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Volume 12, issue 5
Biogeosciences, 12, 1537–1559, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Low oxygen environments in marine, fresh and estuarine...

Biogeosciences, 12, 1537–1559, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Mar 2015

Research article | 11 Mar 2015

Organic carbon production, mineralisation and preservation on the Peruvian margin

A. W. Dale1, S. Sommer1, U. Lomnitz1, I. Montes2, T. Treude1,3, V. Liebetrau1, J. Gier1, C. Hensen1, M. Dengler1, K. Stolpovsky1, L. D. Bryant1, and K. Wallmann1 A. W. Dale et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 2Instituto Geofísico del Perú (IGP), Lima, Peru
  • 3Present address: University of California, Los Angeles (UCLA), USA

Abstract. Carbon cycling in Peruvian margin sediments (11 and 12° S) was examined at 16 stations, from 74 m water depth on the middle shelf down to 1024 m, using a combination of in situ flux measurements, sedimentary geochemistry and modelling. Bottom water oxygen was below detection limit down to ca. 400 m and increased to 53 μM at the deepest station. Sediment accumulation rates decreased sharply seaward of the middle shelf and subsequently increased at the deep stations. The organic carbon burial efficiency (CBE) was unusually low on the middle shelf (<20%) when compared to an existing global database, for reasons which may be linked to episodic ventilation of the bottom waters by oceanographic anomalies. Deposition of reworked, degraded material originating from sites higher up on the slope is proposed to explain unusually high sedimentation rates and CBE (>60%) at the deep oxygenated sites. In line with other studies, CBE was elevated under oxygen-deficient waters in the mid-water oxygen minimum zone. Organic carbon rain rates calculated from the benthic fluxes alluded to efficient mineralisation of organic matter in the water column compared to other oxygen-deficient environments. The observations at the Peruvian margin suggest that a lack of oxygen does not greatly affect the degradation of organic matter in the water column but promotes the preservation of organic matter in sediments.

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