Sulfate reduction Photosynthesis Formalin-killed control 坚 Light Microbial activity H2S measurements Killed Lactate Dark Time Time (a)Chemical assay (b)Photosynthesis measured in natural seawater with 14C02 Sulfate reduction 14C-Glucose respiration H2 present 圣 uolnJona Killed、 H2 absent Killed Time Time (c)Sulfate reduction in mud (d)Production of 14CO2 from 14C- 0measured with 35S02- glucoseChemical assay Photosynthesis measured in natural seawater with 14CO2 Sulfate reduction in mud measured with 35SO4 2- Production of 14CO2 from 14C￾glucose Microbial activity measurements