Microbial ecology of the South Atlantic Subtropical Gyre: A state-of-the-art review of an understudied ocean region

Abstract

Understanding the dynamics of microbial plankton communities, their metabolic processes and taxonomic composition in oligotrophic ocean basins has been one of the central tasks of contemporary marine microbial ecology and one of the main challenges in a changing global ocean. However, despite its ecological importance, the South Atlantic Subtropical Gyre (SASG) remains poorly understood in relation to marine microbes, which comprise the major drivers of biogeochemical cycles and the largest carbon sink to the deep ocean. This review presents the state of the art of microbial ecology in the SASG, including the adjacent oligotrophic region, the Southwest Atlantic Ocean (SWAO). We have also addressed the theoretical and methodological trends in this field since 1970s, focusing on the main milestones that led to the more-detailed current knowledge of the role of oligotrophic gyres in the global carbon cycle. Finally, we discussed the general patterns of microbial community composition in the SASG, focusing on their potential responses to environmental factors. In spite of increasing efforts to investigate this region, SASG is among the least known oceanic provinces, which has hampered the debate over whether the oligotrophic ocean acts as a sink or source of CO2 into the atmosphere.