Abstract
This study was investigated to obtain some basic information for the influence of Tsunami associated with the Great East Japan Earthquake on the structural succession of the Hasunuma seaside park pond ecosystem located in Kujyukurihama coastal line in Chiba prefecture. This pond was under the eutrophicated state of hyper P loading, and Aoko of Anabaena spiroides was occurred in every summer season. For insecurity and complaint from citizen, sun exposure of sediment of this eutrophicated pond was conducted in 2004, 2009 and 2010. In spite of this attempt, Aoko was occurred again in summer and red tide of Cryptomonas spp. was observed in winter, and eutrophication of this pond was in progressed more. Furthermore, Tsunami with the Great East Japan Earthquake in 2011 made a drastic change of ecosystem structure of this pond, that is, the water quality was improved and Ruppia maritima which is endangered spices water plant has become observed. The biodiversity became rich with increase of zooplankton and the food web became complexified.
