Microbial Communities Associated with Alternative Fuels in Model Seawater-Compensated Fuel Ballast Tanks

Abstract

The biocorrosion of carbon steel poses a risk for ships combining seawater and fuel in metal ballast tanks. Ballast tanks were simulated by duplicate reactors containing carbon steel coupons and either petroleum F76 (petro-F76), Fischer–Tropsch F76 (FT-F76), or a 1:1 mix of both fuels, to investigate whether the alternative fuel FT-F76 influenced this risk. The polycarbonate reactors were inoculated with seawater, and the control reactors did not receive fuel. The reactors were monitored for 400 days, and they all reached a pH and open circuit potential where elemental iron was oxidized, indicating corrosion. The reactors containing petro-76 or fuel mix had higher levels of dissolved iron; one of each replicate had lower concentrations of sulfate than the original seawater, while the sulfate concentration did not decrease in the other incubations. The high sulfate reactors, but not the low sulfate reactors, had a high relative abundance of microaerophilic sulfide-oxidizing bacteria. The FT-F76 and the no-fuel reactors had a high relative abundance of iron-sequestering Magnetovibrio. Although dissolved iron and loss of sulfate under anoxic conditions are associated with biocorrosion, our results suggest that in our reactors these indicators were altered by iron-sequestering and sulfide-oxidizing microbes, which is consistent with the slow diffusion of oxygen across the polycarbonate reactors.

Microbial Communities in Model Seawater-Compensated Fuel Ballast Tanks: Biodegradation and Biocorrosion Stimulated by Marine Sediments

“…croflora. A low rate of oxygen diffusion across the polycarbonate housing the reactors was hypothesized as a reason for the limited sulfate reduction activity and the possible promotion of sulfide oxidation [39][40][41][42] consistent with the detection of a high relative abundance of sulfide-oxidizing bacteria in two of the reactors [18]. The relatively low levels of sulfate reduction and dissolved iron suggested that the rate of corrosion was relatively slow.…”

“…Duplicate reactors containing 24 coupons (1018 carbon steel, Metal Samples, Munford, AL measuring 1.3 cm × 7.6 cm × 0.15 cm) were inoculated with approximately 2550 mL of seawater from San Diego Bay Harbor (San Diego, CA, USA) and a total of 120 mL of either petro-or Fischer-Tropsch F76 (FT-F76) fuel or a 50:50 mix of both fuels (Figure 1 and Table 1) and were incubated for 400 days. Note that approximately 6 × 10 −6 moles of oxygen were diffused into a reactor per day [49] based on the oxygen permeability properties of the polycarbonate used in the construction of the reactor [18]. untreated nonsterile sediments consisting of a slurry of 100 mL of seawater and a 100 g (wet weight) sediment.…”

“…Furthermore, the low relative abundance of hydrocarbon-degrading bacteria suggested that the fuel-amended seawater reactors did not have conditions that were particularly conducive to fuel biodegradation. A component not included in the Dominici et al [18] study was the inclusion of a marine sediment. In another laboratory study of biocorrosion using a variety of naval fuels, carbon steel coupons, and marine inocula [21], the degree of both general and pitting corrosion was positively correlated with the loss of the sulfate, implicating sulfate-reducing bacteria as major contributors to MIC.…”

Novel oil-associated bacteria in Arctic seawater exposed to different nutrient biostimulation regimes

“…Halarcobacter was among the microbial groups recently identified in fuel reactors containing PetroF76 and FT-F76, along with other putative hydrocarbon degraders such as Marinobacter (81). Candidatus Pseudothioglobus singularis, a newly described Gammaproteobacteria, is a group that has been intensively characterized as a representative culture from within the SUP05 clade for its utilization of organic carbon and methylated amines for energy acquisition in marine environments (82).…”

“…Candidatus Pseudothioglobus singularis, a newly described Gammaproteobacteria, is a group that has been intensively characterized as a representative culture from within the SUP05 clade for its utilization of organic carbon and methylated amines for energy acquisition in marine environments (82). Nevertheless, until now Halarcobacter and Pseudothioglobus have not been investigated for genes or biosurfactants related to hydrocarbon degradation (81). Genomic inspection revealed here that Halarcobacter anaerophilus and Candidatus Pseudothioglobus singularis possess alkG rubredoxin and meta-cleavage pathway genes that could potentially be responsible for aromatic compound metabolism, suggesting roles for these populations in crude oil bioremediation in cold Arctic waters.…”