International
and national protection strategies and directives focus mainly on
macroscopic organism and attempt to maintain their endangered habitats.
However, microscopic communities are also threatened by decreasing
biodiversity and many species including freshwater algae can disappear
without even knowing they were present in the habitat. Defining rarity
of microscopic taxa is not easy. The species’ rarity is based on
detailed knowledge of distribution and abundance of species. But only
limited information is available about rare algal species especially in a
given ecoregion. Reducing the data gaps, here, we present altogether 20
phytoplankton taxa rare in Hungary: three species of
Chlorophyceae, eight species of
Trebouxiophyceae, two taxa of
Euglenophyceae, one-one species of Cyanobacteria,
Bacillariophyceae and
Mediophyceae and three species of
Xanthophyceae. One of them, the
Cylindrotheca gracilis
is on the Hungarian Red List. Physical and ecological characteristics
of standing waters where these species were found as well as their
former occurrence all over the world are also reviewed.
