Data supporting: Green ice in a eutrophic reservoir: a late-season manifestation of cyanobacterial bloom persistence

This dataset supports the manuscript “Green ice in a eutrophic reservoir: a late-season manifestation of cyanobacterial bloom persistence”. It contains (1) seasonal monitoring data from the Frymburk profile in Lipno Reservoir, including chlorophyll-a, nutrient concentrations, major phytoplankton-group biovolumes, and Woronichinia naegeliana biovolume; (2) daily near-surface water temperature, air temperature, and reservoir water-level elevation from the dam area; and (3) Sentinel-2-derived chlorophyll-a summary statistics processed with RWQForecast, including the quality-screening flags used for seasonal comparison. The data document persistence of a Woronichinia-dominated late-season bloom into December 2025 and provide environmental and remote-sensing context for the subsequent green-ice event. See the accompanying README and workbook Metadata sheet for variable definitions, provenance, quality-control rules, and interpretation notes.