Influence of Streamside Surface Area on Aquatic Biota and Biofilm Activity

Abstract

In this study, fillers (gravel and brick) of different surface areas were installed on both banks of two test channels so as to have the same capacity, and effects of differences in surface area and porosity of the streamside on aquatic biota and activity of the attached biofilm were investigated at downstream distance. The results showed that an increase in surface area and porosity causes change in the composition of microbial community, increasing the number of total bacteria and nitrifying bacteria and improving oxygen uptake activity. Although there was no evident difference found in the biofilm microfauna between the two test channels, a result was obtained that oxygen uptake rate by protozoa and metazoa evaluated by laboratory batch experiments quadruples farther downstream in the gravel-filled channel. Furthermore, it was clear, from the result that there observed many Physidae and Ephemeroptera that prey on deposits such as detritus precipitated in the interstices, that the amount and diversity of macrobenthos increased in the gravel-filled channel. These results suggest that surface area and porosity are extremely important factors in the detritus food chain constructed by settling and accumulation of particulate organic matter, and it is considered that controlling them can create a diverse aquatic biota.