MEPS 392:43-55 (2009)  -  doi:10.3354/meps08179

Oxidation of surface sediment: effects of disturbance depth and seawater flow speed

Kay Vopel1,2,*, Conrad A. Pilditch3, Peter Wilson1,2, Michael J. Ellwood4

1Auckland University of Technology, Earth and Oceanic Sciences Research Institute, Mail No C43, Private Bag 92006, Auckland, New Zealand
2National Institute of Water and Atmospheric Research, PO Box 11–115, Hamilton, New Zealand
3University of Waikato, Department of Biological Sciences, Private Bag 3105, Hamilton, New Zealand
4Department of Earth and Marine Sciences, Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

ABSTRACT: Periodic disturbance of surface sediment is a natural feature of marine environments. Following exposure to oxygenated seawater, the disturbed sediment oxidises leading to the recovery of its surface chemistry. Despite its importance for the ecology of the sediment–water interface, the dynamics of this recovery is not well known. We studied the effects of disturbance depth and seawater flow speed on the oxidation of estuarine cohesive sediment in a laboratory flume with microelectrodes. We removed surface sediment to 2 depths (5 and 50 mm) and then observed changes in sediment O2 distribution and consumption over 1 h under conditions of slow and fast flow (3.5 and 7.5 cm s–1). Measurements were repeated 1 d later. The consumption of O2 in the treated sediments reached a ‘quasi stable state’ within 7 h (50 mm depth) and 16 h (5 mm depth) characterised by very slow changes due to slow oxidation of reduced solids. Faster flow increased the rate at which sediment from 50 mm depth oxidised but not that of the sediment from 5 mm depth. After 20 to 24 h, sediments disturbed to 50 and 5 mm depths still differed in O2 distribution and consumption, both from each other and from the pre-treatment sediment. Differences in the response of pore water O2 distribution to an abrupt increase in flow speed (3.5 to 7.5 cm s–1) were also still evident at this time. Our measurements confirmed the results of previous theoretical analyses in that they indicate that the duration of the recovery of the surface sediment chemistry from disturbance and the chemical properties of the recovering sediment are controlled by the kinetics of solute and solid oxidation. Oxidation of reduced solids in disturbed sediment can result in a characteristic chemical signature at the sediment surface that lasts in the order of at least days.

KEY WORDS: Cohesive sediment · Oxygen flux · Sediment respiration · Recovery

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Cite this article as: Vopel K, Pilditch CA, Wilson P, Ellwood MJ (2009) Oxidation of surface sediment: effects of disturbance depth and seawater flow speed. Mar Ecol Prog Ser 392:43-55

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