4.7 Article

Legacy and dispersant influence microbial community dynamics in cold seawater contaminated by crude oil water accommodated fractions

Journal

ENVIRONMENTAL RESEARCH
Volume 212, Issue -, Pages -

Publisher

ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.envres.2022.113467

Keywords

Water accommodated fractions; Dispersant; Cold water; Microbial communities; Bioremediation; Crude oil

Funding

  1. Basque Government [IT1302-19]
  2. European Union [679266]
  3. University of the Basque Country
  4. Universite de Pau et des Pays de l'Adour
  5. H2020 Societal Challenges Programme [679266] Funding Source: H2020 Societal Challenges Programme

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The use of dispersants in cold water environments affects microbial communities and their degradation capacities, particularly in the presence of PAHs. The microbial community shows adaptability to the presence of PAHs and dispersants, with specific bacteria taxa potentially involved in PAHs degradation. Dispersants shape microbial community dynamics by stimulating potential dispersant-degrading taxa.
Dispersants, used for combating oil spills, increase hydrocarbon bioavailability promoting their biodegradation. Oil weathering process introduces harmful soluble hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), into the water column, resulting in water-accommodated fraction (WAF). The presence of dispersants can influence the weathering process by increasing PAHs solubility, toxicity and biodegradability. However, little is known on how dispersants affect microbial communities and their degradation capacities, especially in cold environment where low temperature decreases microbial activity and thus hydrocarbon degradation. Here, we investigated the microbial community dynamics in cold water contaminated by WAF prepared from crude oil with or without a commercial dispersant (Finasol OSR52). The WAFs, prepared with Naphthenic North Atlantic crude oil, were used to contaminate seawater from Norwegian cold sites, one oil-contaminated and the other pristine. The WAF-contaminated seawaters were maintained in microcosms at 4 degrees C for 21 days. The content of PAHs and microbial compositions (16S rRNA gene sequencing) were determined at days 0, 7, 14 and 21. In addition, the 96 h toxicity assay with adult Acartia tonsa revealed WAFs toxicity at days 0 and 21. The toxicity of WAF mixtures, with and without dispersant, against Acartia tonsa was reduced during the experiment, but PAHs removal was not increased. The water from the oil-contaminated site showed the highest PAHs removal revealing legacy effect (presence of microorganisms adapted to PAHs). Additionally, our results reveal: i) microbial community plasticity allowing the adaptation to the presence of PAHs and dispersant, ii) specific bacteria taxa probably involved in PAHs degradation, and iii) dispersants shape the microbial communities dynamics by stimulating potential dispersant-degrading taxa, such as Fusibacter. Thus, our results provide valuable insights on the role of microbial community in determining the fate of water-solubilized hydrocarbon in cold environment while questioning the role of dispersant used for fighting oil spill.

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