Diverse microbial communities have now been described in clouds, air, and fog, giving us the first glimpses at the controls and variability of bacterial and fungal dispersal. However, less consideration has been given to the implications of this highly heterogeneous bacterial and fungal movement for ecosystem function (e.g. decomposition, plant growth). Central to this topic is an understanding of where taxa in aerial communities originate and how they colonize terrestrial habitats (if at all). We took advantage of a simple, pristine, desert system in the Namib Desert, Namibia, to examine whether microbes in marine-derived fog play a role in plant mutualisms or decomposition of desert grasses. We sampled aerial (fog, ocean spray, air) and terrestrial (litter, soil, grass endophytes) microbial communities in fog-prevalent and fog-rare areas of the dune sea of the Namib Desert using sequencing- and isolate-based methods. We also sampled the ocean and ocean spray, where advective fog originates.
Results/Conclusions
We found that fungal and bacterial communities in fog were temporally variable, and contained signatures of both soils and ocean communities, even far (50km) from the coast. Up to 20% of these fog taxa were present and active in decomposing plant litter, and in living plants as fungal endophytes, suggesting these taxa are relevant to desert functions. However, fog taxa were not more abundant in terrestrial areas that received more fog deposition. Measurements on fungal isolates suggest that physiological plasticity (specifically salt tolerance range) could help marine microbes in fog to colonize and function in the desert environment. In sum, we found fog contains microbes that contribute to terrestrial function, but did not find evidence that the distribution of fog limits the dispersal of entire decomposer taxa. In contrast, the ubiquity of microbial generalists with high physiological plasticity may facilitate their wide dispersal by enabling colonization and function in novel habitats.