The influence of riparian vegetation on macroinvertebrate community structure in four Hong Kong streams

The benthic macroinvertebrate communities of four Hong Kong streams with similar water chemistry but differing riparian conditions were investigated. Differences in chlorophylls and detritus standing stocks reflected the degree of shading by riparian vegetation; Tai Po Kau Forest Stream (TPKFS) and Bride's Pool (BP) had an allochthonous food base while autochthonous energy sources were relatively more important in Lam Tsuen River (LTR) and Pui O Stream (POS). The macrobenthos was dominated by aquatic insects and morphospecies richness (excluding Chironomidac) ranged from 70 (POS) to 94 (TPKFS). Differences in total macroinvertebrate abundance across sites were not related to chlorophylls or detritus.
Highly significant differences in the morphospecies comprising the most numerous taxa at each site were observed, and TPKS and BP were more similar to each other than to the LTR-POS pair with respect to top-ranked taxa. Intraspecific comparisons of the abundance of these taxa revealed significant differences for 23 out of 30 morphospecies. Multiple regression of the abundance of key morphospecies against independent variables (chlorophylls a , b and c , total chlorophyll and detritus) yielded significant best-fit models for all taxa showing intersite differences in abundance. These data can be interpreted as reflecting the influence of riparian vegetation on stream community structure via an effect on food supply. The results were discussed with reference to the applicability of the River Continuum Concept in the tropics.