Temporal changes and vertical distribution of macrophytes in Lake Kawaguchi

The distribution of macrophytes in Lake Kawaguchi, Japan, was surveyed in August 1999 using a sampling anchor from a boat. The survey revealed that the present aquatic vegetation was composed of 17 submerged species, and no floating-leaved plants were present. The diversity of submerged plants and their vertical growth limits decreased progressively from the west to the east end of the lake. At the time of the survey, the dominant species was Elodea nuttallii (Planch.) St. John, which had once grown explosively in the mid-1980s in the lake, and except for Vallisneria asiatica Miki, all of the species commonly observed in the lake seem to have diminished their growth greatly. Among them, Potamogeton compressus L., which was the most dominant species in the lake before the invasion of Elodea nuttallii, had decreased most severely. It is suggested that the present state of aquatic vegetation in this lake was much influenced by the persistent growth of Elodea nuttallii as well as by environmental factors.