The occurrence of a Euglena pascheri and Lepocinclis ovum bloom in an oxbow lake in southern Poland under extreme environmental conditions

Euglena pascheri is not an abundant species in water habitats, with no previous reports of bloom formation for this species. In 2005, we observed a spring bloom of E. pascheri with Lepocinclis ovum as a subdominant species in a shallow oxbow lake located within the Niepołomice Forest of southern Poland. Rapid increases in the populations of both species were accompanied with low pH values, oxygen deficits, and high concentrations of nitrogen compounds, chlorides, Fe, Mn, Zn, and Cd, but with low concentrations of easily assimilated orthophosphates. Water properties within the habitat were extremely different during and after the bloom. E. pascheri and L. ovum have not previously been considered as index species of any specific water condition or environmental requirements. However, according to our observations, they are organisms tolerant to water acidification, increased salinity, and the presence of heavy metals.