September 2014 and March 2015 at the three sites (PD-1, PD-2 and PD-3) of Lake Paldang. Nitrogen and phosphorus concentrations were higher at PD-2 than at PD-1 and PD-3. TSI (TN) values at the three field sites were in the range of 65~85, which were the level of eutrophic or hypereutrophic state. TSI (TP) also showed high values (49~68), which were the level of mesotrophic or eutrophic state. Akinete germination potential was higher at PD-2 with increased nutrient (nitrogen and phosphorus), and algal growth potential also increased with nutrient enrichment.

Akinete germination may be a starting point of some akinete-producing cyanobacterial blooms in eutrophic freshwater systems. This study examined germinability of akinete of a cyanobacterium Anabaena circinalis isolated from the sediment of the North Han River (Cheongpyung Dam), Korea, under several environmental factors such as temperature (5∼25℃), light (0∼100μmol photons m-2 s-1), nutrients (nitrogen and phosphorus) and pH (5~12). The high germination rate appeared at high temperature: >55% at 25℃, followed by 15% at 15℃, 10℃ and 10% at 5℃. Low light intensity was favorable for akinete germination. Over 45% of germination occurred at low light intensities (5, 15 and 30μmol photons m-2 s-1), while less than 10% of germination occurred at both 50 and 100μmol photons m-2 s-1. No germination occurred in the dark condition. Akinete germination rate increased with nutrient (phosphorus and nitrogen) enrichment, and nitrogen addition showed greater effect on the germination compared to phosphorus addition. Akinetes germinated well at neutral or slightly alkaline pH condition (pH 7 and pH 8: >55%), but no germination was observed at pH 11~12. The present study demonstrates some favorable ambient conditions of Anabaena circinalis germination, which could provide useful information to study the germination conditions of other Anabaena species or akinete-forming algae and predict its bloom in eutrophic freshwaters.

남조류는 겨울철에 휴면포자의 형태로 퇴적층에서 존재하다가 적합한 환경조건이 되었을 때 다시 영양세포로 전환된다. 이렇게 전환된 영양세포는 성장에 적합한 환경이 되었을 때 대량증식 하게 되어 수체 내에서 우점한다. 이전까지의 국내 대부분의 연구는 수체 내 영양세포의 변동과 환경인자와의 관계 또는 영양세포에 대한 생리생태적 연구부분에 국한되었다. 하지만, 휴면포자에서 영양세포로 진행되는 부분에 대한 연구가 조류대량증식의 궁극적인 기작이 되므로 휴면포자에 대한 연구는 조류의 생활사를 이해하는 데에도 매우 중요하다. 또한 다른 조류들간의 변동 및 천이의 연구를 위해서도 필수적이다.