The Relative Role of Nutrient Inputs, Climate, Land Use, and Spatial Patterns on Chlorophyll a Concentrations Worldwide

Water quality degradation is one of the largest threats to freshwater ecosystems, and understanding how multiple drivers such as nutrients, climate, morphology, and land use impact water quality is of high interest because it will help mitigate the potential consequences of degraded waters. We used chlorophyll a as a proxy to primary production to quantify: 1) the relative importance of drivers on water quality in freshwater lakes globally, and 2) identify the spatial patterns and signatures of chlorophyll and its drivers in freshwater lakes across the US. We found that total phosphorus (TP) inputs at the local spatial scale was the single most influential driver of chlorophyll levels in freshwater lakes globally and in the US. Climate, including warmer temperatures, increased solar radiation inputs, and wetter conditions, further contributed to elevated chlorophyll concentrations. As such, we suggest management efforts should continue to focus on drivers acting at local spatial scales, in particular TP, to mitigate primary production in lakes worldwide.