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Helena Filipsson, foto Erik Thor

Helena Filipsson

Professor

Helena Filipsson, foto Erik Thor

Stable carbon isotope evidence of the establishment of a new, opportunistic foraminiferal fauna in a Swedish Skagerrak fjord basin, in 1979/1980

Författare

  • Kjell Nordberg
  • Helena Filipsson
  • Pernilla Linné
  • Mikael Gustafsson

Summary, in English

Significant faunal changes reported fromrecent, coastal environments,which are not directly influenced by urban and industrial impact, are rarely seen. In Gullmar Fjord on the Swedish west coast, a significant foraminiferal fauna change occurred in connectionwith severe low-oxygen conditions that evolved in thewinter of 1979/1980. A foraminiferal fauna marked by common Skagerrak–Kattegat species, which had previously characterised the deep fjord basin, was replaced by the opportunistic, low-oxygen tolerant species Stainforthia fusiformis (Williamsson).

To study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself, S. fusiformis, both on specimens from sediment cores representing approximately the last 85 years

and on living (stained) individuals taken from a transect across the deep fjord basin. Our purpose was to detail how and why S. fusiformis, came to dominate the fauna. The oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c. 85 years, while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979/1980. The combined results from both the cores and the surface sediments suggest that S. fusiformis did not inhabit the deep basin until 1980. Before then, almost all specimens of S. fusiformis were small sized and their carbon isotope values suggest they were re-deposited shallow-water specimens that had been transported down to the central, deep basin as part of a suspension load. After a major faunal extinction in 1979–1980, S.fusiformis of all sizes suddenly appeared in large numbers and their carbon

isotopic values were similar to the signal from registered in the recent, living fauna within the deep basin. This suggests that the opportunistic S. fusiformis established itself in the deep basin as a consequence of the severe low-oxygen event and the faunal crash of the previously dominating Skagerrak–Kattegat fauna.

Avdelning/ar

  • Kvartärgeologi

Publiceringsår

2009

Språk

Engelska

Sidor

117-128

Publikation/Tidskrift/Serie

Marine Micropaleontology

Volym

73

Issue

1-2

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Geology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1872-6186