Assessing Short-Term Variability in Seasonal Patterns: Analysis of Chlorophyll-a Dynamics and Environmental Interactions in Lake Mggelsee

Comprehending the dynamics of shallow lakes is vital for effective ecosystem management. Shallow lakes exhibit frequent fluctuations in mixing regime, temperature, and nutrient availability, nurturing a dynamic environment. While numerous studies emphasize the long-term variability within lakes, there is a limited focus on short-term variability. This investigation delves into the relationships, processes, and short-term interactions among chlorophyll-a concentrations and various limnological and meteorological factors throughout the spring, summer, and autumn seasons. A thorough analysis of a high-frequency dataset spanning from April to December 2021 was conducted to explore the driving forces of phytoplankton phenology and dynamics over time. Our study employed Wavelet coherence analysis, a valuable tool in limnological research, to explore relationships between variables at different time scales. This method, assessing correlations between two time series in the time-frequency space, offers a quantitative representation of covariance across various scales and over time. It assists in studying connectivity at a high temporal resolution, identifying synchronization periods, and revealing correlations between signals of diverse types. This analytical approach is essential for unraveling simultaneous processes within complex systems by examining synchronicity across variables and time scales. The study reveals an algal bloom that occurred beneath the ice preceding spring, followed by a clear water phase in spring characterized by a higher respiration process than photosynthesis, indicating a potential influence of top-down control. This points to a dominant biological driver of chlorophyll in spring. Summer featured brief, weak blooms influenced by chemical processes in the lake as a result of prolonged warmth due to global warming, pointing to a combination of physical and chemical drivers. Autumn displayed a uniformly mixed water column, with high coherence between turbidity and wind speed indicating wind-induced resuspension, suggesting meteorological drivers in autumn. Each of these drivers is significant only during specific time intervals, with different processes gaining importance at other times. The analysis in our study was essential in unraveling complex relationships and understanding short-term seasonal variations in environmental variables within a shallow lake. The study underscores the need for a holistic approach to comprehend intricate lake ecosystem dynamics, highlighting the potential impacts of climate change and external factors. This also helped us understand the phenological changes in response to global warming. It enhances our understanding of interactions, time scales, and cyclical patterns, providing insights into short-term dynamics and their impact on the overall ecosystem.