原著論文　ORIGINAL PAPER

大気暴露による河川の不快糸状緑藻類コントロール

福嶋　悟^１・３），皆川　朋子^２）

１) 横浜市環境化学研究所　〒235-0012　神奈川県横浜市磯子区滝頭１−２−１５
２） (独)土木研究所自然共生研究センター　〒501-6021　岐阜県各務原市川島笠田町官有地無番地

Satoshi FUKUSHIMA^1･3) and Tomoko MINAGAWA²⁾: Controls of nuisance filamentous green algae in rivers with atmospheric. Ecol. Civil. Eng. 11(2), 123-132, 2008.

1) Yokohama Environmental Research Institute, 1-2-15 Takigashira, Isogo-ku, Yokohama, 235-0012, Japan
2) Aqua Restoration Center, Public works Research Institute, Mubanchi, Kanyushim Kasada, Kawashima, Kagamigahara-city, Gifu, 501-6021, Japan

Abstract: To show effective measures against filamentous green algae that grow in abundance in regulated rivers, in-situ experiments on the effects of atmospheric exposure were carried out using communities of Spirogyra sp. and Cladophora sp. as subjects. In addition, the changes in biomass attributable to atmospheric exposure and discharge were compared. Morphological changes of the chloroplast occurred in most cells of Spirogyra sp. and Cladophora sp. with atmospheric exposure. The biomass of Spiroogyra sp. communities decreased by about 90-98% in cases of one-day atmospheric exposure, three-day exposure, and discharge after three-day exposure. The latter case exhibited the greatest biomass decrease. It was the only case in which the ash free dry mass decreased. The biomass of Cladophora sp. communities decreased by 84 % in both cases of discharge after one-day atmospheric exposure and three-day atmospheric exposure. In those cases, the ash free dry mass also decreased markedly after atmospheric exposure. Although the relative abundance of filaments of Cladophora sp. accounted for about 80% of the conmmunities before atmospheric exposure, the relative abundance of other algae increased more than 75 % after atmospheric exposure. Both filamentous green-algal communities were abundant after discharge, however they were decreased markedly by atmospheric exposure, suggesting that atmospheric exposure is an effective method for control of filamentous green algae in regulated rivers.

Key words: atmospheric exposure, control, discharge, green algae, regulated river

摘要

ダム下流河川で大量に発生する糸状緑藻類の対策に有効な方法を明らかにすることを目的として,大気暴露の効果についてSpyrogyra sp.群集とCladophora sp.を対象に検討した．さらに,大規模な出水が両糸状緑藻群集の現存量に及ぼす影響についても検討した．その結果,以下の知見が得られた．
1)Spyrogyra sp.とCladophora sp.の多くの細胞で，大気暴露後に葉緑体の形態的な変化が見られた．
2)Spyrogyra sp.群集では，1日と3日間大気暴露の3ケースの実験で現存量は約 90〜98%減少し，3日間の大気暴露後に出水があったケースで現存量は最も小さくなった．有機物量は大気暴露後に出水があったケースでのみ減少した．
3)Cladophora sp.群集では 1日大気暴露後に出水があったケースと3日間大気暴露したケースで共に，現存量は84%減少し，有機物量も大気暴露後に明瞭に減少した．大気暴露前の群集ではCladophora sp.の糸状体が約80%を占めていたが，暴露後には他の藻類が約75%以上を占めるようになった．
4)大気暴露した両糸状緑藻群集の現存量は明瞭に小さくなったのに対して，大規模な出水後でも両群集の現存量は大きく，ダム下流河川の糸状緑藻類対策に大気暴露が有効な方法であることが示された．

2007年1月18日受付，2008年5月10日受理
1) e-mail: sa01-fukushima@city.yokohama.jp