2013 Volume 7 Pages 39-45
Submerged plant communities in Lake Izunuma-Uchinuma have declined drastically in past 30 years and only isolated populations are observed now. In the past we investigated the submerged plant populations based on boat surveys but this method does not fit the present rarefied situation of submerged plants. In 2011 and 2012 we conducted careful exploratory investigations by foot. Because we already confirmed the presence of at least two stable communities of submerged plants in the lake, we concentrated our investigation efforts there. We found five species of submerged plants(Myriophyllum spicatum L., Cabomba caroliniana A. Gray, Utricularia australis R. Br., Najas oguraensis Miki, and Hydrilla verticillata (L.f.) Royle) and three species (M. spicatum, C. caroliniana, and U. australis) were found in the investigations of both years. From the comparisons of observed shoot numbers between the results of both years, the numbers in 2012 were greater than those in 2011. Especially in C. caroliniana, a rapid increase was recorded in both investigation points and now C. caroliniana is the most common submerged plant in Lake Izunuma.
