<p>We study a nonlinear mathematical model describing the relation between microbial populations and nutrient availability in glacial environments. The model incorporates both nutrient and microorganism supply terms, together with an energy-dependent factor, reflecting periodic environmental influences such as melting and irradiation. We first analyze the autonomous case (i.e., time-independent energy factor and supplies) and provide sufficient conditions for the existence and stability of equilibrium points, including a critical threshold for nutrient accumulation that leads to qualitative changes in microbial dynamics. We also identify a pseudo-bifurcation phenomenon, where equilibria leave the biologically relevant domain without undergoing a classical bifurcation. In the non-autonomous case, we prove the existence of periodic solutions using topological degree theory and continuation methods. Numerical simulations confirm the theoretical results and illustrate distinct dynamical regimes depending on seasonal averages of the input parameters. In particular, we show that under certain conditions, microbial populations can persist with periodic oscillations, while nutrients either stabilize or accumulate over time. These results highlight how nutrient supply thresholds, influenced by melting-driven inputs, play a key role in controlling microbial abundance and nutrient cycling. This work provides a theoretical foundation for understanding microbial responses to seasonal environmental forcing in glacial and polar ecosystems.</p>