Resting stages of freshwater algae from surface sediments in Paldang Dam Lake, Korea

Abstract

Although the studies on marine cysts are quite frequent, information on resting stages of freshwater algae are rather scarce. The present study focused on the identification of resting-stage algae from freshwater sediments in Paldang Dam Lake, an important source of water for South Korea. We examined the morphological characteristics of resting-stage specimens and identified them by germination experiments or DNA analysis. Surface sediment samples were collected from 12 sites in Paldang Dam Lake from July 2009 to June 2010. Thirty-five resting stage morphotypes were identified: 19 chlorophytes, 6 dinoflagellates, 5 diatoms, 2 cyanobacteria, 2 euglenoids and 1 cryptophyte. Resting-stage and vegetative cells of five chlorophyte morphotypes could not be identified by morphology. These specimens were identified by molecular sequence analysis based on the nuclear-encoded SSU rDNA sequences of Polyedriopsis, Oogamochlamys and Chlamydomonas. Our samples included resting-stage of the potentially toxic species Cylindrospennum stagnale, the first recorded sighting in Korea. Resting-stage assemblages were dominated by diatoms, which ranged from 560 to 2750 cells g(-1). Resting-stage of diatoms and cyanobacteria were abundant along the eastern shore toward the southern part of Paldang Dam Lake, where there have been periodic algal blooms.