「宇和海沿岸海域の食物網動態―微生物からメソ動物プランクトンまで」

中野伸一

要旨：愛媛県南部の宇和海沿岸海域では、湾外の深層を起源とする冷水塊（底入り潮）と，黒潮を起源とする暖水塊（急潮）が，断続的に流入する。底入り潮は無機栄養塩を豊富に含むため、宇和海の珪藻類を中心とする植物プランクトンの栄養塩供給源として重要と考えられている。対照的に，急潮が流入すると湾内水が一時的に外洋的となり、ピコ植物プランクトンが優占する。このため、底入り潮や急潮が流入すると優占植物プランクトン組成が変化し、これにともない卓越的な物質循環系も変化すると考えられる。本発表では、宇和海沿岸海域における数年間に渡る底入り潮の観測データと各浮遊生物現存量の季節動態から、底入り潮侵入時は珪藻や渦鞭毛藻を主な一次生産者とした生食連鎖が卓越し、急潮侵入時あるいは水温が高まる時期はピコ植物プランクトンや細菌の現存量を起点とした微生物食物網が卓越することを示す。さらに，宇和海の微生物ループの定性・定量的研究の結果のみならず，微生物ループから生食連鎖へのつながりに関する定性・定量的研究の結果の紹介も行う。

(引用文献)

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