Organic biogeochemistry in the oxygen-deficient ocean: A review

Oceanic oxygen-deficient zones (ODZs) encompass open ocean and coastal oxygen minimum zones and euxinic marine basins. A primary goal of this review is to demonstrate how new approaches involving lipidomics and genomics are informing how we think about ODZs. There are five parts to the review. First, a brief overview of early investigations of organic geochemistry in ODZs sets the stage for follow-on work. Second, linkages between organic biomarkers and microbial and geochemical processes are described for three key biogeochemical processes that are characteristic of ODZs: (i) oxidation of ammonium by archaea and anammox bacteria; (ii) redox cycles of metals and sulfur; (iii) the methane cycle. Third, three different approaches are presented that make possible comprehensive, integrated views of the biogeochemistry of the Black Sea, as a case study. Fourth, examples of organic biogeochemical results for ODZs in the modern ocean are projected back into the geological past to show that the same processes have been in play for eons. The final section summarizes how chemistry and biology have been combined in investigations in ODZs and concludes with some challenges for future research. (C) 2020 Elsevier Ltd. All rights reserved.