Viable resting cysts in surface sediments of the Paldang Reservoir System in Korea

Abstract

In order to understand the mechanism of freshwater algal blooms, this study investigated the quantification and identification of the resting cysts. For this study sediment samples were collected in Paldang Reservoir system (Paldang Reservoir, Kyeongan Stream, Pukhan River and Namhan River) from July 2009 to June 2010. This is the first study of its kind conducted in Korean freshwaters. Viable resting cysts were induced to excysts and identification was based on characteristics of both resting cyst and vegetative stages. Almost all of the resting cysts disintegrated within one week under conditions for germination. Thirty-seven morphotypes of resting cysts were encountered, of these thirty-one species were identified, representing 21 genera. This study revealed resting cysts of the potentially toxic species Anabaena sp., Cylindrospermum stagnale, Glenodinium sp., Peridiniopsis spp., Peridinium sp.,and Woloszynskia sp., and resting cysts of bloom-forming species Cryptomonas ovata, Chlamydomonas spp., Eudorina spp., Pandorina morum and Volvox spp.. In addition, Bracteacoccus sp., Chlorosarcina sp., Chlorococcum sp., Golenkinia spp., Oogamochlamys sp., Polyedriopsis spinulosa, Spirogyra spp. and Euglena spp. were also identified in this study. Among them, eight species as vegetative stages have not previously been reported from water column in Paldang Reservoir. The resting cyst abundances ranged from 42 to 260 cells g− 1 from July 2009 to June 2010. The highest abundance was recorded in May 2010 and the lowest in September 2009. The presence of these diverse resting cysts in Paldang Reservoir system could indicate a potential seedbed for the initiation of blooms and toxic events.