Oil biodegradation and marine oil snow formation in Arctic seawater microcosms at 4 °C

In Arctic seawater microcosms incubated at 4 °C for 6 weeks with 1% (v/v) UV-weathered Churchill diesel, oil amendments sharply increased specialized oil-degrading taxa, including Pseudomonas and Pseudoalteromonas.

• Why it matters: Declining sea-ice duration can extend ice-free seasons and increase exposure to oil spills, but microbial biodegradation and marine oil snow (MOS) formation under cold conditions remain poorly quantified.
• What they did: Seawater microcosms were amended with UV-weathered Churchill diesel at 1% (v/v), then tracked by 16S rRNA sequencing and MOS aggregate measurements after nutrient biostimulation (NaNO3, KH2PO4) and an alternative dispersant at 0.1% (v/v).
• The result: Nutrient plus dispersant biostimulation increased MOS aggregates and rapidly enriched oil-degraders, while n-alkanes showed the highest biodegradation loss; UV weathering caused a 22% PAH loss, and biostimulation increased transfer of high molecular weight alkanes and PAHs into the aqueous phase.

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