Abstract
Oxygen minimum zones (OMZs) have substantial effects on the global ecology and biogeochemical processes of marine microbes. However, the diversity and activity of OMZ microbes and their trophic interactions are only starting to be documented, especially in regard to the potential roles of viruses and protists. OMZs have expanded over the past 60 years and are predicted to expand due to anthropogenic climate change, furthering the need to understand these regions. This review summarizes the current knowledge of OMZ formation, the biotic and abiotic factors involved in OMZ expansion, and the microbial ecology of OMZs, emphasizing the importance of bacteria, archaea, viruses, and protists. We describe the recognized roles of OMZ microbes in carbon, nitrogen, and sulfur cycling, the potential of viruses in altering host metabolisms involved in these cycles, and the control of microbial populations by grazers and viruses. Further, we highlight the microbial community composition and roles of these organisms in oxic and anoxic depths within the water column and how these differences potentially inform how microbial communities will respond to deoxygenation. Additionally, the current literature on the alteration of microbial communities by other key climate change parameters such as temperature and pH are considered regarding how OMZ microbes might respond to these pressures. Finally, we discuss what knowledge gaps are present in understanding OMZ microbial communities and propose directions that will begin to close these gaps.
Highlights
Microbial Ecology of Oxygen Minimum Zones Amidst Ocean DeoxygenationThe diversity and activity of Oxygen minimum zones (OMZs) microbes and their trophic interactions are only starting to be documented, especially in regard to the potential roles of viruses and protists
In addition to rising temperatures and ocean acidification, deoxygenation is one of the key effects of climate change on marine ecosystems
In all three of these sampling sites, the Oxygen minimum zones (OMZs) contained unique communities compared to the other sampling depths. This trend of differing bacterial communities within OMZs compared to more oxygenated depths has been observed in other sampling sites within the ETSP (Beman and Carolan, 2013), as well as other OMZs such as the ETNP (Faull et al, 2020), the Bay of Bengal (Rajpathak et al, 2018; Fernandes et al, 2019, 2020; Lincy and Manohar, 2020), the Arabian Sea (Bandekar et al, 2018a; Fernandes et al, 2020), the Cariaco Basin (Zinger et al, 2011), and the Black Sea (Zinger et al, 2011). These findings suggest that dispersal may only add to species richness in OMZs when the species in question can persist in lowered oxygen conditions
Summary
The diversity and activity of OMZ microbes and their trophic interactions are only starting to be documented, especially in regard to the potential roles of viruses and protists. This review summarizes the current knowledge of OMZ formation, the biotic and abiotic factors involved in OMZ expansion, and the microbial ecology of OMZs, emphasizing the importance of bacteria, archaea, viruses, and protists. We describe the recognized roles of OMZ microbes in carbon, nitrogen, and sulfur cycling, the potential of viruses in altering host metabolisms involved in these cycles, and the control of microbial populations by grazers and viruses. The current literature on the alteration of microbial communities by other key climate change parameters such as temperature and pH are considered regarding how OMZ microbes might respond to these pressures.
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