D. Mollenhauer et al., Macroscopic cyanobacteria of the genus Nostoc: a neglected and endangered constituent of European inland aquatic biodiversity, EUR J PHYC, 34(4), 1999, pp. 349-360
Nostoc caeruleum, N. commune, N. microscopicum, N. parmelioides, N. prunifo
rme, N. verrucosum and N, zetterstedtii are air cyanobacteria forming macro
scopically visible colonies. They were selected for a nature conservation c
ase study. Their specific identity is easily determined, and reliable histo
rical records are available. Life conditions for these species in Europe in
the 'virgin' postglacial biosphere, historical reports and the present-day
situation are surveyed. Data concerning type materials, supplements to the
protologues, and morphology are presented. The classic descriptions and di
agnoses based only on herbarium material are supplemented by ontogenetic de
tails. Global/regional changes in the biosphere (climate, regulation of rak
e levers and river flows, import of plant nutrients, water pollution, acidi
fication, etc.) and their consequences for aquatic biocoenoses are reviewed
. The analysis of man-made impacts on the environment enables us to evaluat
e the present state of habitats where these algae occur today or where they
are now extinct. Documented changes in environmental conditions in the pas
t serve as a basis for assessing the likely future developments of the biot
opes and of the whole landscape where these cyanobacteria form part of the
biocoenoses. However, there are few recent detailed ecological studies on b
enthic and terrestrial cyanobacteria. It is not yet clear which of the diff
erent components covered by the comprehensive term 'eutrophication' is the
decisive factor for the changes in aquatic biocoenoses and the decline of c
yanobacterial biodiversity.