<p>Paired measures of dissolved oxygen (O₂) and carbon dioxide (CO₂) provide critical insights to ecosystem metabolism. While a 1:-1 stoichiometry is often presumed between the coupled processes of photosynthesis and respiration, many other physical, chemical, and biological processes decouple dissolved O₂ and CO₂ concentrations in lakes. Tracking departures from 1:-1 stoichiometry may provide insights into more integrative ecosystem functioning, particularly during fall when temperatures change and destratification occurs in temperate climates. Using continuous measures of both dissolved O₂ and CO₂ in a small temperate headwater lake, we looked at the interannual gas departure signals during fall over 7&#xa0;years. The beginning of fall, defined here as the start of leaf colour change, differed among years but coincided well with the onset of lake destratification and a shift in surface gas concentrations. Fall surface CO₂ accumulation rates varied considerably, whereas O₂ depletion rates were rather similar among years. Departure signals were broadly related to interannual differences in temperature and precipitation: more CO₂ accumulated in surface water during the hottest-wettest fall compared to the coldest-driest one (0.81 and 0.37&#xa0;µmol L⁻¹ d⁻¹, respectively), presumably from more catchment inputs, whereas lower surface CO₂ accumulation occurred during years with prolonged hypolimnetic hypoxia. Other internal biological and chemical phenomena potentially influenced fall departure signals, including a large metalimnetic oxygen peak, higher fall surface primary production, and methane oxidation among others. We suggest gas departures during fall provide an integrative metabolic fingerprint for temperate stratified lakes, including catchment connectivity and internal processing.</p>