The effect of hydrostatic pressure on the activity and community composition of hydrocarbon-degrading bacteria in Arctic seawater
Bibliographic record
Abstract
ABSTRACT There is a renewed interest in hydrocarbon biodegradation in Arctic seawaters due to increasing ship traffic and risk for oil spills. Most studies, however, fail to address the effect of increasing pressure as an environmental parameter. Here, we conducted a series of pressurized enrichments (0.1–30 MPa, 4°C) inoculated with a 100-day-old hydrocarbon-degrading biofilm collected from 615 m deep in Arctic seawater. Cell-specific CO 2 production rates provided a clear summary of the observed microbial activity: a bloom of a hydrocarbon degrading-biofilm generating 0.82–0.90 fmol CO 2 ⋅bacterial gene −1 ⋅day −1 at 0.1–8 MPa, but undetectable activity at 30 MPa until day 6. At 30 MPa, the microbial activity increased between days 6 and 34 with an average rate of 0.36 ± 0.08 fmol CO 2 ⋅bacterial gene −1 ⋅day −1 . Amplicon sequencing revealed no differences in the microbial community composition at 0.1–12 MPa. While the typical Arctic alkane degraders Oleispira and Shewanella were abundant across all hydrostatic pressures and over time, Colwellia, Neptunomonas , and Kiloniella were significantly enriched solely at 30 MPa. Our results suggest that the physiological adaptations of psychrophilic bacteria to thrive at sub-zero temperature make Arctic oil degraders tolerant to mild hydrostatic pressures of up to 12 MPa, whereas temperate climate communities have shown hydrostatic pressure-induced inhibition at 10–15 MPa in comparable studies. The activity of hydrocarbon degraders in sinking marine oil snow in the Arctic may remain unaffected down to depths of about 1,200 m, after which hydrostatic pressure can significantly affect hydrocarbon degradation at increasing depths down to 3,000 m. IMPORTANCE Increased ship traffic in the Arctic region raises the risk of oil spills. With an average sea depth of 1,000 m, there is a growing concern over the potential release of oil sinking in the form of marine oil snow into deep Arctic waters. At increasing depth, the oil-degrading community is exposed to increasing hydrostatic pressure, which can reduce microbial activity. However, microbes thriving in polar regions may adapt to low temperature by modulation of membrane fluidity, which is also a well-known adaptation to high hydrostatic pressure. At mild hydrostatic pressures up to 8–12 MPa, we did not observe an altered microbial activity or community composition, whereas comparable studies using deep-sea or sub-Arctic microbial communities with in situ temperatures of 4–5°C showed pressure-induced effects at 10–15 MPa. Our results suggest that the psychrophilic nature of the underwater microbial communities in the Arctic may be featured by specific traits that enhance their fitness at increasing hydrostatic pressure.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".