57

浚渫ヘドロを用いた大規模造成干潟の底質と底生生物の特性について

高山 百合子*1・片倉 徳男*1・国分 秀樹*2

著者らは,これまでに浚渫ヘドロを用いた現地干潟造成実験により干潟生態系に最適な底質の有機物量と泥分を定量化した。その成果を基に,三重県英虞湾において約7200m2の大規模干潟を造成し,底質と底生生物の追跡調査を実施した。本報では,大規模干潟の造成前および造成後4年間の調査結果を取りまとめ,底質と底生生物の変化特性について整理した。造成干潟では,浚渫ヘドロが底生生物の餌である底生微細藻類の栄養供給材となり,造成後約1年で底生生物の種類数と個体数が増加し,その後安定して定着することが実証された。さらに,本実験における底質と底生生物の関係から干潟生態系に最適な底質条件の妥当性が確認された。

キーワード:  自然再生,沿岸生態系,生物多様性,浅場

*1 技術センター 土木技術研究所 水域・生物環境研究室
*2 三重県水産研究所

Properties of Sediment and Benthos in Man-made Tidal Flats Mixed with Dredged Sediment

Yuriko TAKAYAMA*1, Norio KATAKURA*1 and Hideki KOKUBU*2

The authors conducted a field experiment in man-made tidal flats and determined the optimum quantitative conditions of the mud and organic matter in the ecological environment of benthos. The results were used to construct a large-scale tidal flat 7,200 m2 in area at Ago Bay, Mie prefecture. The changes in the properties of the sediment and benthos were observed over four years. This paper describes the original conditions of the area and the observation results for the experiment, and discusses the relationship between the bottom sediment and the emergence of the benthic community. The number of species and the benthic population increased in the first year after tidal flat construction and then stabilized, which may mean that the dredged sludge is a source of nutrients for the benthic microalgae in the tidal flats. The relationship between the bottom sediment and the emergence of the benthos confirmed that the optimum sediment conditions for tidal flats, as proposed in previous studies, were appropriate.

Keywords:  nature restoration, coastal ecosystem, bio-diversity, shallow water zone

*1 Hydraulic and Bio Engineering Research Section, Civil Engineering Research Institute, Technology Cente
*2 Mie Prefectural Fisheries Research Institute