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- Ahlgren, Hans, 1984-, et al.
(author)
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The Baltic grey seal : A 9000-year history of presence and absence
- 2022
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In: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 32:6, s. 569-577
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Journal article (peer-reviewed)abstract
- The grey seal (Halichoerus grypus) has been part of the Baltic Sea fauna for more than 9000 years and has ever since been subjected to extensive human hunting, particularly during the early phases of its presence in the Baltic Sea, but also in the early 20th century. In order to study their temporal genetic structure and to investigate whether there has been a genetically continuous grey seal population in the Baltic, we generated mitochondrial control region data from skeletal remains from ancient grey seals from the archaeological sites Stora Förvar (Sweden) and Neustadt (Germany) and compared these with modern grey seal data. We found that the majority of the Mesolithic grey seals represent haplotypes that is not found in contemporary grey seals, indicating that the Baltic Sea population went extinct, likely due to human overexploitation and environmental change. We hypothesize that grey seals recolonised the Baltic Sea from the North Sea. during the Bronze Age or Iron Age, and that the contemporary Baltic grey seal population is direct descendants of this recolonisation. Our study highlights the power of biomolecular archaeology to understand the factors that shape contemporary marine diversity.
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| 2. |
- Glykou, Aikaterini, et al.
(author)
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Reconstructing the ecological history of the extinct harp seal population of the Baltic Sea
- 2021
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 251
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Journal article (peer-reviewed)abstract
- The harp seal (Pagophilus groenlandicus), today a subarctic species with breeding populations in the White Sea, around the Jan Mayen Islands and Newfoundland, was a common pinniped species in the Baltic Sea during the mid- and late Holocene. It is puzzling how an ice dependent species could breed in the Baltic Sea during the Holocene Thermal Maximum (HTM), and it remains unclear for how long harp seals bred in the Baltic Sea and when the population became extirpated. We combined radiocarbon dating of harp seal bones with zooarchaeological, palaeoenvironmental and stable isotope data to reconstruct the harp seal occurrence in the Baltic Sea. Our study revealed two phases of harp seal presence and verifies that the first colonization and establishment of a local breeding population occurred within the HTM. We suggest that periods with very warm summers but cold winters allowed harp seals to breed on the ice. Human pressure, salinity fluctuations with consequent changes in prey availability and competition for food resources, mainly cod, resulted in physiological stress that ultimately led to a population decline and local extirpation during the first phase. The population reappeared after a long hiatus. Final extinction of the Baltic Sea harp seal coincided with the Medieval Warm Period. Our data provide insights for the first time on the combined effects of past climatic and environmental change and human pressure on seal populations and can contribute with new knowledge on ongoing discussions concerning the impacts of such effects on current arctic seal populations.
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