Nitrogen fluxes through the lower estuary of the river Great Ouse, England:the role of the bottom sediments

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 163:109-124 (1998) - doi:10.3354/meps163109 Nitrogen fluxes through the lower estuary of the river Great Ouse, England: the role of the bottom sediments M. Trimmer1, D. B. Nedwell1,*, D. B. Sivyer2, S. J. Malcolm2 1Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, United Kingdom 2Centre for Environment Fisheries and Aquaculture Sciences, Pakefield Road, Lowestoft, Suffolk NR33 0HT, United Kingdom *Addressee for correspondence. E-mail: [e-mail] Sediment-water nutrient exchange, oxygen uptake, denitrification (acetylene blockage) and pore water nutrient concentration profiles were measured at intertidal sediment (predominantly silt/clays) sites in the lower estuary of the river Great Ouse, England. Sediments were consistent sinks for NO3- (310 µmol m-2 h-1, mean sites 4 to 9) and O2 (2800 µmol m-2 h-1, mean sites 4 to 7), sources of NH4+ (270 µmol m-2 h-1, mean sites 4 to 9) but neutral with respect to NO2- and urea. Oxygen uptake was significantly correlated (p < 0.05) with seasonal temperature. Nitrate exchange became saturated at NO3- concentrations > 400 µM, at a rate of about 400 µmol NO3- m-2 h-1. Denitrification accounted annually for 46% of the NO3- exchanged into the sediments and approached asymptotic rates during spring and summer at NO3- concentrations > 400 µM. Of the total N flux through the sediments, NH4+ efflux accounted for 51%, whilst 49% was converted to gases, compared to >90% in the upper estuary. Freshwater flushing times were calculated for a defined area of the estuary and ranged from 20.5 d in June to 3.25 d in November. Attenuation of the riverine total oxidised nitrogen (NO3- + NO2-) load to the estuary ranged from 1% in the middle of winter to 56% at the height of summer and annually the sediments denitrified 38.4 Mmol N. Recycling of nitrogen in the sediments, via NO3- ammonification (calculated by difference) and organic ammonification, generated an annual NH4+ efflux of 128 Mmol N, equivalent to 22% of the primary production N requirement in the Wash. Bottom sediments · Denitrification · Freshwater flushing · Nutrient attenuation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 163. Publication date: March 12, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.