Distribution and Seasonal Growth of the Invasive Diatom Cymbella janischii in Tamagawa River System

Abstract

The degradation of ecosystem services in rivers due to the invasion and expansion of invasive attached diatoms, Cymbella janischii, is a grave concern. The distribution and seasonal growth of C. janischii in the Tamagawa River system were studied. In the upstream area of the Tamagawa River, C. janischii formed visually identifiable clusters resembling “dirty cotton balls”. C. janischii was identified only under a microscope in the midstream area, but was not observed in the downstream area, and differences were observed between water areas. C. janischii was also distributed in a branch river that joined the upper midstream area of the Tamagawa River, but its concentration was negligible. In the upstream area of the Tamagawa River, C. janischii formed clusters from April to May. During this C. janischii bloom period, the water temperature in the upstream area of the Tamagawa River coincided well with the temperature of the rivers in which C. janischii grows in North America.