Hygiena 2025, 70(1):27-30 | DOI: 10.21101/hygiena.a1876

Extraordinary event at the Seč valley reservoir caused by massive growth of Dinoflagellates

Jana Kratochvílová¹, Jitka Seidlová², Jaroslav Říha³

¹ Krajská hygienická stanice Pardubického kraje se sídlem v Pardubicích, Územní pracoviště Chrudim, Odbor hygieny obecné a komunální, Česká republika

² Krajská hygienická stanice Pardubického kraje se sídlem v Pardubicích, Územní pracoviště Ústí nad Orlicí, Odbor hygieny obecné a komunální, Česká republika

³ Krajská hygienická stanice Pardubického kraje se sídlem v Pardubicích, Územní pracoviště Chrudim, emeritní pracovník, Česká republika

The Seč valley reservoir serves as a retention area during floods, as a source of drinking water and in recent decades as an important recreational area. Due to eutrophication, cyanobacterial blooms have repeatedly occurred here. In July 2024, a highly exceptional event occurred when, after heavy rains, an extreme amount of protozoa from the group of giant nematodes (Dinophyta) entered the reservoir. They then formed a coating that progressed with the flow of water through the reservoir. The phenomenon was observed for about a month. So far, freshwater Dinoflagellates (as opposed to marine Dinoflagellates) have not been found to produce toxins dangerous to the human body, so there has been no direct threat to the health of bathers. Nor has the production of drinking water from the reservoir been compromised.

Keywords: algae bloom, Dinoflagellates, recreation waters - quality, public heath - protection

Received: January 2024; Accepted: March 24, 2024; Published: April 29, 2025  Show citation