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Deep-sea benthic foraminifera, carbonate dissolution and species diversity in Hardangerfjord, Norway: An initial assessment

Deep-sea benthic foraminifera, carbonate dissolution and species diversity in Hardangerfjord, Norway: An initial assessment
Deep-sea benthic foraminifera, carbonate dissolution and species diversity in Hardangerfjord, Norway: An initial assessment
This is the first record of live (stained) deep-sea benthic foraminifera in the 850 m deep silled Hardangerfjord, the second deepest fjord in Western Norway. Estimates of organic carbon flux (not, vert, similar2.5 g Cm?2 y?1) show that the fjord-values are comparable to similar depths on the continental slope. Accordingly, although these first samples only provide relative abundance data, the low proportion of live to dead individuals in the top cm of the sediment suggests a low foraminifera biomass. Another similarity with the deep sea is that the abiotic environment of the deep basins is stable even though the deepest basins are isolated from the open deep sea by the continental shelf and sills in the outer parts of the fjord suggesting that the deep-sea species are introduced as propagules during deep-water renewals. There is evidence of an increase in dissolution of fragile calcareous tests (e.g., Nonionella iridea) especially in the innermost part of Hardangerfjord since the 1960s and this has led to a relative increase in dead agglutinated assemblages. The presence of larger forms with tests >1 mm provides substrata for the attachment of smaller forms and therefore an increase in species diversity. Indeed, the diversity is comparable both to that of the open deep sea and that of reported macrofauna from the same sites, reflecting similar ecological status. Holtedahl (1965) suggested that there may be some down-slope transport of sediment into the deep basins with the deposition of turbidites. Despite some evidence of transport, no major recent disturbance due to turbidite deposition seems to have occurred and hence Hardangerfjord presents a unique environment with elements of deep-sea faunas in a land-locked setting.
Bathyal silled fjord, foraminiferal dispersal, turbidites, taphonomy, carbonate dissolution, biodiversity
0272-7714
90-102
Alve, Elisabeth
aae74d58-6787-4e19-9b74-4eaf4068b27f
Murray, John W.
3985aa41-1e0e-4504-ab90-e31a00c33c38
Skei, Jens
745e825a-147a-43e9-8b6b-bd6a8ee669e0
Alve, Elisabeth
aae74d58-6787-4e19-9b74-4eaf4068b27f
Murray, John W.
3985aa41-1e0e-4504-ab90-e31a00c33c38
Skei, Jens
745e825a-147a-43e9-8b6b-bd6a8ee669e0

Alve, Elisabeth, Murray, John W. and Skei, Jens (2011) Deep-sea benthic foraminifera, carbonate dissolution and species diversity in Hardangerfjord, Norway: An initial assessment. Estuarine, Coastal and Shelf Science, 92 (1), 90-102. (doi:10.1016/j.ecss.2010.12.018).

Record type: Article

Abstract

This is the first record of live (stained) deep-sea benthic foraminifera in the 850 m deep silled Hardangerfjord, the second deepest fjord in Western Norway. Estimates of organic carbon flux (not, vert, similar2.5 g Cm?2 y?1) show that the fjord-values are comparable to similar depths on the continental slope. Accordingly, although these first samples only provide relative abundance data, the low proportion of live to dead individuals in the top cm of the sediment suggests a low foraminifera biomass. Another similarity with the deep sea is that the abiotic environment of the deep basins is stable even though the deepest basins are isolated from the open deep sea by the continental shelf and sills in the outer parts of the fjord suggesting that the deep-sea species are introduced as propagules during deep-water renewals. There is evidence of an increase in dissolution of fragile calcareous tests (e.g., Nonionella iridea) especially in the innermost part of Hardangerfjord since the 1960s and this has led to a relative increase in dead agglutinated assemblages. The presence of larger forms with tests >1 mm provides substrata for the attachment of smaller forms and therefore an increase in species diversity. Indeed, the diversity is comparable both to that of the open deep sea and that of reported macrofauna from the same sites, reflecting similar ecological status. Holtedahl (1965) suggested that there may be some down-slope transport of sediment into the deep basins with the deposition of turbidites. Despite some evidence of transport, no major recent disturbance due to turbidite deposition seems to have occurred and hence Hardangerfjord presents a unique environment with elements of deep-sea faunas in a land-locked setting.

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More information

Published date: 20 March 2011
Keywords: Bathyal silled fjord, foraminiferal dispersal, turbidites, taphonomy, carbonate dissolution, biodiversity

Identifiers

Local EPrints ID: 180039
URI: https://eprints.soton.ac.uk/id/eprint/180039
ISSN: 0272-7714
PURE UUID: 61ce77a2-bdbd-4983-8d81-64bc2e685123

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Date deposited: 05 Apr 2011 10:15
Last modified: 16 Jul 2019 23:43

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