Tracing the dynamic ecology of microbial biofilms on steel with prolonged submersion in surface water

Amplicon sequencing is applied to monitor microbial species residing in the biofilm that formed on steel surface submerged in surface water along the Ghent Terneuzen canal, stretching 31 kms from Belgium to the Netherlands. Temporal and spatial differences in the biofilm microbiota were revealed by 16S rRNA composition analysis. The loss-of-mass from S235 steel coupons showed uniform corrosion rates ranging from 242 to 906 g/m 2 after 3 months. Notably, enhanced pitting corrosion was seen at one specific location near ‘Heide’ affecting the surface with depths up to 1210 µm after 6 months. We presume the excessive steel deterioration in micro-cavities is associated with microbial activity of iron-oxidising bacteria (IOB) and sulphur-reducing bacteria (SRB), such as Shewanella spp . and Gallionella spp., respectively, as redox-active species. Indications for microbially induced corrosion (MIC) are highlighted at sites with apt microbial composition, irrespective of physico-chemical water parameters. Coupons affected by high corrosion and assumed MIC did not stand out in terms of species richness and alpha diversity did not increase, suggesting partial take-over of the microbial community by IOB or SRB.