“…The seeping water from the vent was at the same temperature but the salinity was 100 %. Seasonal changes of the environmental factors in the Thuwal seeps were exhibited in our recent study [25]. Approximate to the vent, the sediment under the microbial mat was composed mainly of CaCO 3 in the form of aragonite (26.7 %), calcite (29.5 %) and manganoan calcite (Ca(Mn,Ca)(CO 3 ) 2 ) (30.1 %).…”