Organic-N loss by efflux and burial associated with a low efflux of inorganic-N and with nitrate assimilation in Arctic sediments (Svalbard)

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1996 (English)In: Mar. Ecol. Prog. Series, no 141, p. 283-293Article in journal (Refereed)

Abstract [en]

Sediments were sampled at water depths from 170 to 2577 m at 17 stations adjacent to Svalbard. In general, with increasing water depth there was decreasing NH4+ with increasing NO3- in the sediment pore water, increasing depth of O2 penetration, decreasing NH4+- and increasing NO3--efflux rates, decreasing nitrification and denitrification rates, and decreasing rates of organic nitrogen burial. Most sediments had insignificant rates of nitrogen mineralisation (0 to 0.34 mmol m-2 d-1); there was a very high C:N ratio (mean 68) in the measured efflux products. Efflux and consumption rates of NO3-, calculated from pore water profiles, were generally higher than the measured rates, but these calculated rates also predicted high C:N mineralisation ratios. The high ratios demanded that the particulate organic substrate must also have had a low nitrogen content. The high measured efflux of dissolved organic nitrogen (mean 0.93 mmol m-2 d-1) from the sediment suggested that fresh detritus (C:N 13) might reach the sediment surface, and be hydrolysed with efflux loss of dissolved nitrogen-rich organic matter (e.g. C:N 6) and with subsequent mineralisation (C:N ~68) or burial (C:N ~10) of the transformed material. High C:N ratios in the products of sediment mineralisation are commonly reported, indicating the prevalence of preferential nitrogen loss from detritus in the water column and probably also at the sediment-water interface. The retention of nitrogen by the sediment can explain the discrepancy between measured and calculated NO3- fluxes: NO3- did not escape from the sediment to the water because it was assimilated by bacteria utilising high C:N substrate. It is likely that some NO3- which diffused downward was also assimilated rather than denitrified. Many of these sediments had a sub-surface zone of NH4+ production associated with nitrification. Above and below this zone of net production were zones of NH4+ and NO3- disappearance.

Place, publisher, year, edition, pages

1996. no 141, p. 283-293

Keywords [en]

sediments, EPOS II, SEAS, Arctic, Svalbard, Nitrate, Ammonium, DON, Assimilation, C:N, Nitrification, Denitrification, Burial

Identifiers

URN: urn:nbn:se:polar:diva-223DOI: 10.3354/meps141283 ISBN: Print ISSN:0171-8630; online ISSN:1616-1599 (print)OAI: oai:DiVA.org:polar-223DiVA, id: diva2:568354

Note

Source: Polardok by Swedish Polar Research Secretariat

Available from: 2012-11-15 Created: 2012-11-15 Last updated: 2012-11-15

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