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Drastic changes in deep‐sea sediment porewater composition induced by episodic input of organic matter
Author(s) -
Gehlen Marion,
Rabouille Christophe,
Ezat Ullah,
GuidiGuilvard Laurence D.
Publication year - 1997
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1997.42.5.0980
Subject(s) - organic matter , sediment–water interface , sediment , total organic carbon , denitrification , deposition (geology) , pelagic sediment , pelagic zone , nitrification , oceanography , bottom water , mediterranean climate , environmental science , environmental chemistry , geology , chemistry , nitrogen , ecology , geomorphology , biology , organic chemistry
We report the first seasonal time‐series observations of porewater composition obtained for deep‐sea sediments. We observed considerable temporal variability of O 2 , NO 3 − , and Mn 2+ profiles at the French JGOFS site DYFAMED (western Mediterranean) in response to a pulsed input of organic matter. A delivery of reactive organic matter representing only 1% of the average organic C content of surface sediments (0.6% wt/wt) was required in order to fuel the observed changes in porewater composition. The perturbation resulted in dramatic changes in integrated reaction rates and sediment‐water fluxes. O 2 uptake rates increased from 1.26 to 1.82 mmol m −2 d −1 , while nitrification rates rose from 0.13 to 0.18 mmol m −2 d −1 . These changes were paralleled by a decrease in NO 3 − effluxes across the sediment‐water interface from 0.07 to 0.01 mmol m −2 d and a concomitant rise of denitrification rates from 0.06 to 0.17 mmol m −2 d −1 . Porewater profiles responded rapidly to the sediment pulse deposition, returning to their steady‐state values within a few months. The main driving force appeared not to be the seasonal variability of pelagic production but rather the downslope transport of resuspended upper‐shelf sediments.