Macroinvertebrates reveal environmental gradients: methods and method development in the Ob River basin

Abstract

The Ob is the seventh longest river in the world and its length (including the largest tributary Irtysh) is 5410 km. The huge size of the Ob River catchment and diverse natural resources of the region give rise to numerous anthropogenic factors affecting aquatic ecosystems. The patterns of longitudinal changes in the composition aquatic communities are still uncertain, especially for large rivers. To assess the role of environmental factors in the structure of communities, we analyzed longitudinal changes in the species richness, abundance, and biomass of macroinvertebrate communities along a 3363-km section of the Ob River. The trends of longitudinal changes in macroinvertebrate communities differed significantly on sandy, silty, and rocky substrates. For sandy substrates, an important factor in the separation of communities was the Novosibirsk Reservoir, for rocky substrates—the influence of the Altai Mountains, and for silty substrates—the location of large cities. The results emphasize the importance of taking into account the differences in bottom sediments and the patterns of longitudinal changes in bottom communities for bio-assessment of the ecological status of large rivers. Overall, we propose macroinvertebrates for bioindication along the Ob River, with regard to type, anthropogenic impact, stress factors, and response of benthic communities.