Effects of dispersant on the petroleum hydrocarbon biodegradation and microbial communities in seawater from the Baltic Sea and Norwegian Sea
Dispersants have been used in several oil spill accidents, but there is little information available on their effectiveness on Baltic Sea conditions with brackish and cold seawater. This study investigated the effects of dispersant use on petroleum hydrocarbon biodegradation rate and bacterial community structure. Microcosm experiments were conducted at 5 °C for 12 days with North Sea crude oil and dispersant Finasol 51 with coastal and open sea Gulf of Finland and Norwegian Sea seawater. Petroleum hydrocarbons concentration were analysed with GC-FID. Bacterial community structure was studied using 16S rDNA gene amplicon sequencing and petroleum hydrocarbon gene abundances with quantitative PCR. Highest oil degradation gene abundances and oil removal were observed in microcosms with coastal seawater from Gulf of Bothnia and Gulf of Finland, respectively, and lowest in the seawater from the Norwegian Sea. Dispersant addition was not observed to enhance oil biodegradation. Dispersant usage caused apparent effects on bacterial communities in all treatments.