Abstract
Though archaea are ubiquitous in the oceans, at times present in quantities equal to bacteria, in general, archaea are underreported when compared with bacteria, and little is known about archaeal connectivity in the ocean. Here, we present the first time series data of size‐fractionated archaea with temporal resolution of days across a depth transect in the oligotrophic Atlantic Ocean. Archaeal communities were variable from day to day, both in regards to community composition and relative abundance. In the context of the total prokaryotic community, we found that water depth and particle size were both determinants of the archaeal share of microbial populations, though the archaeal portion of the community was less discriminating between size and depth classes than the rest of the community. Quantitative PCR shows lower relative abundances of archaea in the deep Atlantic Ocean than previously reported. Overall, we find far lower connectivity between depths in the Atlantic Ocean than suggested by previous studies.