A new paper is published in Water Resources Research by Anna Störiko who was a visiting PhD student in ERG in 2019. The paper is co-authored by Philippe and Adrian Mellage, formerly a PhD student in ERG. The paper presents a reactive transport model that can simultaneously predict the rates, functional-gene transcripts, and enzymes of denitrification. The goal is to quantitatively relate the transcripts and enzyme concentrations to the actual rates of denitrification and, hence, nitrate consumption, under dynamic environmental conditions, for example variations in dissolved oxygen levels. The model is applied to a virtual case where a nitrate-rich groundwater interacts with a nearby river under stable and fluctuating conditions. The simulations yield complex and nonunique relationships between the denitrification rates and the molecular-biological variables. A key observation is that functional-gene transcripts respond to daily fluctuations of environmental conditions, while enzyme and genes concentrations remain stable over such time scales.