Making temporal dynamics relevant: The role of macrophytes in the phenological complexity of a shallow freshwater lake

A multidisciplinary approach demonstrates how submerged macrophytes generate high phenological variability in Hungary's Lake Balaton. A 239-month time series of water chlorophyll indices derived from Landsat 7 imagery from 1999 to 2019 was used. These data facilitated the generation of area-based phenological patterns, which allowed an assessment of phenological variability by correlating chlorophyll index sequences with spatially adjacent values. The results showed that phenological variability was consistently low (below 5%) at the farthest points from the shore, indicating uniform phenological processes in the pelagic zone of Lake Balaton. Conversely, the littoral zone showed almost eight times higher variability, indicating increased diversity in shallow water areas. In particular, extensive macrophyte biomass datasets revealed a direct relationship between increased phenological variability in the littoral zone and macrophyte biomass (Spearman rank correlation: 0.893). This research highlights contrasting phenological patterns between phytoplankton and macrophyte communities, driven by different life cycles, and the possibility of effectively using satellite data to delineate phenological separation within lakes.