Browsing by Subject "dispersant"

Heavy traffic and transportation of crude oil makes the Baltic Sea vulnerable to accidental oil spills. Currently mechanical removal is the recommended response method in the Baltic Sea region. However, in bad weather conditions, mechanical oil removal can be challenging, and it may be justifiable to consider alternative response methods in order to protect valuable natural sites. Chemical dispersants are mixtures of surfactants and solvents and are used to treat spilled oil in marine environments. Dispersants break oil slicks into small droplets, which are more readily available for microbial biodegradation. Large-scale studies on the effects of dispersants on microbial communities and biodegradation rates have not been conducted in the Baltic Sea. During this 40-day microcosm study, native microbial communities from the Gulf of Finland were exposed to crude oil, dispersant or their combination. Additional nutrients were not supplied during the study. The experiment was carried out at 10 °C, and samples were collected at days 1, 2, 5, 14 and 40. The amount and expression of genes related to microbial abundance, oil biodegradation and nutrient cycling was assessed by quantitative PCR. Extracellular enzymatic activities of microbes were studied utilizing high throughput robotics. The results indicated that microbial response was primarily elevated in samples containing dispersant. Dispersant was degraded almost completely during the study period. Biodegradation of C21-40 hydrocarbons in crude oil was not enhanced with the addition of dispersant. On genetic level, the abundance and expression of alkane monooxygenase gene (alkB) was elevated in samples with dispersant, whereas the abundance and expression of polycyclic aromatic ring-hydroxylating dioxygenase gene (PAH-RHD) was enhanced also in samples containing crude oil.