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Impacts of sediment dewatering and rehydration on sediment nitrogen concentration and macrophyte growth

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Abstract:

River sediments were experimentally dewatered via exposure to air from an initial moisture content of 75% to 61% (~20% dewatered), 32% (~60% dewatered), and 4% (~95% dewatered). Sediments dewatered by 20% and 60% and rehydrated exhibited a lower exchangeable ammonium-N (NH4-N) concentration and a lower rate of nitrate/nitrite-N and NH4-N release from sediments compared with controls. In contrast, sediments dewatered by 95% and rehydrated exhibited a marked increase in exchangeable sediment NH4-N and a much higher rate of nitrate/nitrite-N (under oxic conditions) and NH4-N (under oxic and anoxic conditions) release from sediments. Sediment dewatered by 60% and 95% and rehydrated lost total N (18%), suggesting denitrification. Growth of Potamogeton pectinatus responded to changes in the exchangeable sediment NH4-N concentration; it was lower on partially dewatered and rehydrated sediments that exhibited lower exchangeable sediment NH4-N and elevated on sediment that was dewatered by 95%. Our results suggest that sediment N may be altered via sediment dewatering and rehydration to affect macrophyte growth.

Nous avons déshydraté expérimentalement par exposition à l'air des sédiments de rivière dont le contenu initial d'humidité était de 75 % à 61 % (~20 % de déshydratation), 32 % (~60 % de déshydratation et 4 % (~95 % de déshydratation). Les sédiments déshydratés de 20 % et de 60 % et ensuite réhydratés possèdent une concentration réduite d'azote-ammonium (NH4-N) échangeable et un taux de libération réduit d'azote-nitrate/nitrite et de NH4-N par comparaison aux sédiments témoins. En revanche, les sédiments déshydratés de 95 % et ensuite réhydratés affichent un accroissement marqué de NH4-N échangeable dans les sédiments et des taux beaucoup plus élevés de libération d'azote- nitrate/nitrite (en conditions oxiques) et de NH4-N (en conditions oxiques et anoxiques). Les sédiments déshydratés de 60 % et de 95 % et ensuite réhydratés perdent 18 % de leur azote total, ce qui fait croire à une dénitrification. La croissance de Potamogeton pectinatus réagit aux changements de concentrations du NH4-N échangeable dans les sédiments; elle est plus faible dans les sédiments déshydratés puis réhydratés qui possèdent des concentrations plus basses de NH4-N échangeable et plus élevée dans les sédiments déshydratés à 95 %. Nos résultats indiquent que l'azote des sédiments peut être altéré par la déshydratation et la réhydratation de manière à affecter la croissance des macrophytes.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: April 1, 2004

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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