Phosphorus (P) is generally available in short supply relative to biological demand in terrestrial and aquatic ecosystems globally. However, humans have altered the global P cycle, mobilizing significant quantities of geological P reserves. A similar pattern with the global nitrogen (N) cycle has increased its availability in these ecosystems as well. Because N has an atmospheric component in its cycle, evidence has suggested that diazotrophy can cause P limitation to evolve at the ecosystem scale and that this process may be common in lakes and reservoirs. However, the time scale(s) and underlying biogeochemical phenomenon driving this evolution remains poorly understood. Here, we present a long-term data set with short-term fertilization experiments and metatranscriptome data to examine the effects of an annually recurring seasonal nitrate drawdown on phytoplankton biomass, gene expression, and nutrient limitation in a man-made, mesotrophic lake. A 30-year record in this lake demonstrates a pattern of nitrate drawdown during the summer and an increase during late winter into early spring. We hypothesize that increased water temperature leads to nitrate immobilization in the food web resulting in seasonal transitions from P-limitation in spring to N-limitation in summer accompanied by a shift from upregulation of N accumulation to N consumption genes. To test this hypothesis, we conducted monthly sampling events across the temporal drawdown gradient. Initial water samples and bioassays were analyzed for carbon (C), N, P, and chlorophyll-a to assess temporal variability in nutrients related to phytoplankton biomass and transcriptional activity. Initial results suggest P-limitation occurred in April and May and switched to strict N & P co-limitation in June through October. We also observed expression of genes associated with N transport, assimilation, and metabolism that vary temporally. If our hypothesis is supported, the experiments provide compelling evidence for a pattern of perpetual N-limitation across decades in this lake.