic carbon composition. This observed shift from sympagic to pelagic contribution to diet is likely to remain a feature of the Cumberland Sound ecosystem during the projected reduction of sea ice.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.1002/lno.10520

Coupled changes between the H‐Print biomarker and δ15N indicates a variable sea ice carbon contribution to the diet of Cumberland Sound beluga whales

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Comparative organochlorine accumulation in two ecologically similar shark species (Carcharodon carcharias and Carcharhinus obscurus) with divergent uptake based on different life history

The ghosts of competition past: body size, trophic ecology, diversity and distribution of global shark and pinniped species

Environmental Toxicology COMPARATIVE ORGANOCHLORINE ACCUMULATION IN TWO ECOLOGICALLY SIMILAR SHARK SPECIES (CARCHARODON CARCHARIAS AND CARCHARHINUS OBSCURUS) WITH DIVERGENT UPTAKE BASED ON DIFFERENT LIFE HISTORY

Coupled changes between the H‐Print biomarker and δ15N indicates a variable sea ice carbon contribution to the diet of Cumberland Sound beluga whales