First record of Dolichospermum mucosum (Nostocales, Cyanobacteria) in Korea: A study from the Han River

다국어 초록 (Multilingual Abstract)

The heterocytous cyanobacterium Dolichospermum mucosum was observed in Cheongpyeong Lake, located in the mid-to-downstream region of the North Han River. This species is morphologically characterized by irregularly and circularly coiled trichomes, which are consistently surrounded by a transparent mucilaginous envelope at a distance of 19.8±11.3 μm. Akinetes were solitary, nearly spherical, and positioned at a distance from the heterocysts, with a width-to-length ratio of 1.1±0.2. In phylogenetic analyses based on the 16S rRNA and rbcLX genes, this strain clustered within the same clade as previously reported D. mucosum. However, in the phylogenetic analysis, it grouped mostly closely with D. smithii, which exhibited the highest nucleotide sequence similarity. Structural variations in Box-B and V3 helices enabled clear differentiation between D. mucosum and D. smithii. Based on these morphological and phylogenetic characteristics, the Dolichospermum strain was identified as D. mucosum, marking its first recorded occurrence in the Republic of Korea.