Biogeochemistry and Biology of CO2 and pH Extremes

Among the different extreme environments on Earth, those varying in CO2 concentration pose a variety of challenges for different life forms. In this session, we would like to invite presentations dealing with field based and experimental studies on aquatic/sedimentary ecosystems and biogeochemical functioning under CO2 and pH extremes. How are CO2 concentrations and corresponding pH levels affecting the habitability of an ecosystem? What are threshold levels for changes in organism performance, community structure, biodiversity, and metabolic functioning? By which mechanisms can organisms adapt to or counteract the effect of CO2 and pH extremes? What are the peculiarities of carbon cycling and other biogeochemical processes in such extreme environments? One focus of the session will be how extreme CO2 and pH environments can serve as natural analogues, e.g. acidic CO2 vents for CO2 leakage from carbon dioxide capture and storage in the terrestrial subsurface and/or deep-sea, or for different levels of ocean acidification; and high pH vents for unique carbonate habitats for microbial life formed by serpentinization.