Redox-Controlled Ammonium Storage and Overturn in Ediacaran Oceans

As a key nutrient, nitrogen can limit primary productivity and carbon cycle dynamics, but also evolutionary progress. Given strong redox-dependency of its molecular speciation, environmental conditions control localization bioavailability. This particularly applies to periods in Earth history with frequent redox fluctuations, such as the Neoproterozoic. We here report on chlorophyll-derived porphyrins maleimides Ediacaran sediments from Oman. Exceptionally light δ 15 N values (< –10‰) derived anoxygenic phototrophs point towards ammonium assimilation at chemocline, whereas isotopic offset between kerogens chlorophyll-derivatives indicates variable regime cyanobacterial eukaryotic production surface waters. Biomarker maleimide mass balance considerations imply shallow euxinia during terminal stronger contribution productivity, possibly consequence nutrient ‘lockup’ large anoxic reservoir. Synchronous 13 C anomalies Ediacaran–Cambrian boundary may reflect one series overturn events, mixing isotopically-light DIC into oxic By modulating access nitrogen, have periodically affected perturbations, played role timing metazoan radiation across early Cambrian.