Role of tidal pumping on nutrient cycling in a temperate lagoon (Arcachon Bay, France)

Type Article
Date 2008-02
Language English
Author(s) Deborde JORCID1, Anschutz P1, Auby IsabelleORCID2, Gle C1, Commarieu M1, Maurer Daniele2, Lecroart P1, Abril G1
Affiliation(s) 1 : Univ Bordeaux 1, CNRS, UMR 5805, EPOC, F-33405 Talence, France.
2 : IFREMER, DEL AR, F-33120 Arcachon, France.
Source Marine Chemistry (0304-4203) (Elsevier), 2008-02 , Vol. 109 , N. 1-2 , P. 98-114
DOI 10.1016/j.marchem.2007.12.007
WOS© Times Cited 60
Keyword(s) Arcachon Bay, Pore waters seeping, Nitrogen, Phosphorus, Organic matter mineralization, Tidal creek water, Tidal pump
Abstract The hypothesis of nutrient-rich pore-waters seeping at low tide through sediments to channel waters, which drain tidal flats during ebb, was evaluated in the Arcachon lagoon. The back of the bay is affected by freshwater inputs and underground freshwater discharges. The upper part of tidal flat consists of permeable sandy sediments, which are covered by a muddy sediment layer on the lower part. Permeable sediments outcrop in the bed of channel web. Surface water chemistry and early diagenesis processes in sediment were estimated by collecting channel web waters and cores on a tidal flat and in channels at different seasons and time scales. Waters from tidal creeks are under-oxygenated, and enriched in reduced solutes. Muddy sediments showed evidences of strong organic matter mineralization and bioturbation. Underlying permeable sandy sediments revealed as well evidences of an enrichment of inorganic nutrients, and dilution with fresh continental groundwater. During ebb, tidal creek waters stem from mudflats by seeping of anoxic pore-waters, and from permeable sediments by advection of reduced waters. A rough estimation shows that the yearly contribution of this tidal pump of pore-waters for dissolved inorganic phosphorus (DIP) and ammonia inputs is of the same order of magnitude than river inputs for the studied part of the bay. Extrapolated to the whole Arcachon lagoon, pore-water discharge at low tide supplies to water column at least 556 kmol yr(-1) and 18300 kmol yr(-1) of DIP and NH4+, respectively. Tidal drainage at low tide represents therefore a minimal contribution of recycled nutrient of 55% for DIP and 15% for dissolved inorganic nitrogen to the lagoon. (c) 2008 Elsevier B.V. All rights reserved.
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