亜寒帯汽水湖(風蓮湖)におけるシジミ漁業の再構築を見据えた水質・底質環境の現状評価
辻, 泰世;門谷, 茂
Permalink : http://hdl.handle.net/2115/61060
JaLCDOI : 10.14943/lowtemsci.74.21
KEYWORDS : 河口域;人為負荷;植物プランクトン;底生微細藻類;底質;ヤマトシジミ
Abstract
本研究では2011 年から2013 年にわたり風蓮湖と流入河川の水質・底質調査を実施した.河川水由来の高濃度の栄養塩が塩分15~20 における植物プランクトンの活発な増殖(Chl.a 年中央値:3.3~13μg/L,Chl.a 現存量:~130 mg/m2)を支え,表層堆積物Chl.a 現存量が豊富である(~950 mg/m2)といった特徴も観測された.故に,ヤマトシジミの生産に対し微細藻類が良質な餌資源として機能すると考察された.一方,現在の底質環境は底生動物の生息を脅かす状態であった.各年,表層堆積物中の平均TOC が33~39±25~31 S.D.mg/g に及び,特に河口付近においてAVS-S は2.5 mg/g を上回る傾向があった.河川負荷がもたらす底質環境の悪化改善がヤマトシジミ漁業再構築の要であると考察された.
We had monitored water and sediment properties of a brackish lake in subarctic zone (Lake Furen, Japan) from 2011 through 2013. In mesohaline water (salinity: 15~ 20), phytoplankton proliferated vigorously (annual median Chl.a:3.3~13 μg/L, Chl.a standing stock: ~130 mg/m2), with rich nutrients loaded thorough rivers. As for surface sediment, we ascertained Chl.a standing stock to be markedly rich (~950 mg/m2). Phytoplankton and microphytobenthos are considered to act as effective food source for Corbicula japonica. On the other hand, sediment condition remained harmful to benthos. Annual average TOC content reached 33~39±25~31 S.D.mg/g, with AVS-S being more than 2.5 mg/g, especially near river mouth. We concluded that physicochemical properties of surface sediment, formed by allochthonous inputs, should be improved toward the reconstruction of Corbicula japonica fishery.
We had monitored water and sediment properties of a brackish lake in subarctic zone (Lake Furen, Japan) from 2011 through 2013. In mesohaline water (salinity: 15~ 20), phytoplankton proliferated vigorously (annual median Chl.a:3.3~13 μg/L, Chl.a standing stock: ~130 mg/m2), with rich nutrients loaded thorough rivers. As for surface sediment, we ascertained Chl.a standing stock to be markedly rich (~950 mg/m2). Phytoplankton and microphytobenthos are considered to act as effective food source for Corbicula japonica. On the other hand, sediment condition remained harmful to benthos. Annual average TOC content reached 33~39±25~31 S.D.mg/g, with AVS-S being more than 2.5 mg/g, especially near river mouth. We concluded that physicochemical properties of surface sediment, formed by allochthonous inputs, should be improved toward the reconstruction of Corbicula japonica fishery.
FULL TEXT:PDF