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- Polovodova Asteman, Irina, 1980, et al.
(författare)
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Distribution of the putative invasive species Nonionella sp. T1 in the Gullmar Fjord – What is its potential contribution to biogeochemical cycles?
- 2023
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Ingår i: International Congress FORAMS2023, Perugia, Italy 25-30th June 2023.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Benthic foraminifera, both fossil and living, have been extensively studied in the seasonally hypoxic Gullmar Fjord (Sweden) for decades to decipher hydrographic changes and ecological status. In 2011, a non-indigenous species named Nonionella sp. T1 was discovered in the fjord for the first time. Here, we aim at evaluating its putative invasive behavior and life strategies by combining assemblage analyses of living foraminifera along a fjord transect of surface sediment (0-3 cm) together with four longer sediment cores (0-5 cm) from two stations at 51 m and 117 m water depth. Our results showed that Nonionella sp. T1 collected in the surface sediment in September 2021 and 2022, was present in almost all the transect samples. This species dominated the living foraminiferal assemblages with an abundance between 15 and 72 %, at seven of the eight sites visited. The highest relative and absolute abundances were noted between 39 and 78 m water depth, proximal to the fjord mouth, with a reduced presence towards the deepest station and the fjord head. However, Nonionella sp. T1 was completely absent in the sandy sediments at the shallowest station (1 m water depth). Sediment cores collected in November 2017 and May 2022 revealed that Nonionella sp. T1 exhibited higher abundance at 51 m water depth compared to 117 m. In a previous study, higher densities were observed at the station 51 m below the oxygenated sediment zone (< 2 mm depth), where high nitrate concentrations in pore waters were measured (2017 data). The authors demonstrated that Nonionella sp. T1 respires nitrate and the pool of specimens denitrifies up to 50 % – 100 % of the nitrate in sediment porewaters, revealing its non-negligible contribution to benthic denitrification. The 10-fold higher abundance of Nonionella sp. T1 recorded in 2022 (compared to 2017) supports previous hypotheses about their invasive character and alerts about their important role in the nitrogen cycle of the Gullmar Fjord. The results of this study highlight the need for continued monitoring of this invasive species, its spreading dynamics and ecological/biogeochemical impacts.
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- Polovodova Asteman, Irina, 1980, et al.
(författare)
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Spreading of an alien benthic foraminifer in the North Sea: a reason to be worried?
- 2023
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Ingår i: International Congress FORAMS2023, Perugia, Italy, 25-30th June. - Perugia, Italy : Micropress Europe & The Grzybowski Foundation.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the Skagerrak-Kattegat (eastern North Sea), the alien benthic foraminifer Nonionella sp. T1 (previously referred to as “Nonionella stella”) was reported for the first time in 2011 and 2012 in the Swedish and southern Norwegian fjords, respectively. Based on dated sediment cores its first occurrence can be traced back to the 1980s in the Gullmar Fjord, to the 2000s in the Öresund and to 2010 in the Oslofjord. Since then, Nonionella sp T1 has spread all over the Kattegat and coastal Skagerrak, according to sampling campaigns performed between 2016 and 2022. The species is now highly abundant in the entire Kattegat, including the Öresund, as well as in fjord mouths of the seasonally hypoxic Gullmar Fjord, the oxic Hakefjord and the long-term polluted Idefjord as demonstrated by molecular and morphospecies data. At the same time, Nonionella sp T1 is rare to absent in the Baltic Sea, Skagerrak deep basin and in deep fjords of western and northern Norway. This study shows some preliminary results on the species’ present distribution in the study area and raises questions about the driving factors and potential effects on the local biodiversity.
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- Polovodova, Irina, 1980, et al.
(författare)
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Detailing the Little Ice Age on the Swedish west coast: a multi-proxy study of a sediment record from Gullmar Fjord
- 2014
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Ingår i: Marchant, M . & Hromic, T. (eds . ) 201 4 . Internation al Symposium on Foraminifera Forams 2014, Chile, 19 – 24 January 2014 , Abstract Volume . Grzybowski Foundation Special Publication, 20 , 124 pp.. - 9788388927355 ; , s. 38-39
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Gullmar Fjord, on the west coast of Sweden, represents a high-resolution environmental archive due to high sedimentation rates, low bioturbation and negligible tidal activity. In this study we attempt to detail the climatic and environmental changes in NE Europe during the last millennium by using a ca. 8-m long well dated sediment record from the deep fjord basin. According to the 14C-datings, the record includes the period of the late Holocene characterised by anomalously cold summers and well known as the Little Ice Age (LIA). Using a high-resolution stratigraphy of benthic foraminifera and dinoflagellate cysts along with lithology, bulk sediment geochemistry and foraminiferal δ13C we identify the timing of the cold period, reconstruct its various phases, and discuss the land-sea interactions occurring in the study area during that time. The onset of the LIA is indicated at ~1350 A.D by an increase in abundances of cold-water foraminifer Adercotryma glomerata and the cryophilic dinoflagellate cyst Islandinium cf. cezare. The first phase of the LIA was characterised by a stormy climate and higher productivity, as suggested by a foraminiferal assemblage of Nonionella iridea and Cassidulina laevigata. The hypothesis of higher productivity is supported by the isotopic and the dinoflagellate cyst records, which show a shift towards more negative δ13C values, and a marked increase in the microreticulate cysts of Gymnodinium nolleri at the onset of the LIA. The dinoflagellate species G. nolleri becomes relict towards the LIA termination and could be also associated with lower surface water temperatures at that time. It is likely that due to land use changes in the second part of the LIA there was an increased input of terrestrial organic matter to the fjord, which is indicated by lighter δ13C values and an increase of detritivorous and omnivorous foraminiferal species such as Textularia earlandi and Eggerelloides scaber. The climate deterioration during the climax of the LIA (1675-1704 A.D.) may have driven a decline in primary productivity, as suggested by the increase of agglutinated foraminiferal species, the presence of Hyalinea balthica, and a decline of N. iridea during that time.
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- Polovodova, Irina, 1980, et al.
(författare)
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High resolution foraminiferal stratigraphy and climatic variations over the last ca. 2500 years: Evidence from Gullmar Fjord and Skagerrak-Kattegat area
- 2010
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Ingår i: International Symposium on Foramininfera Forams 2010, September 5-10th, 2010, University of Bonn, Germany. ; , s. 164-164
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sediment cores from Gullmar Fjord (Swedish west coast) and the Skagerrak-Kattegat area were analysed for benthic foraminifera and stable δ13C isotope data. We obtained high-resolution records encompassing climatic variations over the last 2,500 years. In Gullmar Fjord, the δ13C curve shows distinctly negative values during Roman, Medieval, and Recent warm periods, but also during the Little Ice Age. Benthic foraminifera show profound changes in the record characterized by the decline of Nonionella iridea, Adercotryma glomerata and Cassidulina laevigata and the establishment of Hyalinea balthica and Stainforthia fusiformis. Roman and Medieval warm periods are characterized by similar foraminiferal assemblages, whereas Little Ice Age and Recent warming show significantly different faunal composition. The data are compared to records from Skagerrak and Kattegat in order to see if there are regional signals for these climatic events.
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