Temperature dependence of biofilm metabolism in a lowland stream

Understanding the response of aquatic microbial biofilms to changes in stream water temperature is crucial because temperature directly regulates microbial processes. We investigated the temperature sensitivity of benthic biofilm gross primary production (GPP) and respiration in a lowland stream during 3 seasons with contrasting thermal conditions (winter, spring, summer). We used laboratory-based incubations to estimate metabolic biofilm temperature dependence and applied the Arrhenius equation to estimate activation energy between seasons. As expected, the temperature sensitivity of GPP decreased with increasing in situ temperature conditions (i.e., higher activation energy values in winter and spring compared with summer), suggesting that biofilm GPP rates were more sensitive to temperature change during colder seasons. In contrast, temperature sensitivity of respiration was the lowest in spring, suggesting a limited response to ambient temperature increases and the predominant role of other environmental variables on biofilm temperature sensitivity. Our findings indicate that biofilm metabolic balance is inconsistent with seasonal temperature changes and underscore the importance of considering other environmental variables that influence aquatic microbial biofilm responses to warming.