| dc.description.abstract | Relationships between soft-bodied benthic algae and their habitat have traditionally been studied among different waterbodies, but less attention has been paid to the effects of combined microenvironmental conditions within streams. Soft-bodied benthic algae are considered as good indicators for both trophic and acidification status in Norwegian rivers, but the way microenvironment might influence ecological assessments when using algae have not been investigated yet. Benthic algae and environmental factors from 32 locations along a Norwegian oligotrophic river were analysed in order to 1) explore relationships among important abiotic environmental variables in the river, 2) study changes in biovolume, algal richness and associations among soft-bodied algae in relation to microenvironment, and 3) investigate the effects of environment on ecological indices based on soft-bodied algae at meso- and microhabitat scales. Mesoscale variations in water quality along the river continuum did not influence the ecological indices. Deep and still-water microenvironments were associated to higher resulting values for the periphyton index of trophic status (PIT) and lower values for the acidification index of periphyton (AIP). Algal richness was better predicted by photosynthetic active radiation (PAR), while the combination of PAR and water velocity was suggested in order to explain variations in relative biovolume. Multivariate analyses showed relationships between algal species and different measured microenvironmental variables. The insights from this study suggest that registering microenvironmental factors during benthic algal assessments may be valuable for future improvements of the trophic and acidification indices used in Norway with regard to the EU Water Framework Directive. | nb_NO |
