八甲田山の湧水河川, グダリ沼の水環境と底生動物相

抄録

Water environments and benthic invertebrate fauna were studied in a spring-fed Gudari-numa Stream in Hakkoda Mountains, Aomori Prefecture, northern Japan during 2014–2019. The stream has ever-cool and less organic overlying water and productive bottoms with abundant attached algae. A total of more than 129 species of benthic invertebrates belonging to eleven phyla were recorded from the stream. Along with epigean forms, the benthic fauna contained rich stygobites such as Pseudocrangonyx amphipods, nerillid and lumbriculid annelids along with stygophile forms in the shallow hyporheic zone. The zoobenthic assemblages entirely lacked several groups of animals which are common in neighboring streams, for example, odonates, heptageniids and net-spinning trichopterans, while the community had rich and abundant diamesine and orthocladiine chironomids, and planariid flatworms. The lopsided structure of the zoobenthic community could be related with the strongly localized organic matters to the bottoms as well as ever cool and stable enviroments.