Biosensor for laboratory and lander-based analysis of benthic nitrate plus nitrite distribution in marine environments

Niels Peter Revsbech, Ronnie Nøhr Glud

Limnol. Oceanogr. Methods 7:761-770 (2009) | DOI: 10.4319/lom.2009.7.761

ABSTRACT: We present a psychotropic bacteria–based biosensor that can be used in low–temperature seawater for the analysis of nitrate + nitrite (NO_x^–). The sensor can be used to resolve concentrations below 1 µmol L^–1 at low temperature (<2.5°C) and high salinity (35‰), and in situ use in the deep sea was demonstrated by measuring NO_x^– profiles in sediment at 1500 m depth, where the temperature was 2.5°C. Analysis of marine sediment at 70 m depth showed very heterogeneous NO_x^– profiles, most of which exhibited pronounced maxima due to nitrification in the oxic surface layer. At this shallow water site, the in situ profiles were similar to profiles measured in the laboratory, but generally laboratory profiles appeared more uniform, presumably as a result of reduced fauna activity and disturbance of the microstructure of the sediment surface during core recovery.