Organic degradation, sulphate reduction and ammonia production in the sediments of Loch Eil, Scotland

S. J. Malcolm, N. S. Battersby, S. O. Stanley, C. M. Brown

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    The rates of degradation and mineralization of organic matter in sediments from two stations in Loch Eil were studied. A particular feature of this site is a major input of cellulose fibre from a pulp and paper mill which affected both sediments and benthic fauna, the input may be regarded as an additional terrigenous input having a high C:N ratio. The effect of this input on organic degradation, sulphate reduction and ammonia production was determined in both field samples and using sediment incubation experiments. The result of the cellulose input is a spatial condensation of the normal biogeochemical zones in the sediment bringing the sulphate reducing zone to the sediment surface at E70, the station receiving the highest input. Rates of sulphate reduction are comparable to those measured at other sea loch sites and differences between the rates of sulphate reduction measured by 35SO42- technique and jar incubation are demonstrated. Alkalinity and ammonium production may be related to sulphate reduction by previously accepted stoichiometry and model calculations suggest that the organic matter being mineralized in the sulphate reducing zone has a C:N ratio similar to that in marine planktonic material (E70 ~ 7; E24 ~ 8). At E70 there is apparently production of ammonia in excess of that produced by sulphate reduction. The potential for nitrate reduction to ammonia was demonstrated in the surface sediments. Degradation of cellulose, which was active only in the near surface sediments, was not related directly to sulphate reduction and it is suggested that this is due to production of organic intermediates and cell carbon; only a percentage of the carbon being mineralized. Comparison of estimated inputs of organic carbon to the sediments with the turnover of sulphate suggests that sulphate reduction can account for degradation of an amount of carbon equivalent to the total estimated primary production in Loch Eil, about half the total carbon input. Mineralization of carbon by aerobic and anaerobic processes appears to balance the estimated input of carbon but this does not account for the carbon content of the sediments (up to 8%) and it is suggested that net mineralization has been overestimated. © 1986.

    Original languageEnglish
    Pages (from-to)689-704
    Number of pages16
    JournalEstuarine, Coastal and Shelf Science
    Issue number5
    Publication statusPublished - Nov 1986


    • ammonia
    • cellulose
    • degradation
    • derivatives
    • interstitial water
    • organic matter
    • Scotland coast
    • sediments
    • sulphates


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