STRUCTURE OF MACROZOOBENTHOS COMMUNITIES AND THEIR BIOMASS DYNAMICS IN THE OLA RIVER, NORTHERN COAST OF THE SEA OF OKHOTSK, MAGADAN REGION

摘要

The structural organization of macrozoobenthos communities is analyzed in the epirhitral, the upper, middle and lower metarhitral and the hyporhitral of the Ola River flowing into the northern coast of the Sea of Okhotsk, Magadan Region. Dominant taxa, typical species and, in some cases, indicator species are determined for every community. The Ephemeroptera: Ameletus sp. and Cinigmula sp. are observed to belong to the taxa characteristic of all three communities revealed in the Ola River's metarhitral, playing important roles in their structure. Both species composition dynamics and macrozoobenthos biomass are shown to be linked to peculiarities of the hydrological regime of the river located in the conditions of interrupted and insular permafrost distribution. At the same time, the between-year aspect of the species composition reveals some stability of the complex of dominant taxa. The spatial distribution of the biomass conforms to basics of the River Continuum Concept, its highest values being registered in the metarhitral community (2.0-4.8 g/m(2)). Variations in biomass dynamics is high enough, decreasing downstream, with the lowest registered in the lower metarhitral community. The dynamics of between-year variation in biomass shows two peaks of growth confined to the summer and winter periods. The key factor defining the predominance of one of the two is considered to lie in peculiarities of the life cycles of aquatic insects which fowl the basis of the structure of communities.