Daily dissolved oxygen saturation patterns mediated by light and stream discharge in littoral regions of an oligotrophic mountain lake

Abstract

Nearshore regions of lakes span ecosystem boundaries—terrestrial–aquatic, lotic–lentic, littoral–pelagic—and integrate signals that propagate across these boundaries, yet these regions are undersampled relative to pelagic waters. To examine controls on littoral ecosystem function, we measured high-frequency dissolved oxygen data along the shore of a large, oligotrophic lake during 2 years. We identified two distinct diel oxygen patterns—one whose peak was synchronous with solar noon and another whose peak lagged solar noon—that were distinguished as well by their overall magnitude of dissolved oxygen. We found that these diel oxygen patterns were correlated most strongly with daily light availability when sensors were deployed along a depth gradient and with stream discharge when sensors were in locations close to or far from inflowing streams. These results show that nearshore dissolved oxygen responds variably to climate and physical conditions, that is, light and discharge, depending on the location along the shore. Our approach further highlights the need to apply diverse quantitative methods to develop a better understanding of variability in littoral lake productivity in response to changing environmental conditions, particularly in oligotrophic lakes with low productivity signals that are typically challenging to detect.