FIG. 3.

Vertical profiles of organic matter mineralization rates in Black Sea sediments from station I (top) to station IV (bottom). Circles, ΣCO₂ production; squares, NH₄⁺ accumulation; diamonds, sulfate reduction. Error bars indicate standard errors from linear regressions (ΣCO₂ and NH₄⁺) and standard deviations of triplicate sulfate reduction rates. Note different scales for different processes. At each station, the three scales are plotted at the ratio 11.2:1:5.6 for ΣCO₂ production/NH₄⁺ accumulation/sulfate reduction, corresponding to the inferred stoichiometric ratio of these processes during sulfate reduction (see text for details).