Oxygen as a control on seafloor biological communities and their roles in sedimentary carbon cycling

Clare Woulds, G Cowie, L A Levin, Johan H. Andersson, JJ Middelburg, Sandra Vandewiele, Peter Lamont, Kate Larkin, Andrew Gooday, Stefanie Schumacher, Christine Whitcraft, Rachel Jeffreys, Matthew Schwartz

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Abstract

C-13 tracer experiments were conducted at sites spanning the steep oxygen, organic matter, and biological community gradients across the Arabian Sea oxygen minimum zone, in order to quantify the role that benthic fauna play in the short-term processing of organic matter (OM) and to determine how this varies among different environments. Metazoan macrofauna and macrofauna-sized foraminiferans took up as much as 56 +/- 13 mg of added C m(-2) (685 mg C m(-2) added) over 2-5 d, and at some sites this uptake was similar in magnitude to bacterial uptake and/or total respiration. Bottom-water dissolved oxygen concentrations exerted a strong control over metazoan macrofaunal OM processing. At oxygen concentrations > 7 mu mol L-1 (0.16 ml L-1), metazoan macrofauna were able to take advantage of abundant OM and to dominate OM uptake, while OM processing at O-2 concentrations of 5.0 mu mol L-1 (0.11 ml L-1) was dominated instead by (macrofaunal) foraminiferans. This led us to propose the hypothesis that oxygen controls the relative dominance of metazoan macrofauna and foraminifera in a threshold manner, with the threshold lying between 5 and 7 mu mol L-1 (0.11 to 0.16 ml L-1). Large metazoan macrofaunal biomass and high natural concentrations of OM were also associated with rapid processing of fresh OM by the benthic community. Where they were present, the polychaete Linopherus sp. and the calcareous foraminiferan Uvigerina ex gr. semiornata, dominated the uptake of OM above and below, respectively, the proposed threshold concentrations of bottom-water oxygen.
Original languageEnglish
Pages (from-to)1698-1709
Number of pages12
JournalLIMNOL OCEANOGR
Volume52
Issue number4
Publication statusPublished - 2007

Keywords

  • RAPID RESPONSE
  • CONTINENTAL MARGINS
  • BENTHIC FORAMINIFERA
  • ORGANIC-CARBON
  • SLOPE SEDIMENTS
  • IN-SITU
  • DEEP-SEA
  • ARABIAN SEA
  • Limnology
  • DEFICIENT ZONE
  • Oceanography
  • PHYTODETRITUS DEPOSITION

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    Woulds, C., Cowie, G., Levin, L. A., Andersson, J. H., Middelburg, JJ., Vandewiele, S., Lamont, P., Larkin, K., Gooday, A., Schumacher, S., Whitcraft, C., Jeffreys, R., & Schwartz, M. (2007). Oxygen as a control on seafloor biological communities and their roles in sedimentary carbon cycling. LIMNOL OCEANOGR, 52(4), 1698-1709. http://www.aslo.org/lo/toc/vol_52/issue_4/1698.pdf