Aquatic hyphomycetes of 21 rivers in southern Ireland

Foam was collected from 21 rivers in southern and western Ireland in autumn 1993 and 1994 and early spring 1994, and aquatic hyphomycete spores were enumerated and identified. Sixty-eight aquatic hyphomycete species were identified, with a significantly greater number of species being recorded from rivers with a riparian vegetation of woodland than from rivers with a more herbaceous vegetation. The number of species recorded in this study was comparable to numbers recorded from Europe and North America. However, the mean number of taxa recorded per river (26.5) was comparatively low. Detrended correspondence analysis showed that rivers of contrasting water hardness and conductivity could be differentiated on the basis of differences in the composition of their aquatic hyphomycete spora. Assemblages of associated species were also detected, such as those confined to soft-water rivers. TWINSPAN analysis also distinguished a core assemblage of species that were widely distributed.