Original paper

Heterogeneity of benthic diatom communities in different spatial scales and current velocities in a turbid river

Soininen, Janne


Benthic diatoms were sampled in a single rapid in a turbid South-Finnish river in order to study spatial heterogeneity of diatom communities. Diatoms were sampled in separate squares a) with similar current velocities, b) with current velocity gradient and c) with velocity gradient and visible mat of filamentous green algae on stones. Detrended Correspondence Analysis (DCA) indicated that communities differed rather clearly between the sample squares in all sampling designs. Variation between parallel samples was notably smaller. Multi-Response Permutation Procedures (MRPP) showed that communities at separate sampling squares differed significantly from each other. Differences between the diatom communities at separate sampling squares were almost the same magnitude with or without the velocity gradient. MRPP indicated that current velocity (10-125cm s-1) did not have particularly strong effects on diatom distribution patterns. However, in DCA, first ordination axes were probably somewhat connected with current velocity. Values of Pollution Sensitivity Index (IPS) differed significantly between the sampling squares. The dominant diatom species of the study were e.g. Achnanthes minutissima, Melosira varians, Navicula cryptocephala and N. lanceolata. Abundances of a few species, e.g. Diatoma vulgare and Fragilaria arcus, were concentrated on high current velocity according to Indicator Species Analysis.


diatomsriverscurrent velocityheterogeneitymulti-response permutationprocedures.