Figure 2

Temporal changes in concentrations of dissolved iron and hydrogen sulfide in diffuse fluids from the Bio9 area. The increase in iron coincides with the appearance of rusty spots in the tubeworm colony (black arrow). The two horizontal lines represent the maximum concentrations of sulfide (dashed) and iron (continuous) that can be oxidized by seawater with an oxygen concentration of 100 μM. Iron is the limiting reactant over the whole time period, in contrast to sulfide, which is oxygen limited, except for the conditions in November 97.