Biotic induction and microbial ecological dynamics of Oceanic Anoxic Event 2

Abstract Understanding the causal mechanisms of past marine deoxygenation is critical to predicting long-term Earth systems response climate change. However, processes and events preceding widespread carbon burial coincident with oceanic anoxic remain poorly constrained. Here, we report a comprehensive biomarker inventory enveloping Oceanic Anoxic Event 2 that captures microbial communities spanning epipelagic benthic environments in southern proto-North Atlantic Ocean. We identify an abrupt, sustained increase primary productivity predates by ∼220 ± 4 thousand years, well before other geochemical proxies register biogeochemical perturbations. During event, recurrent photic zone euxinia triggered major reorganization accompanied decrease production. These findings highlight how organic drivers operated along continuum concert ecological changes, antecedent, localized increases production destabilizing cycling promoting progressive leading 2.