A SIMPLE METHOD FOR ASSESMENT OF COLONIZATION RISK OF A LARGE FILAMENTOUS ALGAE Cladophora glomerata AT DAM DOWNSTREAM REACHES USING BED MATERIAL SIZE DISTRIBUTION DATA

Abstract

 The large filamentous algae Cladophora glomerata often grows on coarse and stabilized (armoring) riverbeds. However, the habitat environment of the algae has been poorly understood. In this study, we investigated the effect of riverbed environment especially bed material size distribution on occurrence of the algae for building a simple assessment method of its colonization risk. A relationship between river environment variables and presence/absence data of the algae at the up and downstream reaches of the Koshido Dam in the Yahagi River, Japan was modelled with logistic regression analysis. It showed that the occurrence of the algae was mainly explained by only the valuables of riverbed material in this study, suggesting that the risk of the algae could be evaluated by the riverbed material size.