Resolving the Drivers of Algal Nutrient Limitation from Boreal to Arctic Lakes and Streams

Abstract Nutrient inputs to northern freshwaters are changing, potentially altering aquatic ecosystem functioning through effects on primary producers. Yet, while producer growth is sensitive nutrient supply, it also constrained by a suite of other factors, including light and temperature, which may play varying roles across stream lake habitats. Here, we use bioassay results from 89 lakes streams spanning boreal Arctic Sweden test for differences in limitation status algal biomass along gradients colored dissolved organic carbon (DOC), water concentrations, ask whether there distinct patterns drivers between Single nitrogen (N) or N-limitation with secondary phosphorus (P) was the most common condition lakes. Average response N-addition doubling biomass; however, degree modulated physical chemical conditions versus regions. Overall, responses were strongest at sites low background concentrations inorganic N. Low temperatures added nutrients but had weaker streams. Further, DOC mediated addition differently among Stream dampened higher DOC, whereas increased moderate depressed high DOC. Our suggest that future changes availability, particularly N, will exert strong trophic state freshwaters. However, highlight important factors shape availability different parts networks, ultimately affect integrated systems ongoing environmental changes.