Increasing the conductivity of the electrolytes used in microbial electrochemical systems is an essential prerequisite to the large-scale success of these technologies. Microbial bioanodes formed from a salt marsh inoculum under constant acetate feeding generated up to 85 A*m-² in media containing 776 mM NaCl (45 g*L-¹, 1.5 times the salinity of seawater). These values were the highest salinities accepted by a microbial anode so far and the highest current densities reported with felt graphite electrodes.