| Bioaerosols are ubiquitous in the atmosphere and are an important vehicle for the airborne spread of microorganisms.In addition,microorganisms in bioaerosols can act as cloud condensation nuclei(CCN)and ice nuclei(IN)to affect the microphysical properties of clouds and have an important impact on precipitation processes,radiative forcing and global climate change.The ocean is an important source of bioaerosols in the atmosphere.However,there are few studies on the diversity and potential sources of microorganisms in remote marine aerosols.In order to deeply understand the physical and chemical properties and influencing factors of marine bioaerosol and restrict the aerosol model in the climate model,it is of great significance to further improve the assessment of the climate effect of aerosol by observing the microbial characteristics and ice nucleation activity of marine biological aerosol in the field.Based on the aerosol samples collected during the 33rd Antarctic Scientific Expedition(CHINARE 2016/2017),the first "Xiang Yang Hong" Global Scientific Expedition and the 9th Arctic Scientific Expedition(CHINARE 2018),using high-throughput sequencing technology,combined with meteorological parameters,air mass trajectory inversion,water-soluble ions,organic carbon,sugar alcohols and other chemical compositions,this paper discussed the microbial community characteristics and factors affecting the distribution of marine aerosol samples under the current climate change.The main contents and conclusions are as follows:1、Revealing the spatial distribution characteristics of microbial communities in remote marine bioaerosols(1)Bacterial aspects:The bacterial communities in the aerosol of Antarctic coastal,the South Atlantic Ocean,the Indian Ocean and the Western Pacific Ocean at the phylum level were mainly composed of Proteobacteria,Bacteroidetes,Firmicutes and Actinobacteria,which have also been found in other marine aerosol.The dominant presence of these four phyla have also been found in other marine aerosol environments,suggesting that there may be a common(core)bacterial community in marine aerosol environments.However,there were spatial differences in the distribution of bacteria in aerosols from different sea areas at the genus level,with the highest relative abundance of the genus Sphingomonas in Antarctic coastal aerosols;the highest relative abundance of the genus Sulfurovum in South Atlantic aerosol samples;and the highest relative abundance of the genus Microbacterium in Indian Ocean and Western Pacific aerosol samples.In addition,abundant functional bacteria have been found in marine aerosol in Antarctic coastal,the South Atlantic Ocean,the Indian Ocean and the Western Pacific Ocean,which have potential influence on the geochemical cycle.(2)Fungal aspects:Marine fungal aerosols collected from the central Arctic Ocean,the Canadian Basin,the Chukchi Sea,the Bering Sea,the Okhotsk Sea,and the Northwestern Pacific Ocean showed some spatial variation in fungal abundance and community composition structure.Ascomycota were widely present in the marine fungal aerosols from these six areas,and Basidiomycota were relatively more abundant in aerosol samples from close to the coast.Fusarium,Diaporthe,Aspergillus and Boeremia were dominant in all marine fungal aerosols,and Cladosporium were detected in abundance in aerosol samples from low-latitude sea areas.2、Potential factors affecting the distribution of microbial communities in remote marine bioaerosols at spatial scales were analyzedThe potential effects of microbial community distribution in remote bioaerosols were explored in terms of geographical location,air mass transport,and environmental variables(environmental and meteorological factors).(1)For bacteria,the distribution of bacterial communities in Antarctic coastal aerosols were affected by regional transport(sea-air exchange),long-range transport of oceanic and Antarctic continental air masses,temperature,wind speed and organic carbon concentration.Geographic location did not significantly affect community distribution.In contrast,significant distance-decay biogeographic distribution patterns were found in bacterial communities in the South Atlantic Ocean,the Indian Ocean,and the Western Pacific Ocean aerosols.The spatial distribution of dominant bacterial genera such as Methylophaga,Sphingomonas,Litoreibacter and Corynebacterium was correlated with longitude and distance from the coastline.Meanwhile,the bacterial community differences and distributions in the South Atlantic Ocean,the Indian Ocean and the Western Pacific Ocean were mainly influenced by NO3-、K+and Cl-,while air mass transport had no significant effects on bacterial communities in marine bioaerosols in the South Atlantic Ocean,the Indian Ocean and the Western Pacific Ocean.(2)For fungi,there were also significant distance-decay biogeographic distribution patterns of fungal communities in marine aerosols from the central Arctic Ocean,the Canadian Basin,the Chukchi Sea,the Bering Sea,the Okhotsk Sea,and the Northwest Pacific Ocean,and the distance from the coastline had an effect on fungal diversity and species distribution.Basidiomycota were more abundant in marine bioaerosol samples closer to the coastline,and the relative abundance of Cladosporium and Epicoccum were higher in samples closer to the coastline and decreased gradually with increasing distance from the coastline.Air mass transport may be one of the reasons for the differences in fungal communities,and terrestrial air masses have contributed to marine fungal aerosols.In addition to enriching the abundance and diversity of marine fungal aerosols,the long-range input of land-based air masses will bring more Basidiomycota and Cladosporium.Temperature,relative humidity,wind speed,organic carbon,SO42-and Cl-concentrations were the factors that affect the differences in the distribution of fungal communities in marine aerosols.It was therefore hypothesized that the generation of remote atmospheric organic aerosols(characterized by OC)may affect the community structure of microorganisms in marine bioaerosols.3、The contribution of fungal spores to carbon aerosols in marine bioaerosols of the Arctic Ocean and the Northern Pacific Ocean were investigatedFungal spores may affect the physicochemical properties and organic composition of aerosols,and thus the climatic effects of aerosols.A study of fungal spore counts in marine bioaerosols from the central Arctic Ocean,the Canadian Basin,the Chukchi Sea,the Bering Sea,the Okhotsk Sea,and the Northwest Pacific Ocean using tracers of fungal spores found that the concentration of arabinitol was significantly correlated with latitude,with a significant decreasing latitudinal trend,i.e.,relatively high concentrations of arabinitol were observed in marine aerosol samples at relatively low latitudes,and their concentrations became lower with increasing latitudes,and the corresponding fungal spore estimates also had latitudinal differences,and temperature,relative humidity,organic carbon and NH4+ had some effects on the release and distribution of fungal spores in the atmosphere.Combined with the backward trajectories,a significant positive correlation was found between the proportion of terrestrial air masses and the concentration of organic carbon contributed by fungal spores,and fungal spores from terrestrial sources can significantly influence the organic carbon content of oceanic aerosols through long-range transport.More studies are needed in the future to refine the exploration of the spatial and temporal variation of the contribution of fungal aerosols to organic carbon in aerosols.4、The potential ice nucleation activity of marine bioaerosols in the Arctic Ocean and the Northern Pacific Ocean were initially revealed.Atmospheric ice nuclei particles play an important role in cloud precipitation,physicochemical reactions and climatic changes,and therefore it is very necessary to investigate the atmospheric ice nuclei particles.In this study,a high-throughput twoplate ice nucleation assay(TINA)was performed on marine aerosol samples from an Arctic cruise to investigate the presence,composition and potential ice nucleation activity of ice nuclei.The results showed that:(1)The freezing range of ice nuclei in Arctic Ocean and North Pacific Ocean aerosols were between-6.1℃ and-13.7℃,and the accumulated ice nuclei concentration per liter of aerosols were between 10-1 和 10-3 L-1 at-15℃,which indicated that the ice nuclei were heterogeneous in composition,and the ice nuclei concentration showed a more obvious latitudinal distribution difference.After the subsequent heat treatment and filtration experiments,this study found that the ice nuclei in the Arctic and the North Pacific Ocean aerosol samples were smaller than 0.1 μm in size and there were thermosensitive biological ice nucleating particles.(2)At higher temperatures(0℃ to-15℃),the ice nucleating particles in marine bioaerosols were influenced by the carbonaceous fraction of aerosols.In the range of15℃ to-20℃,the ice nucleating particles in marine bioaerosols were mainly associated with marine droplet aerosols and carbonaceous fraction of aerosols,indicating that the sources of ice nucleating particles in marine bioaerosols were complex.The more frequent land-based air mass transport induced the elevated ice nucleation activity of marine aerosols may be an important reason for the latitudinal differences in ice nucleation activity of marine aerosols.In this study,the diversity and spatial distribution of microorganisms and their influencing factors in marine bioaerosols were revealed over a wide range of global waters from mid-and low-latitudes to the south and north poles,and the spatial distribution characteristics and influencing factors of potential ice nucleation activity in bioaerosols from mid-to high-latitudes in the northern hemisphere were explored.The results provide scientific basis and key data for in-depth understanding of the effects of environmental characteristics on the microbial composition of marine aerosols at different latitudes and longitudes and the future impact on climate change. |
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