Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Oxic and sub-oxic N.-E.Atlantic sediments were examined for sulphate-reducing activity.Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied.A low rate of sulphate reduction (0.1 nmol SO2-/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphatereducing bacteria (SRB).A higher activity of sulphate reduction (2.2 nmol SO2-/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity.This sediment contained approx.102-103 acetate, lactate and propionate oxidising SRB/ml.No low-M r organic acids were detected in these sediments.However,