EXAMINATION OF ENVIRONMENTAL FACTORS AFFECTING THE OVERGROWTH OF EGERIA DENSA IN THE FIRST CLASS RIVERS OF CHUGOKU DISTRICT AT MULTIPLE RIVER BASINS

Abstract

 Effects of Egeria densa on aquatic ecosystems are major concerns in Japan. It is important to efficiently monitor the distribution and abundances of E. densa at large spatial scale and examine the factors affecting the abundance of the species and manage the overgrowth of the invasive aquatic macrophyte in riverine systems. Using environmental DNA(eDNA) analyses, we examined the distribution and abundance of E. densa and the factors that could affect the overgrowth of the target species in the five river basins in Western Japan. Our results indicated that the abundance of E. densa varied among the river basins, and the riverbed slope and low water temperature time were significantly and negatively related to the eDNA of E. densa in the study areas. Our results also indicated that the relationships between the eDNA concentrations and environmental factors varied among the river basins.