Metagenomic insights into nutrient and hypoxic microbial communities at the macrofouling/steel interface leading to severe MIC

Abstract Adherent macrofouling in marine environments caused complex corrosion of steel surfaces, resulting in localized corrosion at the oyster/steel interface and uniform corrosion at the ascidian/steel interface. Sulfate-reducing bacteria (SRB) have been implicated in the microbiologically influenced corrosion (MIC) process at macrofouling-covered interfaces. To better understand the role of marine biofilms as key mediators in the MIC process, metagenomic techniques were used to study microbial communities and their response to macrofouling’s coverage. Compared to ascidians, the formed local anaerobic zone at oyster/steel interface stimulated the growth of SRBs, leading to higher FeS content and severe localized corrosion. SRB Desulfovibrio and Desulfobulbus, along with the SRB-related functional gene dsr, were found to increase, while oxygen-related function genes coxC, ccoN, ccoO, ccoP, and ccoQ decreased. In contrast, steel surfaces without macrofouling coverage had the richest microbial communities, yet experienced less severe MIC, suggesting no direct connection between microbial abundance/diversity and steel corrosion promotion.