The coefficient of PC as ‘‘the restoration of pH and attached algae’’ is a large positive value in the both models. Morris et al. (1989) have proposed that the communities of benthic macroinvertebrates in acidic conditions showed a tendency to be simple without
herbivorous taxa and this tendency might be due to the lack of attached algae as suitable food for these taxa, which was consistent with our result. Accordingly, the acidification and metal pollution of river environments would not only be inhibiting inhibitions of benthic macroinvertebrates directly but also indirectly due to inhibition of growth of attached algae.