Epiphytic Zoobenthos on Bryophyte Mats in a Cool Mountain Stream, Toyamazawa

Abstract

Quantitative samples of benthic macroinvertebrates were taken in November 1989, May and September 1990 from the mats of bryophyte (Rhynchostegium riparioides) and bare rock bottom at upper reaches of a cool mountain stream, Toyamazawa in Nikko National Park, central Japan. Numbers of taxa confirmed by the study were low, 11-13 and 13-14 on bryophyte mats and bare rock bottom, respectively. The overall abundance of macroinvertebrates in bryophyte areas was much higher than that in bare rock areas. Micrasema sp. MC was the most abundant taxon on bryophyte mats, and the density on the mats exceeded 100, 000 individuals m^-2 in November 1989. The abundance of Micrasema sp. MC on bryophyte mats was 2.8-16.3 times higher than that on bare rock bottom. The second and the final instar larvae of Micrasema sp. MC on the mats were significantly more abundant than those at bare rock bottom on almost all sampling occasions.