Coupling of fog and marine microbial content in the near-shore coastal environment

[摘要] Microbes in the atmosphere (microbial aerosols) play an important role inclimate and provide an ecological and biogeochemical connection betweenoceanic, atmospheric, and terrestrial environments. However, the sources andenvironmental factors controlling the concentration, diversity, transport,and viability of microbial aerosols are poorly understood. This studyexamined culturable microbial aerosols from a coastal environment in Maine(USA) and determined the effect of onshore wind speed and fog presence ondeposition rate, source, and community composition. During fog events withlow onshore winds (<2 m s⁻¹) the near-shore deposition of microbialaerosols (microbial fallout) decreased with increasing wind speeds, whereasmicrobial fallout rates under clear conditions and comparable low windspeeds showed no wind speed dependence. Mean aerosol particle size alsoincreased with onshore wind speed when fog was present, indicating increasedshoreward transport of larger aerosol particles. 16S rRNA sequencing ofculturable ocean surface bacteria and microbial aerosols deposited onshoreresulted in the detection of 31 bacterial genera, with 5 dominant genera(Vibrio, Bacillus, Pseudoalteromonas, Psychrobacter, Salinibacterium) making up 66 % of all sequences. The sequence library from microbialaerosol isolates, as with libraries found in other coastal/marine aerosolstudies, was dominated at the phylum level by Proteobacteria, withadditional representation from Firmicutes, Actinobacteria and Bacteroidetes.Seventy-five percent of the culturable microbial aerosols falling out underfoggy conditions were most similar to GenBank-published sequences detectedin marine environments. Using a 97 % similarity cut-off, sequencelibraries from ocean surface and fog isolates shared eight operationaltaxonomic units (OTU's) in total, three of which were the most dominantOTU's in the library, representing large fractions of the ocean (28 %) andfog (21 %) libraries. The fog and ocean surface libraries weresignificantly more similar in microbial community composition than clear(non-foggy) and ocean surface libraries, according to both Jaccard andSorenson indices. These findings provide the first evidence of a differencein community composition and microbial culturability of aerosols associatedwith fog compared to clear conditions. The data support a dual role for fogin enhancing the fallout of viable microbial aerosols via increasedgravitational settling rates and decreased aerosolization stress on theorganisms, which may include relief from UV inactivation, desiccation, andoligotrophic microconditions. This study provides a strong case for ocean toterrestrial transport of microbes and a potential connection between waterquality and air quality at coastal sites.

[学科分类] 地球化学与岩石