Abstract
We gathered basic information relevant to the conservation of the aquatic macrophytes remaining in Lake Kasumigaura and its watershed. We studied macrophyte distribution and determined the environmental factors controlling their distribution in a canal with steep banks. The canal was one of the few locations hosting Potamogeton crispus L. However, some invasive species were also noted. The P. crispus community was characterized by a higher-than-average current velocity and a low nitrogen level. Recently, eutrophication and aversion have markedly decreased the canal habitat for suitable submerged plants. The free-floating plant communities were characterized by high total- and PO_4-phosphorus levels; most were in paddies. Many alien plant communities had colonized land associated with private dwellings and a carp farm. Neighboring land uses influenced the distributions of aquatic plant communities. We found that analysis of species distribution and land uses in the area surrounding the lake was important for conserving the aquatic macrophytes of Lake Kasumigaura.
