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Response of deep-water agglutinated foraminifera to dysoxic conditions in the California Borderland basins

Kaminski, M.A.; Boersma, E.; Tyszka, J.; Holbourn, A.E.L.; (1995) Response of deep-water agglutinated foraminifera to dysoxic conditions in the California Borderland basins. In: Kaminski, M.A. and Geroch, S. and Gasinski, M.A., (eds.) Proceedings of the Fourth International Workshop on Agglutinated Foraminifera. (pp. pp. 131-140). Grzybowski Foundation: London, UK. Green open access

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Abstract

Analysis of agglutinated benthic foraminifera from surface samples collected in the San Pedro and Santa Catalina Basins reveals a predictable relationship between the proportions of morphogroups with decreasing bottom water oxygen levels and with the TOC content of the surficial sediment. Living (Rose Bengal stained) foraminiferal faunas from dysaerobic environments display low diversity and high dominance, suggesting stressed conditions. There is an inverse relationship between oxygen and the relative abundance of deep infaunal morphogroups. Samples collected from shallow stations above the oxygen minimum zone are comprised of epifaunal and shallow infaunal morphotypes. At intermediate depths (~500 m), there is a peak in the abundance of suspension-feeding and "climbing" forms (watchglass-shaped trochamminids attached to Rhabdammina). Specimens from intermediate stations display the largest overall size. Deeper in the San Pedro Basin the living fauna is dominated by a small, flattened, tapered, species that is interpreted as having a deep infaunal microhabitat. In the dysaerobic environments off California the greatest degree of faunal change occurs when bottom water dissolved oxygen values drop from 0.5 ml/l to 0.2 ml/l. The effect of TOC content on the benthic fauna is demonstrated at two stations from the same depth in the San Pedro Basin. The station with the higher TOC content (4.2% vs. 2.9%) contains greater proportions of the small, deep infaunal morphotype. These faunal changes may be attributed to differences in the depth of the oxygenated zone within the sediment surface layer. Agglutinated faunas from areas that experience seasonal anoxia are comprised of a large proportion of opportunistic forms such as Reophax and Psammosphaera. These are the same taxa that colonised abiotic sediment trays in a recolonisation experiment in the Panama Basin. This study further demonstrates that agglutinated foraminiferal morphotypes respond in a similar manner to calcareous benthic foraminifera in dysaerobic environments.

Type: Proceedings paper
Title: Response of deep-water agglutinated foraminifera to dysoxic conditions in the California Borderland basins
ISBN-13: 9788390116426
Open access status: An open access version is available from UCL Discovery
Publisher version: http://www.ucl.ac.uk/es/Grzybowski/public.htm
Language: English
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/18878
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