The structure of benthic environments and the paleochemical record of foraminifera

• Published in: Deep-sea research. Part I, Oceanographic research papers Vol. 58; no. 5; pp. 535 - 545
• Main Authors: Loubere, Paul, Jacobsen, Brittani, Klitgaard Kristensen, Dorthe, Husum, Katrine, Jernas, Patrycja, Richaud, Mathieu
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.05.2011; Elsevier; Pergamon Press Inc
• Subjects: Benthic foraminiferal ecology; Carbon; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; Habitats; Invertebrate paleontology; Isotope and element geochemical proxies; Isotope geochemistry; Isotope geochemistry. Geochronology; Marine; Marine biology; Marine pore-water geochemistry; Microhabitats; Mineralogy; Nonnative species; Oceanography; Paleoceanographic proxies; Paleontology; Proxy client servers; Sediments; Shells; Silicates; Tracers; Water geochemistry; polar regions; Svalbard; North Atlantic; Arctic region; Atlantic Ocean; Marine pore-water geochemistry; Isotope and element geochemical proxies; Paleoceanographic proxies; Benthic foraminiferal ecology; stable isotopes; C-13/C-12; paleo-oceanography; fjords; foraminifera; benthic environment; pore water; benthonic taxa; Invertebrata; Protista; biostratigraphy; continental margin; oxygen; organic carbon
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2011.02.011

Benthic foraminiferal shell geochemistry has been extensively used to develop paleoceanographic tracers. Many of these proxies are sensitive to the geochemical conditions of the microhabitats selected by particular foraminiferal species. Understanding these microhabitats, then, is essential for proper interpretation of the proxies. A simple, broadly accepted, view is that foraminiferal species’ habitats are vertically stratified in the sediments due to general pore-water chemical gradients, which develop in response to the seabed organic carbon flux. Species are categorized into epifaunal, shallow infaunal and deep infaunal habitats, and are supposed to acquire the geochemical characteristics of these. However, this view is at odds with species’ distributional data and foraminiferal geochemical properties. We present an alternate model in which foraminifera select for habitats within the bio-irrigation system of the sediments created by the activities of macro-/meio-fauna. Our distributional and geochemical data indicate that foraminiferal species seek particular biotic associations and geochemical conditions within the complex bio-architecture of the sediments and are not tied to particular sediment depths, or the general pore-water chemistry of their apparent habitation zone. Instead, foraminifera inhabit micro-environments with steep oxic to anoxic gradients. This might account for disparities among geochemical tracers. ►living benthic foraminiferal populations inhabit primarily seabed biostructures ► the geochemistry of pore water within and outside of biostructures differs ► this difference influences the geochemistry of isotopes and elements in foraminiferal calcite ► the biostructure habitats of benthic foraminifera may explain conflicts among geochemical proxies