FORMATION OF NESQUEHONITE AND OTHER MINERALS AS A CONSEQUENCE OF BIOFILM DEHYDRATION

A microbial biofilm community was established over 971 days within gra vel in an aquarium so as to model biofouling of an aquifer. When the w ater was allowed to evaporate slowly, white crystalline deposits, cont aining several carbonate and sulphate minerals including nesquehonite (MgCO3.3H(2)O), were seen at the highest points on the surface of the biofouled gravel. No such deposits occurred in regions lacking biofilm s. These crystals appeared to originate from evaporation of dissolved salts which had migrated through the biofilm. Surface-adherent microbi al biofilms may conceivably provide a conduit for solute transport in porous media such as soils and aquifers.