ABSTRACT

Yatsu Higata is one of the most significant remaining tidal flats in Japan. In recent years, Yatsu Higata has witnessed an extraordinary growth of Ulva sp. algae. This paper explores the possible origins of Ulva sp. in Tokyo Bay and describes field studies intended to explore the relationship between the Ulva sp. found in Yatsu Higata and in Tokyo Bay. As a result, the Ulva sp. flourishes in Yatsu Higata, due to the ready supply of nutrient runoff supplied by the Yatsu River. The movement of Ulva sp. from the flats to beyond may help reduce the pollutant load on Tokyo Bay while simultaneously helping to preserve the Yatsu Higata environment.

INTRODUCTION

In addition to serving as a habitat for a wide range of organisms, a tidal flat purifies water runoff and serves as a waterfront buffer. Since the loss of tidal flats and wetlands often results in damage to aquatic environments, the preservation and restoration of such wetlands are major environmental issues throughout the world. In Tokyo Bay, an estimated 90 percent of the original tidal flats has been destroyed or lost to land reclamation projects, making it even more crucial to preserve what tidal flats remain. Registered under the Ramsar Convention in 1993, Yatsu Higata is one of the most significant remaining tidal flats in Japan. It is located a heavily urbanized area near Tokyo, one of the world''s most densely populated cities. In recent years, Tokyo Bay has witnessed an extraordinary growth of Ulva sp. This growth has driven numerous benthic organisms such as Ruditapes philippinarum and Neanthes japonica to the brink of extinction. Furthermore, the area occupied by Ulva sp. continues to expand everys year, raising the prospect that the algae will eventually blanket the entire tidal flat.

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