Calleja, M. L. | Search bioRxiv

bioRxiv2026

Latitudinal diversity gradients and selective microbialexchange at the Atlantic ocean-air interface

Microbial communities at the ocean-atmosphere interface play a vital role in nutrient, aerosol, and water cycling, yet their large-scale biogeography remains scarcely studied. Here we assessed microbial cell abundance and community structure in air and surface ocean samples along a 14,400 km transect from the polar circle to the equator. Air and surface ocean microbiomes were taxonomically distinct across the North East Atlantic. The microbiome in the air had a lower local community richness compared to the surface ocean, yet was more diverse across larger geographical scales. Our results suggest that terrestrial-derived air masses affected air and surface ocean communities. Air microbial communities showed a latitudinal diversity gradient with richness and cell abundance increasing from the polar circle to the equator. We observed an exchange of microbial lineages between ocean and air, however, most lineages were confined to one realm, suggesting lineage-selective aerosolization and deposition of microbial cells.

microbiology↗

bioRxiv2019

Dissolved organic matter and heterotrophic prokaryotes diel patterns reveal enhanced growth at the mesopelagic fish layer during daytime

Contrary to epipelagic waters, where biogeochemical processes closely follow the light and dark periods, little is known about diel cycles in the oceans mesopelagic realm. Here, we monitored the dynamics of dissolved organic matter (DOM) and planktonic heterotrophic prokaryotes every 2 h for one day at 0 and 550 m (a depth occupied by vertically migrating fish during light hours) in oligotrophic waters of the central Red Sea. We additionally performed predator-free seawater incubations of samples collected from the same site both at midnight and at noon. Comparable in situ variability in microbial biomass and dissolved organic carbon concentration suggests a diel supply of fresh DOM in both layers. The presence of fish in the mesopelagic zone during daytime promoted a sustained, longer growth of larger prokaryotic cells. The specific growth rates were consistently higher in the noon experiments from both depths (surface: 0.34 vs. 0.18 d-1, mesopelagic: 0.16 vs. 0.09 d-1). Heterotrophic bacteria and archaea in the mesopelagic fish layer were also more efficient at converting DOM into new biomass. These results suggest that the oceans twilight zone receives a consistent diurnal supply of labile DOM from diel vertical migrating fishes, enabling an unexpectedly active community of heterotrophic prokaryotes.

ecology↗