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Lead (Pb) is a trace element that is naturally present in arid regions but it is also released to the marine environment by anthropogenic industrial emissions. Here, we assessed Pb concentrations in bone samples of four pinniped species: the Galapagos sea lion Zalophus wollebaeki , sampled in Galapagos archipelago, the monk seal Monachus monachus from Mauritania, and the South American fur seal Arctocephalus australis and the South American sea lion Otaria flavescens , from Uruguay, and investigate potential geographic differences. Concentrations of lead in the samples from Galapagos were lower than those detected in samples from Mauritania and Uruguay, indicating that the Galapagos archipelago is a comparatively pristine spot for this toxic element as related to the other two areas. The waters of Mauritania and Uruguay are likely affected by the inputs of lead brought by the desert dust and released by the local industry, respectively. This study supports the use of bone to assess lead concentrations in biota, as well as the use of pinnipeds as bioindicators of marine pollution. [Display omitted] • Lead was analysed in the bone of four pinniped species from three marine areas. • The lowest lead concentrations occurred in pinnipeds from the Galapagos archipelago. • Lead concentrations were higher in pinnipeds from Mauritania and Rio de la Plata. • In Mauritanian waters, the likely origin of lead was wind-brought Sahara dust. • In Rio de la Plata waters, the likely origin of lead was industrial activities. [ABSTRACT FROM AUTHOR]

The Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals, with only 600–700 individuals restricted to three populations off the coast of Western Sahara and Madeira (North Atlantic) and between Greece and Turkey (eastern Mediterranean). Its original range was from the Black Sea (eastern Mediterranean) to Gambia (western African coast), but was drastically reduced by commercial hunting and human persecution since the early stages of marine exploitation. We here analyse 42 mitogenomes of Mediterranean monk seals, from across their present and historical geographic ranges to assess the species population dynamics over time. Our data show a decrease in genetic diversity in the last 200 years. Extant individuals presented an almost four-fold reduction in genetic diversity when compared to historical specimens. We also detect, for the first time, a clear segregation between the two North Atlantic populations, Madeira and Cabo Blanco, regardless of their geographical proximity. Moreover, we show the presence of historical gene-flow between the two water basins, the Atlantic Ocean and the Mediterranean Sea, and the presence of at least one extinct maternal lineage in the Mediterranean. Our work demonstrates the advantages of using full mitogenomes in phylogeographic and conservation genomic studies of threatened species. [ABSTRACT FROM AUTHOR]

• C37 alkenones are transferred through the pelagic trophic web. • Alkenones can be detected in pelagic top predators, but not in coastal ones. • The Uk' 37 appears consistent with the sea surface temperature in the epipelagic species. The alkenones C 37:2 and C 37:3 are produced exclusively by some haptophyte species. Their relative proportion (Uk' 37 index) may be used to infer the water temperature where the synthesising haptophyte lived. Alkenones have been analysed in sediments, planktonic communities and in the low trophic level, filter-feeding fin whales. However, it is unclear whether they can be detected in animals exploiting high trophic levels and used to infer the water temperature in which they live. Alkenones were analysed in blubber samples from three Mediterranean predatory species: the striped dolphin, an epipelagic species; the Risso's dolphin, a deep diver; and the bottlenose dolphin, a coastal species. Alkenones were detected in all striped dolphin samples and in most of the Risso's dolphin samples, but they were below detection limits in the bottlenose dolphin samples. The inferred temperature for the striped dolphins (16.4 ± 3.3 °C) was similar to the average water temperature of the region (16.9 ± 3.9 °C), but that for the Risso's dolphins was lower than expected (12.7 ± 4.4 °C). The small sample sizes and the large variance in the Uk' 37 index make it difficult to ascertain if the dissimilarity between the two oceanic species is real. Although further research is needed to calibrate this bio-indicator, we can conclude that alkenones are transferred through the trophic web and are found in oceanic cetaceans situated at a high trophic level. [ABSTRACT FROM AUTHOR]