Figure 4.

(Gray) Microprofiles of pH (triangle) and ΣH₂S (circles) measured in cores incubated under oxic overlying water for 27 days and successively exposed to anoxic overlying water containing 200 μM NO₃⁻ for 9 days (oxic to anoxic+NO₃⁻). For comparison, pH microprofiles measured in the same core before the change in overlying water conditions (open triangles) (oxic) and pH microprofiles measured in cores only exposed to the NO₃⁻ treatment (black triangles) (anoxic+NO₃⁻) are shown (these profiles correspond to the profiles shown in Figure 3). Data are shown as mean±s.e.m. (n=3).