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Chemical pollution is a major threat to marine ecosystems, and top predators such as most shark species are extremely vulnerable to being exposed and accumulating contaminants such as metals and persistent organic pollutants (POPs). This work aimed to study the degree, composition, and the sources of contamination in the blue shark (Prionace glauca) inhabiting the Northeast Atlantic, as well as the potential risk faced by human consumers. A total of 60 sharks were sampled in situ aboard fishing vessels, and the concentrations of a set of metals and POPs were analysed in various tissues and complemented with stable isotope analyses. High levels of contaminants were found in most sharks sampled. The concentrations of most metals were higher in the muscle when compared with the liver. Regarding the dangers to consumers posed by the concentrations of arsenic (As), mercury (Hg), and lead (Pb), over 75% of the sharks presented muscle concentrations of at least one contaminant above the legal limits for human consumption, and a risk assessment determined that consumption of meat of these sharks exceeding 0.07 Kg per week could potentially expose human consumers to dangerous amounts of methylmercury (MeHg). Additionally, the assessment of single contaminants may lead to an underestimation of the risk for the human health. Finally, the overall accumulation of contaminants seems to be mostly influenced by the sharks’ geographical distribution, rather than sex, size, or trophic level of their prey.

The Humboldt Current System presents high interannual variability, influenced by the El Niño Southern Oscillation (ENSO), whose implications in wildlife are not fully understood. We studied the isotopic niche of wild Humboldt penguins at Punta San Juan (Peru) during the pre-moult foraging trip in 4 consecutive years (2008–2011) under known oceanographic (ENSO) conditions. Our results show that there is a clear isotopic niche segregation (on both δ13C and δ15N values) of wild Humboldt penguins among all years. Besides isotopic niche segregation, niche width also varied significantly among years. The larger isotopic niche displayed in 2008 reflected the opportunistic feeding behaviour of Humboldt penguins when oceanographic conditions were unfavourable (i.e. El Niño of strong intensity). In contrast, and despite strong segregation, penguins displayed a more specialist behaviour in years of mild environmental conditions (i.e. 2009 “warm-weak”, 2010 “neutral” and 2011 “warm-moderate”). No evidence of sexual segregation in wild Humboldt penguins during the pre-moulting foraging trip was found. This study highlights the coping mechanisms of an endangered species to changes in environmental conditions (i.e. overall, from strong to neutral El Niño events), which should have important ramifications in the management of the marine ecosystem in Peru, particularly the one related to the anchovy industry.

Sympatry can lead to higher competition under climate change and other environmental pressures, including in South Georgia, Antarctica, where the two most common octopod species, Adelieledone polymorpha and Pareledone turqueti, occur side by side. Since cephalopods are typically elusive animals, the ecology of both species is poorly known. As beaks of cephalopods are recurrently found in top predator's stomachs, we studied the feeding ecology of both octopods through the evaluation of niche overlapping and specific beak adaptations that both species present. A multidisciplinary approach combining carbon (δ13C) and nitrogen (δ15N) stable isotope signatures, mercury (Hg) analysis and biomaterials' engineering techniques was applied to investigate the beaks. An isotopic niche overlap of 95.6% was recorded for the juvenile stages of both octopod species, dropping to 19.2% for the adult stages. Both A. polymorpha and P. turqueti inhabit benthic ecosystems around South Georgia throughout their lifecycles (δ13C: −19.21 ± 1.87‰, mean ± SD for both species) but explore trophic niches partially different during adult life stages (δ15N: 7.01 ± 0.40‰, in A. polymorpha, and 7.84 ± 0.65‰, in P. turqueti). The beaks of A. polymorpha are less dense and significantly less stiff than in P. turqueti. Beaks showed lower mercury concentration relative to muscle (A. polymorpha - beaks: 0.052 ± 0.009 μg g−1, muscle: 0.322 ± 0.088 μg g−1; P. turqueti - beaks: 0.038 ± 0.009 μg g−1; muscle: 0.434 ± 0.128 μg g−1). Overall, both octopods exhibit similar habitats but different trophic niches, related to morphology/function of beaks. The high Hg concentrations in both octopods can have negative consequences on their top predators and may increase under the present climate change context.

This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats.

Polar marine ecosystems have global ecological and economic importance because of their unique biodiversity and their major role in climate processes and commercial fisheries, among others. Portugal and Spain have been highly active in a wide range of disciplines in marine biology of the Antarctic and the Arctic. The main aim of this paper is to provide a synopsis of some of the results and initiatives undertaken by Portuguese and Spanish polar teams within the field of marine sciences, particularly on benthic and pelagic biodiversity (species diversity and abundance, including microbial, molecular, physiological and chemical mechanisms in polar organisms), conservation and ecology of top predators (particularly penguins, albatrosses and seals), and pollutants and evolution of marine organisms associated with major issues such as climate change, ocean acidification and UV radiation effects. Both countries have focused their polar research more in the Antarctic than in the Arctic. Portugal and Spain should encourage research groups to continue increasing their collaborations with other countries and develop multi-disciplinary research projects, as well as to maintain highly active memberships within major organizations, such as the Scientific Committee for Antarctic Research (SCAR), the International Arctic Science Council (IASC) and the Association of Polar Early Career Scientists (APECS), and in international research projects.