Like many bodies of water, Lake Lipno is no stranger to cyanobacteria. Cyanobacteria blooms are notoriously foul-smelling, but the real issue is the damage they wreak on local ecologies. It’s unclear how frozen algae blooms could affect their ecosystems. However, Lake Lipno has long experienced longer algae seasons. “Green ice on Lake Lipno fits into the long-term changes we observe here in connection with eutrophication and ongoing climate change,” said hydrobiologist Petr Znachor.