A Microbial Survey of Lake Kivu: Mechanisms of Nitrogen Cycling

Abstract

Ocean Anoxic Events (OAEs) are periods in Earth’s history during which large por-tions of the oceans contain decreased amounts of oxygen. OAEs can be very difficult to study since modern oceans are generally well-oxygenated. Here Lake Kivu, a meromictic lake with deep anoxic layers, is presented as a potential OAE analogue and is used to study a proposed nitrogen cycling mechanism that could explain the characteristic 𝛿¹⁵N excursions associated with OAEs. Biomarkers are isolated from sediment samples and analyzed across depth below the lake floor. The results are consistent with a biologically mediated nitrogen cycling mechanism, shedding more light on a potential mechanism to explain nitrogen cycling in OAEs.