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Impact of interrelated and interdependent ecological controls on benthic foraminifera: an example from the Gulf of Guinea

Impact of interrelated and interdependent ecological controls on benthic foraminifera: an example from the Gulf of Guinea
Impact of interrelated and interdependent ecological controls on benthic foraminifera: an example from the Gulf of Guinea
Living and dead benthic foraminiferal assemblages from two size fractions, 63–250 ?m and >250 ?m, were studied at 128 stations from the shelves down to abyssal plains of the Gulf of Guinea in the eastern equatorial Atlantic. The sample size ranged between 300 and 400 cm2 of the sediment/water interface, with a penetration depth of 1 cm. Environmental parameters were quantified for sediment composition, food webs, bottom-water oxygen concentrations, and benthic oxygen respiration. Seven major station groupings (named G1–G7) are subdivided by factor analysis. The three most abundant species therein are discussed with respect to their ecological requirements, for both size classes and for living and dead counts. For 49 living species, the range of environmental gradients is established, and for five species live observations are reported. Five station groupings can be attributed toward stepwise ranges scaled by bathymetry and flux rates of organic carbon (G4, 27–75 m; G5, 68–269 m; G6, 250–740 m; G2, 674–2007 m; G1, 1475–4970 m). Two geographically restricted station groupings locally interfinger with other groupings in the upper bathyal and abyssal water depths (G7, 82–451 m; G3, 1002–4658 m). G7 shows lowered oxygen concentrations and benthic oxygen respirations, whereas hemipelagic sediments are typical of G3. The interfingering of G7 and G3, however, is not purely a result of the increasing number of species most perfectly adapted to these environments but rather that these groupings are structured by the decrease of species with lower tolerance towards environmental perturbation. In fact, the more common species have an environmental range much broader than the environmental frame of the groupings they dominate. This observation holds for all size classes and for live and dead counts. We conclude that species-specific preferences and thresholds provide a more valuable and more consistent tool in environmental research than the environmental ranges observed for assemblages.
eastern equatorial Atlantic, shelf, slope, deep sea, environment, neontology
0031-0182
213-238
Altenbach, A.V.
dbf0eebd-5200-4914-b2a5-d9831e99e611
Lutze, G.
7e543c4b-1aec-43cb-9a10-50329d179e1a
Schiebel, R.
e3ee9c3f-ae96-4523-8ec2-2ed7acdfb83a
Schonfeld, J.
4de69a9a-517e-48cf-9441-4882d060971f
Altenbach, A.V.
dbf0eebd-5200-4914-b2a5-d9831e99e611
Lutze, G.
7e543c4b-1aec-43cb-9a10-50329d179e1a
Schiebel, R.
e3ee9c3f-ae96-4523-8ec2-2ed7acdfb83a
Schonfeld, J.
4de69a9a-517e-48cf-9441-4882d060971f

Altenbach, A.V., Lutze, G., Schiebel, R. and Schonfeld, J. (2003) Impact of interrelated and interdependent ecological controls on benthic foraminifera: an example from the Gulf of Guinea. Palaeogeography, Palaeoclimatology, Palaeoecology, 197 (3-4), 213-238. (doi:10.1016/S0031-0182(03)00463-2).

Record type: Article

Abstract

Living and dead benthic foraminiferal assemblages from two size fractions, 63–250 ?m and >250 ?m, were studied at 128 stations from the shelves down to abyssal plains of the Gulf of Guinea in the eastern equatorial Atlantic. The sample size ranged between 300 and 400 cm2 of the sediment/water interface, with a penetration depth of 1 cm. Environmental parameters were quantified for sediment composition, food webs, bottom-water oxygen concentrations, and benthic oxygen respiration. Seven major station groupings (named G1–G7) are subdivided by factor analysis. The three most abundant species therein are discussed with respect to their ecological requirements, for both size classes and for living and dead counts. For 49 living species, the range of environmental gradients is established, and for five species live observations are reported. Five station groupings can be attributed toward stepwise ranges scaled by bathymetry and flux rates of organic carbon (G4, 27–75 m; G5, 68–269 m; G6, 250–740 m; G2, 674–2007 m; G1, 1475–4970 m). Two geographically restricted station groupings locally interfinger with other groupings in the upper bathyal and abyssal water depths (G7, 82–451 m; G3, 1002–4658 m). G7 shows lowered oxygen concentrations and benthic oxygen respirations, whereas hemipelagic sediments are typical of G3. The interfingering of G7 and G3, however, is not purely a result of the increasing number of species most perfectly adapted to these environments but rather that these groupings are structured by the decrease of species with lower tolerance towards environmental perturbation. In fact, the more common species have an environmental range much broader than the environmental frame of the groupings they dominate. This observation holds for all size classes and for live and dead counts. We conclude that species-specific preferences and thresholds provide a more valuable and more consistent tool in environmental research than the environmental ranges observed for assemblages.

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Published date: 2003
Keywords: eastern equatorial Atlantic, shelf, slope, deep sea, environment, neontology

Identifiers

Local EPrints ID: 35593
URI: http://eprints.soton.ac.uk/id/eprint/35593
ISSN: 0031-0182
PURE UUID: 77671b6e-8e56-49dd-8664-7e0a58c457ef

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Date deposited: 22 May 2006
Last modified: 15 Mar 2024 07:53

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Contributors

Author: A.V. Altenbach
Author: G. Lutze
Author: R. Schiebel
Author: J. Schonfeld

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