Variability and regulation of the planktonic respiratory quotient in a eutrophic lake (Lake Vombsjön) in summer 2016

Bacterial respiration and biomass growth are important processes for carbon cycling in freshwater ecosystems and bacterial respiration is often quantified from measured O2 concentrations by using a respiratory quotient (RQ=O2 consumed to produce CO2, in moles) of 1. Recent studies have shown, however, that RQs can vary a lot in different aquatic ecosystems (0.5-5), which may lead to an under- or overestimation of respiration. In this study, we conducted in-situ measurements of O2 and CO2 fluxes in a eutrophic lake (Lake Vombsjön) to assess the magnitude and variability of the RQ and bacterial growth efficiency (BGE) during summer 2016. The RQ was mostly