Diminished Water Purification Capacity of Tidal Areas Covered by Ulva sp.

摘要

Yatsu Higata is one of the most significant remaining tidal flats in Japan. The site is located in the inner region of Tokyo Bay and was registered as a Ramsar Convention site in 1993. Tokyo is one of the world's most densely populated cities and the water within the bay is eutrophic. In recent years, there has been an extraordinary increase in the growth of Ulva sp. within the tidal flat, which has resulted in numerous benthic organisms, such as clams and lugworm, becoming almost locally extinct. Furthermore, the area colonized by Ulva sp. continues to expand each year, raising the prospect that the algae will eventually blanket the entire tidal flat. This paper explores the environmental characteristics of a tidal flat area covered with Ulva sp. through field studies and a genetic analysis.