Concentration and Viability of Airborne Bacteria Over the Kuroshio Extension Region in the Northwestern Pacific Ocean: Data From Three Cruises

Abstract

Airborne bacteria have been shown to act as condensation and ice nuclei in mixed‐phase clouds and are consequently hypothesized to have significant effects on atmospheric processes and even the global climate. However, few data are available regarding their concentration and variation in the air over the open ocean. Aerosol samples were collected during three cruises in the early summers of 2013, 2014, and 2016 over the Kuroshio Extension region of the northwest Pacific Ocean. The concentrations of viable and nonviable bacterial cells in the marine surface air were quantified using epifluorescence enumeration with the LIVE/DEAD BacLight stain. The concentrations of total bacteria varied between 1.0 × 104 and 2.5 × 105 cells m−3 and averaged 5.2 × 104, 1.0 × 105, and 7.5 × 104 cells m−3 in the three respective cruises. The viabilities, i.e., the ratios of the concentration of viable bacterial cells to that of total bacterial cells, ranged from 80% to 100% (average 93%), and the respective means were 93%, 89%, and 96% in the cruises. The total bacterial concentration had a close correlation with the wind speed near the sea surface, and the bacterial viability correlated negatively with the air temperature, sea surface temperature, and concentration of coarse particles (size > 1 μm). The deposition and sea spray fluxes of bacteria were roughly estimated as hundreds of cells m−2 s−1 on average. The limited data on bacterial concentration and viability from the three cruises indicate the rapid air‐sea exchange of bacteria over the Kuroshio Extension region of the northwest Pacific Ocean.

Large Increases in Primary Trimethylaminium and Secondary Dimethylaminium in Atmospheric Particles Associated With Cyclonic Eddies in the Northwest Pacific Ocean

“…Thus, the satellite‐derived concentrations of chlorophyll‐ a alone cannot explain the highest observed values. Hu et al () observed the highest bacterial abundance in the atmosphere on 25 June 2014 near the largest cyclonic eddy, which represents the continuance of the largest cyclonic eddy in April. Bacteria and nutrients may be pushed to the surface by upwelling in cyclonic eddies (Chang et al, ; Hu et al, ; Kouketsu et al, ; Zhang et al, ); afterward, they may rapidly degrade organic matter at the surface (Letscher et al, ).…”

“…Hu et al () observed the highest bacterial abundance in the atmosphere on 25 June 2014 near the largest cyclonic eddy, which represents the continuance of the largest cyclonic eddy in April. Bacteria and nutrients may be pushed to the surface by upwelling in cyclonic eddies (Chang et al, ; Hu et al, ; Kouketsu et al, ; Zhang et al, ); afterward, they may rapidly degrade organic matter at the surface (Letscher et al, ). Recently, organic matter pools consisting of relatively small molecules have been reported in the surface waters of various oligotrophic open oceans (Jennings et al, ; Quinn et al, ; Wurl et al, ; Zäncker et al, ), but the observed concentrations of chlorophyll‐ a in surface water have been low.…”

“…Recently, organic matter pools consisting of relatively small molecules have been reported in the surface waters of various oligotrophic open oceans (Jennings et al, ; Quinn et al, ; Wurl et al, ; Zäncker et al, ), but the observed concentrations of chlorophyll‐ a in surface water have been low. In the presence of wind speeds larger than 5.4 m/s, bacteria together with organic matter may be transported from the organic matter pool to the marine atmosphere by bubble bursting, and the enrichment of sea‐spray aerosols with organics increases with decreasing particle size (Gantt & Meskhidze, ; Hu et al, ; Quinn et al, ; Quinn et al, ; Quinn & Bates, ). These results imply that the elevated levels of DMA + and TMA + are very likely due to the release of sea‐spray aerosols and/or gaseous precursors from the cyclonic eddy under high wind speeds.…”

Bubble-mediated transport of benthic microorganisms into the water column: Identification of methanotrophs and implication of seepage intensity on transport efficiency

“…Additional microorganisms may have been introduced through sediment that was resuspended by wind and wave action 4,5 . Air-borne contamination during sample handling and filtration were likely low, due to the differences in cell concentration of air (10 3 −10 7 cells m −3 ) 56 and sample water (10 10 -10 11 cells m −3 ).…”

Supplementary material to "Abundance and viability of particle-attached and free-floating bacteria in dusty and nondust air"

“…The flow rate for the BioSampler/holder was 10−12.5 L min -1 , and the collection duration was 1−2 hours. More details on sample collection with the BioSampler and the in-line holder are available in Murata and Zhang (2016) and Hu et al (2017), respectively. The discrepancy between the results of the Andersen sampler and the other two samplers might have been caused by the different sampling durations and collection efficiencies of the samplers (e.g., for the Andersen sampler, there was a loss of bacteria due to bouncing, and the size fraction smaller than 0.43 m was missing).…”