Sarah Evans, Michigan State University biologist and co-lead author of a study in the journal Science of the Total Environment, worked with a team of scientists to provide the first view of fog as a vector for microbes, or the means for microbial transfer over long distances into new environments.
Evans’ research with co-lead author Elias Dueker of Bard College, and co-author Kathleen Weathers, a senior scientist at the Cary Institute of Ecosystem Studies, compared fog microbial communities in two very different, fog-dominated ecosystems: Coastal Maine, whose geography is conducive to the creation of marine aerosols and frequent fog formation; and the Namib Desert, a hyperarid coastal fog desert on the west coast of southern Africa.
The team analyzed air samples—both foggy and clear—and rain, filtered to capture bacterial cells at each site, to record the variety and abundance of micro-organisms present. In Maine, data were collected within 30 meters of the ocean during two field campaigns. In the Namib Desert, data were collected at two sites about 50 kilometers away from the coast.
"Fog droplets were found to be an effective medium for microbial sustenance and transport,” said Evans, an assistant professor who holds joint appointments in the Departments of Integrative Biology and Microbiology and Molecular Genetics, and is an MSU Kellogg Biological Station faculty member. “At both sites, microbial diversity was higher during and after foggy conditions when compared to clear conditions."
Moisture in fog allows microbes to persist longer than they would in dry aerosols. As a result, fog deposits a greater abundance and diversity of microbes onto the land than deposition by air alone.
"When fog rolls in, it can shift the composition of terrestrial airborne microbial communities,” Dueker said. “And in a fascinating twist, on the journey from the ocean to the land, microbes not only survive, but change during transport. Fog itself is a novel, living ecosystem."
The authors noted that there are also possible health implications for the marine-terrestrial fog connection. Fog at both sites contained pathogenic microbes, including suspected plant pathogens and species known to cause respiratory infections in immune-compromised people. This raises concern about the role that fog could play in transporting harmful microbes.
"We need a better understanding of fog's role as a vector for microbes, with special attention to pathogens that threaten health," Weathers said. "Warming sea surface temperatures and altered wind regimes are likely to affect fog distribution in many coastal regions."
The team identified the need for future studies that help predict which microbes are most likely to be transported and deposited by fog. Using traits like spore size and behavior, models could be developed that help forecast harmful fog.
“These findings underscore the potential for fog to serve as an important and understudied mechanism of microbial dispersal and ecosystem connections between the land and sea,” Evans said. “Its patterns and functional implications from these systems can serve as a foundation for future work in fog biology and its role in terrestrial ecosystem dynamics.”
Robert Logan, a microbial ecologist with the MSU Kellogg Biological Station, also participated in the study.