A simple model for predicting oxygen depletion in lakes under climate change

The advent of climate change has placed aquatic ecosystems at risk for potential declines in water quality, including an increase in the number of lakes experiencing substantial dissolved oxygen (O2) depletion. Through its influence on the thermal structure of lakes via elevated water temperatures and alterations in stratification phenology, climate change intensifies biogeochemical and ecological processes involved in O2 consumption, giving rise to conditions like hypoxia/anoxia. However, predicting O2 dynamics is difficult, with in situ O2 depletion rates showing considerable lake-dependent variability, underpinned by distinct underlying mechanisms. Our study attempts to overcome these lake-specific features and targets distilling key components of O2 depletion into a simple and transferable conceptual model applicable across a diverse array of lakes and at large scales. Using O2 depletion rates from literature reflecting variability in trophic state, we quantified the typical O2 depletion rate ranges for oligotrophic, mesotrophic, and eutrophic lakes and assessed their temperature sensitivity for a broader climate impact assessment. Our model gave reasonable estimates for O2 depletion and risks of anoxia through 3 explanatory variables: trophic state, stratification duration, and hypolimnion temperature. We validated our model predictions using data from 5 German lakes and assessed the relative importance of the 3 influencing factors. This easy-to-use approach has potential for lake management to attain rapid assessments of possible future problems with O2 dynamics in a given lake, even in the absence of in situ data. Moreover, it allows scaling of O2 dynamics continentally/globally without lake-specific hydrological or morphological details.