This study was carried out to elucidate the development of unprecedented water-bloom caused by a single species of colonial green algae Eudorina elegans in the upstream area of the Seungchon weir located in the Yeongsan River from late April to May 2013. The Yeongsan River is typically regulated system and the waterbody is seriously enriched by both external and internal sources of nutrients. Seasonal algal outbreaks were highly probable due to various potential factors, such as the excessive nutrients contained in treated wastewater, slow current, high irradiation and temperature, in diatom (winter), green algae (spring) and bluegreen algae (summer). Spring green-tide was attributed to E. elegans with level up to 1,000 mg m-3 (>50×104 cells mL-1). The bloom was exploded in the initial period of the algal development and after then gradually diminished with transporting to the downstream by the intermittent rainfall, resulting in rapid expansion of the distribution range. Although the pulsed-flows by the weir manipulation was applied to control algal bloom, they were not the countermeasures to solve the underlying problem, but rather there still was a remaining problem related to the impact of pulsed-flows on the downstream. The green-tide of E. elegans in this particular region of the Yeongsan River revealed the blooming characteristics of a colonial motile microalga, and fate of vanishing away by the succeeding episodic events of mesoscale rainfall. We believe that the results of the present study contribute to limno-ecological understanding of the green-tide caused by blue-green algae in the four major rivers, Korea.

한반도 동해안에 분포하는 대표적인 석호중의 하나인 화진포호에서 2010년 봄철(4~6월)에 돌말 Skeletonema costatum가 대발생하였다. 본 연구는 대발생기와 소멸기 동안 저수지의 식물플랑크톤 군집의 특성을 파악하고 수 질을 근거로 하는 호수의 영양지수를 산출하여 수질을 평가하였다. 분석결과 국내에서 가장 높은 세포밀도(¤105 cells mL-1)를 보였으며, 수온은 20􀆆C 전후였으나 더 높았 던 여름철(7월 이후)에는 소멸하였다. 저수지의 수질은 높은 염분도, BOD, COD, 인산염, 낮은 N/P비, 투명도 등 으로 부영양~과영양 상태로 나타났다. 식물플랑크톤 군 집은 돌말류가 높은 세포밀도를 보인 조류발생기 동안에 는 높은 우점도와 낮은 다양도를 보였으며, 소멸기에는 다시 회복되는 특성을 나타냈다. 결국 2010년 화진포호 의 Skeletonema costatum 대발생은 봄철 가뭄이 장기간 진행되고 하천수의 유입이 감소함으로써 비롯된 것으로 판단되며 매년 반복될 가능성을 시사해 주었다.