Cladocera and their seasonal changes in the pools of the Ozegahara mire

Abstract

Cladoceran fauna were studied in four pools in the Kamitashiro of the Ozegahara mire from May 2018 to November 2019. Eight species belonging to eight genera were identified in the samples collected. Diaphanosoma brachyurum was widely distributed widely in the pools in the Kamitashiro. The species appearing between the pools were highly similar, suggesting the possibility that the eggs of Cladocera had been resting, but were diffused by snowmelt floods. The appearance time and population density of Cladocera vary greatly depending on the pool, and the annual variation is large, suggesting that the pools in the Ozegahara mire is an unstable environment. Some of the pools, which are thought to have been invaded by fish owing to the flood, had extremely low population densities of Cladocera. This was potentially due to the invasion of the pool by fish, which would have a devastating effect on Cladocera.