Spatial distribution patterns of benthic macroinvertebrate functional feeding groups by stream size and gradient in Republic of Korea

Abstract

Benthic macroinvertebrate functional feeding groups (FFGs) are influenced by the availability of food sources, which can be affected by stream size and gradient. We investigated the spatial distribution patterns of FFGs by stream size (stream order, catchment area and stream width) and gradient (altitude and slope). In addition, we attempted stream classification based on the distribution patterns of FFGs. To achieve these goals, a total of 996 sampling sites of national scale located in the Republic of Korea were investigated from 2008 to 2016. Among the five physical variables, stream width and slope showed linear relationships with the indicator values of FFGs. These two physical variables had larger influences on the distribution of FFGs compared to other variables. Geology (the type of rocks) showed little influences on the distribution of benthic macroinvertebrate communities. We classified streams focusing on catchment (stream size) area and altitude (stream gradient) because they are constants that do not change with disturbances. The FFGs and benthic macroinvertebrate assemblages were distinctly changed by stream types, indicating that the stream classification criterion adequately represented changes in physical variables in biotic terms. In addition, the distribution of FFGs and biotic assemblages showed that benthic macroinvertebrates in the Republic of Korea were more influenced by the altitude (stream gradient) than the catchment area (stream size). In overall, this study found that the stream size and gradient markedly influence the distribution of FFGs in national regions of the Republic of Korea. Further research is needed focusing on the level of microhabitats and other parameters to identify the promising variables that influence biotic distribution.