A new deep-sea probe for in situ pH measurement in the environment of hydrothermal vent biological communities

In situ measurements have been shown to be the most relevant means to chara cterise the chemical properties of the highly dynamic medium surrounding hy drothermal vent organisms. However, few instrumental devices can perform su ch measurements at great depth, and there is great need to extend the range of chemical parameters that can be determined in situ. To investigate the spatial and temporal variations of pH within the habitats of vent organisms , a deep-sea probe was developed and successfully tested during the HOPE'99 diving cruise (13 degreesN, East Pacific Rise). In situ measurements allow ed us to quantify the pH range over different biological communities, highl ighting differences between the habitats, as well as micro-scale variations . As pH is expected to play a significant role in major biogeochemical proc esses occurring in the seawater/fluid-mixing zone, this probe should be of great utility for the study of interactions between vent communities and th eir environment. (C) 2001 Elsevier Science Ltd. All rights reserved.