We studied the winter to spring transition in Third Sister Lake (TSL), a small glacial lake in southeastern Michigan, to determine the effect of mixing regime on nutrient dynamics and community structure in an urban temperate lake. After ice-off, the oxycline was mixed downward from 3 to 6 m depth, resulting in addition of 5 mg m P-SRP, 857 mg m N-NH4 , and 400 mg m N-NO3 to the epilimnion, but trapping 299 mg m P-SRP, 7877 mg m N-NH4 and 36 mg m N-NO3 in the bottom waters. Nutrients supplied by snow melt runoff (138 mg m P-SRP, 430 mg m N-NH4 , 596 mg m N-NO3 ) were an order of magnitude greater than rain event loads (0.13 mg m P-SRP, 0.17 mg m N-NH4 , and 1.05 mg m N-NO3 ) during the transition time from ice cover to open water. Reduced spring mixing did not have a large impact on N:P molar ratios, because external N:P ratios were low (7.5) compensating for reduced supply of P from the bottom waters. Bacterial production was greater in the hypolimnion than in the epilimnion, and mesocosm experiments showed that bacteria were P limited in the epilimnion but not in the hypolimnion. Total algal and zooplankton densities increased after ice-out, while Daphnia and Bosmina densities decreased. Increases in zooplankton grazing rates after ice-off were most dramatic in small-bodied zooplankton. Sediment core analysis showed that Asterionella relative abundance continues to increase, suggesting that the lake has become more brackish and oligotrophic. Our findings suggest that TSL has undergone a transition from dimictic to meromictic conditions, and that continued salt inputs have altered the structure and function of this ecosystem.