Nonlinear water clarity trends and impacts on littoral area in Minnesota lakes

Lake water clarity is an indicator of quality, trophic status, and habitat condition. Changes in impact lake ecosystems may reflect land use changes or presence invasive species. Quantifying temporal can be challenging because varies seasonally, annually, spatially within among lakes. We developed a hierarchical generalized additive model to quantify trends (Secchi depth) from 1979 2018 for 909 Minnesota lakes, accounting seasonal spatial variability. Water increased by 0.41 m across lakes 1984 1988 2014 2018. Lake-specific varied: did not change significantly 59.0% 34.5% decreased 6.5% dynamics caused considerable variability littoral area between seasons years. Our results have wide applications aquatic ecology, including understanding food webs, assessing fish habitat, evaluating impacts