Global Comparison of the Bacterial Communities of Bilge Water, Boat Surfaces, and External Port Water

Abstract

In the past, ballast water has been a key vector in the ship-mediated dispersal of invasive species. Here, we evaluate the potential for port microorganisms to enter and colonize the hull and bilge water of ships. Due to the small size and ubiquitous nature of bacteria, they also have the potential to be spread through hull fouling and bilge water discharge. The goal of this study was to identify the extent to which the boat microbial community is shaped by the microbial community in the port water where the boat spends most of its time. Here, we compared the microbial communities of the hull and bilge compartments of 20 boats to those of the port water in 20 different ports in five regions around the world. We found that there was a significant difference in microbial diversity between boat and port microbial communities. Despite these differences, we found that Cyanobacteria were present at high abundances in the bilge water of most vessels. Due to the limited light in the bilge, the presence of Cyanobacteria suggests that port microorganisms can enter the bilge. Using source-tracking software, we found that, on average, 40% of the bilge and 52% of the hull microbial communities were derived from water. These findings suggest that the bilge of a vessel contains a diverse microbial community that is influenced by the port microbial community and has the potential to serve as an underappreciated vector for dispersal of life. IMPORTANCE Invasive species have been a worldwide problem for many years. However, the potential for microorganisms to become invasive is relatively underexplored. As the tools to study bacterial communities become more affordable, we are able to perform large-scale studies and examine bacterial communities in higher resolution than was previously practical. This study looked at the potential for bacteria to colonize both boat surfaces and bilge water. We describe the bacterial communities on boats in 20 shipping ports in five regions around the world, describing how these microorganisms were similar to microorganisms found in port water. This suggests that the water influences the bacterial community of a boat and that microorganisms living on a boat could be moved from place to place when the boat travels.

Impact of air, water and dock microbial communities on boat microbial community composition

“…16S rRNA sequence processing followed a similar process to the one described in Schaerer et al . (2019). The complete pipeline for our analysis can be found at https://github.com/lgschaer/boatbiome.…”

“…Denoised reads were merged, bimeric reads were removed and ASVs were assigned using the Silva database v132. 16S rRNA sequence processing followed a similar process to the one described in Schaerer et al(2019). The complete pipeline for our analysis can be found at https://github.com/lgsc haer/boatbiome.…”

“…We previously characterized microbial communities of boats and shipping ports around the world (Schaerer et al 20192020…”

“…). Using source tracking software, we identified that, on average, about 40% of the bilge microbial community and 52% of the boat surface microbial community were sourced from the water (Schaerer et al 2019…”

“…Here, in addition to the microbial community in water, we explore other sources which we expect to influence the boat microbial community. Our previous work primarily focused on water as a source of non‐native species to the bilge water and boat surface (Schaerer et al 2019…”