Rev. biol. mar. oceanogr. 47(2): 167-175 



Nitrate reduction activity determined with a continuous flow-through system in sediments from a subantarctic coastal environment

Américo I. Torres1, Mónica N. Gil1 & José Luis Esteves1

1Laboratorio de Oceanografía Química y Contaminación de Aguas, Centro Nacional Patagónico, (CONICET), Boulevard Brown 2915, (9120) Puerto Madryn, Chubut, Argentina

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Sedimentation and accumulation of autochthonous and allochthonous organic detritus in marine sediments stimulate microbial activity, consume dissolved oxygen and decrease redox potential. In anaerobic conditions, other electron acceptors are utilized in organic matter oxidation process. Nitrate reduction is an important pathway which is related with nitrogen cycling and oxidation. The purpose of this study was to assess the nitrate reduction activity in sediments of Encerrada Bay, which is under a strong anthropogenic influence from Ushuaia city. Sediment samples were taken in September 2007 with a Van-Veen dredge and stored in darkness. Nitrate reduction activity was estimated in vitro using continuous flow-through system. Nitrate uptake rate followed a Michaelis-Menten kinetic where Km and Vmax values were equal to 1028 mM and 2.7 mmol g-1 h-1, respectively. We concluded that nitrate is used principally as terminal electron acceptor during the oxidation of organic compounds in sediment of Encerrada Bay.

Key words: Nitrate, ammonium, reactor, denitrification, Argentinean Patagonia