This session highlights ways in which data from national lake assessments and longer-term national data sets are being used by researchers and policy-makers. In the United States, the National Lakes Assessment (NLA) is a statistical survey of the condition of our nation's lakes, ponds, and reservoirs. It is designed to provide information on the extent of lakes that support healthy biological condition and recreation, estimate how widespread major stressors are that impact lake quality, and provide insight into whether lakes nationwide are getting cleaner. The U.S. Environmental Protection Agency’s NLA is also being used by researchers to improve understanding of lake ecology. With an emphasis on evaluating effects of environmental stressors on lake health, NLA datasets from 2007, 2012, and 2017 support national and regional analyses of environmental trends such as changes in lake trophic status, ecological impacts of chloride contamination, and comparisons of drivers and spatial structure of biotic and abiotic properties of lake, wetland, and stream ecosystems. Comparisons of NLA results and longer-term in situ data sets with remote sensing observations of large lakes and reservoirs in the U.S. raise new questions among limnologists and lake managers. In Canada, researchers have embarked on similar lake assessment projects. The NSERC Canadian Lake Pulse Network is a scientific initiative focused on environmental issues affecting Canadian lakes. It brings together experts in lake science, spatial modelling, analytical chemistry, public health, and remote sensing, amongst others. The impacts of land-use changes, climate change, and contaminants are assessed while developing new tools for lake stewardship. In The Netherlands, researchers are using long-term monitoring data with ecosystem models to investigate mechanisms behind the decline of target species for biodiversity conservation as well as to simulate the effect of potential restoration measures on food web functioning.