Blar i forfatter "Ofstad, Siri"

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    • Arctic planktonic calcifiers in a changing ocean - A study on recent planktonic foraminifera and shelled pteropods in the Fram Strait-Barents Sea region 

      Ofstad, Siri (Doctoral thesis; Doktorgradsavhandling, 2021-12-16)
      The Arctic marine realm is being transformed due to the anthropogenically-induced climate change. In the Arctic, the effects of climate change are intensified due to polar amplification and have led to processes in the ocean such as sea-ice retreat, ocean acidification and the increased presence of boreal species referred to as ‘Atlantification’. This thesis presents rare investigations of marine ...

    • Development, productivity, and seasonality of living planktonic foraminiferal faunas and Limacina helicina in an area of intense methane seepage in the Barents Sea 

      Ofstad, Siri; Meilland, Julie; Zamelczyk, Katarzyna; Chierici, Melissa; Fransson, Agneta; Gründger, Friederike; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-09)
      Although the plankton communities in the Barents Sea have been intensely studied for decades, little is known about the living planktonic foraminiferal (LPF) and pteropod faunas, especially those found at methane seep sites. Along a repeated transect in the “crater area” (northern Barents Sea, 74.9°N, 27.7°E) in spring and summer 2016 the flux of LPF and of the pteropod species <i>Limacina helicina</i> ...

    • The FORCIS database: A global census of planktonic Foraminifera from ocean waters 

      Chaabane, Sonia; de Garidel-Thoron, Thibault; Giraud, Xavier; Schiebel, Ralf; Beaugrand, Grégory; Brummer, Geert-Jan; Casajus, Nicolas; Greco, Mattia; Grigoratou, Maria; Howa, Hélène; Ofstad, Siri; Jonkers, Lukas; Kucera, Michal; Kuroyanagi, Azumi; Meilland, Julie; Monteiro, Fanny; Mortyn, Graham; Almogi-Labin, Ahuva; Asahi, Hirofumi; Avnaim-Katav, Simona; Nassinot, Franck; Davis, Catherine V.; Field, David B.; Hernández-Almeida, Iván; Herut, Barak; Hosie, Graham; Howard, Will; Jentzen, Anna; Johns, David G.; Keigwin, Lloyd; Kitchener, John; Kohfeld, Karen E.; Lessa, Douglas V. O.; Manno, Clara; Marchant, Margarita; Ortiz, Joseph D.; Post, Alexandra; Rigual-Hernandez, Andres; Rillo, Marina C.; Robinson, Karen; Sagawa, Takuya; Sierro, Francisco; Takahashi, Kunio T.; Torfstein, Adi; Venancio, Igor; Yamasaki, Makoto; Ziveri, patrizia (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-03)
      Planktonic Foraminifera are unique paleo-environmental indicators through their excellent fossil record in ocean sediments. Their distribution and diversity are affected by different environmental factors including anthropogenically forced ocean and climate change. Until now, historical changes in their distribution have not been fully assessed at the global scale. Here we present the FORCIS ...

    • Shell density of planktonic foraminifera and pteropod species Limacina helicina in the Barents Sea: Relation to ontogeny and water chemistry 

      Ofstad, Siri; Zamelczyk, Katarzyna; Kimoto, Katsunori; Chierici, Melissa; Fransson, Agneta; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-28)
      Planktonic calcifiers, the foraminiferal species <i>Neogloboquadrina pachyderma</i> and <i>Turborotalita quinqueloba</i>, and the thecosome pteropod <i>Limacina helicina</i> from plankton tows and surface sediments from the northern Barents Sea were studied to assess how shell density varies with depth habitat and ontogenetic processes. The shells were measured using X-ray microcomputed tomography ...