2023 Volume 59 Issue 2 Pages 27-32
A cyanobacterium Raphidiopsis raciborskii （Wołoszyńska） Aguilera et al., which has not been reported from Lake Biwa, formed a bloom after October 2022 at a pond near the South Basin of Lake Biwa. The identification was confirmed by referring to the sequence of the rbcL gene by BLAST. The density of this species in the surface water reached 7.5×103 trichomes/mL on November 3, 2022. This species has been considered tropical and forms blooms only above 25℃. At this pond, however, it continued to be dominant by December 20 when the water temperature became below 10℃. This species is known to have strains that produce cylindrospermopsin toxic to liver, and saxitoxin that causes paralytic shellfish poisoning. Therefore, it is necessary to confirm the toxicity of this species that occurred in Lake Biwa and its surroundings, and to pay attention to its trends.
