MICROBIAL INFLUENCED CORROSION ON ACCOMAC, A FRESHWATER, FERROUS-HULLED SHIPWRECK: EVALUATION OF MICROBIAL DIVERSITY AND COMPOSITION

Abstract

Abandoned shipwrecks are sitting at the bottom of oceans and lakes around the world, deteriorating extensively as the years pass by. Over time, however, microbial-comprised biofilm formation on these structures has resulted in the degradation of these structures and their integrity. The overall structure, abundance, and diversity of microbial communities on shipwrecks have only recently been studied in marine water environments. While previous studies have looked at the microbial communities associated with shallow water wrecks in marine environments, studies focusing on freshwater wreck systems are still unknown. The purpose of this study was to determine microbial community diversity trends and microbial community abundance taxa trends across the Accomac shipwreck. Furthermore, shipwrecks are colonized by corrosion-causing taxa, such as iron-oxidizing bacteria (FeOBs) and sulfate-reducing bacteria (SRBs) which have been shown to influence the biocorrosion of ferrous-hulled structures. Identification of the various microbes in biofilms, as well as corrosion-causing microbes, can help researchers understand the role they play in aquatic ecosystem development and persistence. A total of 44 Biofilm shipwreck samples were collected from various regions across the shipwreck, as well as 5 sediment samples and water samples which were also collected around the ship. DNA extractions on biofilm samples were conducted and sent for 16S amplicon sequencing to determine full community presence and diversity trends. Results suggest there was a statistically significant difference between the various sample types (i.e., biofilm, sediment, and water), indicating the microenvironments around the Accomac shipwreck influence the composition of the biofilm communities. The primary taxa responsible for significant differences between the microenvironments included Bacteroidata, Chloroflexi, and Cyanobacteria. Water samples had a higher taxa richness compared to shipwreck biofilm and sediment samples, indicating the mixing of water due to current movements aids in biofilm diversity and microbial community composition. Microbial diversity was not affected by the distinct side of the wreck (i.e., port side vs starboard side), and each had a similar community makeup. This suggests that the increase wave action on the port side of the wreck didn't influence community composition. Water depth was a statistically significant factor influencing the clustering of amplicon sequence variants (ASVs) at the different sample locations (i.e., waterline, below waterline). This suggests that greater depths influence the taxonomic makeup of biofilm communities. Overall, the results from this study showed similar trends in microbial community assemblages which were influenced by the microenvironment they were found in, shallow wrecks are similar to those seen in marine systems indicating similar microbes play a role in biofilm formation.