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積雪中の融解水による藻類粒子の垂直移動
山本, 鎔子;林, 卓志;落合, 正広;福原, 晴夫;野原, 精一;北村, 淳;尾瀬アカシボ研究グループ
Permalink : http://hdl.handle.net/2115/49013
KEYWORDS : 赤雪;尾瀬湿原;粒子の移動メカニズム;Red snow;Oze mire;Movement mechanism of algal particles
Abstract
尾瀬ヶ原湿原および尾瀬沼では毎年5月から6月の融雪期にアカシボと呼ばれる赤雪現象が生じる. 赤雪の原因は, およそ10μmの径をもつ赤褐色の球状の緑藻Hemitoma sp.胞子に起因するもので, この胞子の被壁は酸化鉄が付着し赤褐色を呈している. この胞子は湿原表層部の融雪水の動きに従って積雪下層部から上層部に向かって動くことにより起きると考え, この可能性を検討するために, アクリル製の円筒型コアを用いて実験を行った. 雪を詰めたコア（雪コア）の下層部にアカシボの粒子あるいはアカシボの粒子とほぼ同じ径をもつChlamydomonasを添加し, 積雪下層部に融雪水の存在する現場と融雪水のない現場にそれぞれ埋設し, 一定時間後にアカシボ粒子あるいはChlamydomonasの動きを調べた. 融雪水の存在する地点においてのみ下層部のアカシボ粒子およびChlamydomonasは雪コアの上層部に向かって動くことが観察された. この結果から, 雪コア内の粒子は積雪下層部から雪面に向けて, 融雪水の動きにともなって移動する可能性が高いと結論した.
The red snow phenomenon called ‘Akashibo’is usually observed from May to June during melting snow time in Ozegahara mire in Japan. The striking red coloration was mainly caused by the reddish-brown spherical particles with the diameter of about 10μm that are the spores of a green alga,Hemitoma sp.covered with iron oxide. These spores are enriched at the ground surface below the snow at the beginning,and their enrichment shifts to the upper layer as snow melting proceeds. It was thought that this shift is generated by movements of the spores from the lower layer to the upper layer. To test this possibility,we put acryl tubes containing snow with the spores at the bottom part on the mire at several different sites. Vertical movement of the spores toward the top part was observed only in the tubes which were put on the sites where snow melting water was present underneath the snow. These results support the idea that a flow of snow melting water toward the snow surface caused the movement of the spores from the lower layer to the upper layer.
The red snow phenomenon called ‘Akashibo’is usually observed from May to June during melting snow time in Ozegahara mire in Japan. The striking red coloration was mainly caused by the reddish-brown spherical particles with the diameter of about 10μm that are the spores of a green alga,Hemitoma sp.covered with iron oxide. These spores are enriched at the ground surface below the snow at the beginning,and their enrichment shifts to the upper layer as snow melting proceeds. It was thought that this shift is generated by movements of the spores from the lower layer to the upper layer. To test this possibility,we put acryl tubes containing snow with the spores at the bottom part on the mire at several different sites. Vertical movement of the spores toward the top part was observed only in the tubes which were put on the sites where snow melting water was present underneath the snow. These results support the idea that a flow of snow melting water toward the snow surface caused the movement of the spores from the lower layer to the upper layer.
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