Macroinvertebrates of Altai mountain rivers: factors of their formation and features of distribution within altitudinal gradient

Abstract

With an increase in altitude, both abiotic and biotic conditions in mountain watercourses change. To assess the features of spatial distribution of macroinvertebrates as well as to identify the driving factors of this dynamics, the data on species richness, abundance and biomass of EPT taxa (mayfly, stonefly, caddisfly) from 21 small mountain rivers of Altai were analyzed. By location, all rivers were divided into 4 groups: the ones running in the low-mountain (<1000 m asl) zone, in the low (1000–1500) and upper (1500–2000) parts of the middle mountains and in the high-mountain (>2000 m asl) zone. A total of 71 EPT macroinvertebrate taxa were recorded in the studied streams. Species richness (according to the average species number per sample) as well as abundance and biomass of macroinvertebrates decreased with an increase in altitude. The maximum variance in structural indicators of communities appeared due to the combined influence of the location of the altitudinal zone and phytoplankton development level (estimated by the content of chlorophyll a). At the same time, categorical predictors (both abiotic and biotic) included in the analysis better explained the variability of diversity-related indicators than that of abundance and biomass. When developing the environmental monitoring programs for mountain watercourses, the identified trends in reduction (with altitude) of species richness of macroinvertebrate taxa responsible for the formation of taxonomically poor and strongly vulnerable communities in high-altitude areas should be taken into account.