Title : Nitrogen fluxes and primary productivity in Archaean Ocean

Abstract

The most oxidised form of nitrogen - Nitrate (NO3⁻) - serves as an essential and often limiting nutrient for life in the modern well-oxygenated ocean. However, ~3 billion years ago (Archean eon) the Earth’s surface environment and oceans were largely deprived of oxygen. Nitrogen isotopic composition (δ¹⁵N) of sedimentary rocks of that time suggests ammonium (NH4+) dependent anaerobic nitrogen cycling. In an attempt to quantify nitrogen fluxes and productivity in such ammonium-based ecosystem, we have developed a numerical two-box model that simulates Archean nitrogen cycling under ammonium-dependent conditions. In this seminar I will be discussing the results of the model and evaluate the Archean nitrogen isotopic record.