Green Algae Bloom at Prague Reservoir
- Scientists from the Biological center of the academy of Sciences of the Czech Republic have documented a rare green ice formation in the Lipno Reservoir, a clear sign...
- In 2023, researchers observed patches of green ice on the surface of the lipno Reservoir, located near Lipno nad Vltavou in the Czech Republic.
- "Hydrologists from the Biological Center have mapped this phenomenon in detail, and the green ice at Lipno is one of the best-documented cases worldwide," said spokesperson Daniela Procházková.
green Ice at Lipno Reservoir Reveals Climate and Nutrient Stress
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Scientists from the Biological center of the academy of Sciences of the Czech Republic have documented a rare green ice formation in the Lipno Reservoir, a clear sign of ongoing eutrophication and climate warming in the region.
The Phenomenon
In 2023, researchers observed patches of green ice on the surface of the lipno Reservoir, located near Lipno nad Vltavou in the Czech Republic. The green coloration is caused by the presence of cyanobacteria, specifically the species Woronichinia naegeliana, which normally dominates the reservoir’s waters during summer and autumn.
Scientific Findings
“Hydrologists from the Biological Center have mapped this phenomenon in detail, and the green ice at Lipno is one of the best-documented cases worldwide,” said spokesperson Daniela Procházková. Hydrobiologist Petr Znachor added that the green ice confirms the reservoir’s long‑term eutrophication and the influence of climate warming,noting that ecological changes are occurring even outside the traditional summer season.
Sinicová oka
Zatímco na většině českých přehrad vodní květy sinic s příchodem podzimu postupně mizí a zpravidla se zcela vytrácejí koncem září,Lipno je v tomto ohledu výjimkou.
Dlouhodobá data ukazují, že sinice na lipenské vodní nádrži často převládají až do listopadu a v menším množství se mohou vyskytovat i během prosince a ledna. Zkoumání vědců ukázalo, že v závěru roku 2025 se biomasa sinic držela u hladiny nezvykle dlouho, od podzimu až do zimního zamrznutí nádrže, a to zřejmě díky kombinaci klidného počasí, slabého větru a dlouhé délce slunečního svitu.
Foto: Petr Znachor
Takzvané sinicové oko
„Pod tenkou a místy velmi průhlednou ledovou pokrývkou tak nahromaděné sinice vytvářely nápadné zelené plochy viditelné ze břehu i z leteckých snímků. Nejvíce patrný byl zelený led v období přechodného oteplení okolo Štědrého dne, po opětovném zamrznutí byla zvlášť výrazným rysem takzvaná sinicová oka, tedy místa s čirým ledem nad tmavými shluky sinic, která vznikla rozdílným pohlcováním slunečního záření,“ popsali vědci.
Fenomén podle nich p
Mass Emergence of Caddisflies in Czech River Surprises Scientists and Fishermen
In July 2023, a sudden surge of caddisflies (trichoptera) in the Vltava River near Prague drew the attention of scientists and local fishermen, who reported unusually high numbers of the insects and increased fish catches.
Event Details
Observations began on july 12 when fishermen noted a dense swarm of caddisflies along the riverbank. By July 20, the phenomenon had spread to several kilometers of the Vltava, with insects appearing in large numbers on the water surface and in the surrounding vegetation.
The Czech Academy of Sciences confirmed the sightings and documented the density of caddisflies in the river ecosystem. The event persisted until the end of July,after which heavy snowfall limited light penetration under the ice,marking the likely end of the emergence.
Scientific Response
Researchers from the Czech Academy of Sciences began a study to understand the sudden increase. Preliminary data suggest that changes in water temperature and flow may have created favorable conditions for the insects’ life cycle.
“We are collecting samples and monitoring environmental parameters to determine the drivers behind this event,” said a spokesperson for the Academy.
Impact on Fishing
Fishermen reported higher catch rates during the caddisfly surge, attributing the increase to the insects’ abundance as a food source for fish. Local fishing clubs noted a noticeable rise in trout and pike catches in the affected stretches of the river.
Possible Causes
- Elevated water temperatures due to recent heatwaves.
- Altered river flow patterns affecting larval development.
- Potential influence of climate change on insect life cycles.
Further research is needed to confirm these hypotheses.
Sources: Czech Academy of Sciences – Trichoptera; Novinky.cz – Caddisflies surprise scientists and fishermen
