Cyanobacteria and Algae in Clouds and Rain in the Area of puy de Dôme, Central France

Abstract

The atmosphere contains diverse living microbes, of which the heterotrophic community has been the most studied. Microbes with other trophic modes, such as photoautotrophy, have received much less attention. Here, culture-independent and dependent methods were used to examine the presence and diversity of oxygenic photoautotrophic microbes in clouds and rain collected at or around puy de Dôme Mountain, central France. Cloud water was collected from the summit of puy de Dôme (1465 m above sea level (a.s.l.)) for cultivation and metagenomic analysis. Cyanobacteria, diatoms, green algae, and other oxygenic photoautotrophs were found to be recurrent members of clouds, while green algae affiliated with the Chlorellaceae were successfully cultured from three different clouds. Additionally, rain samples were collected below the mountain from Opme meteorological station (680 m, a.s.l.). The abundance of chlorophyll-a containing cells and the diversity of cyanobacteria and green algae in rain were assessed by flow cytometry and amplicon sequencing. The corresponding downward flux of chlorophyll-a containing organisms to the ground, entering surface ecosystems with rain, varied with time and was estimated between ∼1 and >300 cells cm-2 day-1 during the sampling period. Besides abundant pollen from Pinales and Rosales, cyanobacteria of the Chroococcidiopsidales and green algae of the Trebouxiales were dominant in rain samples. Certain members of these taxa are known to be ubiquitous and stress-tolerant and could use the atmosphere for dispersal. Overall, our results indicate that the atmosphere carries diverse, viable oxygenic photoautotrophic microbes and acts as a dispersal vector for this microbial guild. IMPORTANCE: Information regarding the diversity and abundance of oxygenic photoautotrophs in the atmosphere is limited. More information from diverse locations is needed. These airborne organisms could have important impacts upon atmospheric processes and on the ecosystems they enter after deposition. Oxygenic photoautotrophic microbes are integral to ecosystem functioning and some have the potential to affect human health. A better understanding of the diversity and the movements of these aeolian dispersed organisms is needed to understand their ecology, as well as how they could affect ecosystems and human health.

Airborne microalgal and cyanobacterial diversity and composition during rain events in the southern Baltic Sea region

“…Among the genre of green microalgae, Chlorella sp. was often observed by Dillon et al 47 . Regardless of being in aerosols or rainwater, cyanobacteria and green algae have been found to be the dominant organisms 8 , 47 .…”

“…was often observed by Dillon et al 47 . Regardless of being in aerosols or rainwater, cyanobacteria and green algae have been found to be the dominant organisms 8 , 47 . Similar conclusions can be drawn from the results of the present study.…”

“…Analyzing global trends, only cyanobacteria have been found in the atmosphere of every region of the world 31 . However, according to Dillon et al 47 , cyanobacteria have been detected in clouds at variable abundances between ~ 1% and 50% of the total microbial community. Xu et al 48 found that cyanobacteria constituted only 1.1% of the total bacterial community in clouds.…”

“…However, research on how these organisms are removed with precipitation from the atmosphere is still lacking. To the best of our knowledge, only Dillon et al 47 have reported on the number of microorganism taxa present in rain. Green algae of Trebouxiophyceae and cyanobacteria of Xenococcaceae were predominant in rainwater samples taken at the Opme meteorological station in France 47 .…”

“…To the best of our knowledge, only Dillon et al 47 have reported on the number of microorganism taxa present in rain. Green algae of Trebouxiophyceae and cyanobacteria of Xenococcaceae were predominant in rainwater samples taken at the Opme meteorological station in France 47 . The authors classified the cyanobacteria in their rainwater samples as Phormidiaceae, Rivulariaceae, and Nostocaceae and the orders Pseudanabaenales and Synechococcales.…”