Effects of hydrologic seasonality on dissolved organic matter composition, export, and biodegradability in two contrasting streams

Description

Environmental and seasonal processes are important watershed drivers controlling the amount, composition, and fate of dissolved organic matter (DOM) in aquatic ecosystems. We used ten months of water samples and eight months of bioassay incubations from two
contrasting catchments (agriculture and natural, forested) to assess the effects of seasonal variability on the composition, export, and biodegradability of DOM. As expected, the DOM composition and exports were more allochthonous-like and autochthonous-like in
the forest and agriculture streams, respectively. However, we found no relationship between DOM composition and biodegradability in our study, suggesting that broad environmental factors play a large part in determining bioavailability of DOM. We found that both differences between the catchments and seasonal variability in hydrology and water temperature cause shifts in DOM composition that can affect exports and potentially affect its susceptibility to microbial activity. More research is needed to fully understand the impact of land use and temporal variability on bioavailability and delivery to downstream ecosystems.
Author Keywords: Bioavailable dissolved organic carbon, Biodegradability, Dissolved organic matter, Export, Seasonality, Streams