Propagation of filamentous green alga Klebsormidium (Klebsormidiophyceae) community at a inorganic acidic spring in southern part of Mt. Ontake

Abstract

　Morphological characteristics, biomass, and habitat conditions of a filamentous green alga, Klebsormidium, propagated in spring water with pH values 2.9–3.6 located in the volcanic inorganic acidified stream of the Nigorisawa River in southern part of Mt. Ontake, were investigated six times between 2016 and 2019. The Klebsormidium species formed long and unbranched filamentous colonies comprising > 1000 cells, which did not fragment easily. Width, length, and length-to-width ratio of vegetative cells ranged between 5.8–8.2 μm, 10.7–14.4 μm, and 1.4–2.3, respectively. H-pieces were not observed at the cellular junctions. Empty zoosporangia cells were marked by indistinct pores. The species was identified as K. flaccidum, the type species of the Klebsormidium genus, based on cell morphology. The spring water, in which K. flaccidum propagated, was the underground water of the Nigorisawa River, formed owing to the construction of a check dam. The species probably grew by active photosynthesis using dissolved inorganic carbon accumulated by volcanic activity, respiration, and geological location.