On the basis of previous studies at 9 degrees N and 13 degrees N East Pacific Rise (EPR) fields, we discuss the general assumption that temperature is a proxy for sulfide in vent fauna habitat. The main conclusion of these works is illustrated here through selected examples. In situ measurements were used to assess the variability of chemical parameters as function of temperature at the scale of fauna aggregations. Over a single vent site, aggregations of mussels or Riftia pachyptila discretely distributed around diffuse vents exhibit, in first assumption, similar sulfide-temperature correlation. In contrast, sulfide is much higher, for a given temperature, in the habitat of alvinellids than in neighboring habitats of Riftia pachyptila. Some consistency in the sulfide-temperature correlation is also found when comparing diffuse vent habitats over distinct sites of the vent field, even when they are not dominated by the same species. In some case, however, this correlation departs substantially from the general trend. The variability in the iron-sulfide ratio in fluids between site is further expected to modulate sulfide biological impact. According to thermodynamic calculation, however, this factor appears to be more relevant when used to discriminate sulfide toxicity in alvinellid habitats than to conclude on the unavailability of sulfide to Riftia pachyptila populations at iron-rich sites. When direct in situ characterization is not available, these general conclusions should provide a first basis for the extrapolation of chemical features from temperature ranges in EPR habitats.