Large-Scale Hydromorphological Characteristics Of The Proglacial River Katun (Ob Headwaters)

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.

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

Yanygina,

Schletterer

2023

Zooplankton as an indicator of hydrological connectivity of the main channel and the floodplain in a large river system

Yanygina,

Burmistrova,

Kotovshchikov

et al. 2023

The connectivity of the river–floodplain system during floods plays a decisive role in organisms/matter contribution to the ecosystems of large lowland rivers. We hypothesized that the direction of water-level trends during flood was crucial for zooplankton release from the floodplain into the river channel. The seven-year study of zooplankton in the large plain Ob river suggest that at the inundated floodplain even a slight water level fall brings to plankton release from the floodplain into the river thus causing its abundance boom in the main channel. At water-level stabilization or rise, zooplankton communities of floodplain become isolated from the channel that ceases the recruits’ inflow from the floodplain and brings to a sharp drop in number of river zooplankton. Therefore, it is necessary to take into account dynamics trends (i.e., fall or rise) in river water level when assessing zooplankton density in large lowland rivers. The analysis of such trends should become the basis for predicting of river zooplankton abundance and assessing changes in feeding conditions of fish during the growing season.

Why do phyto- and zooplankton exhibit different patterns of seasonal dynamics in the large Ob river-floodplain system (West Siberia)?

Yanygina,

Burmistrova,

Kotovshchikov

et al. 2024

A floodplain is considered as the basis for high production and biodiversity of large rivers. To test the hypothesis of the determining role of the floodplain as a supplier of plankton to the channel of a large unregulated river, we implemented a three-year study in the Ob river-floodplain (West Siberia, Russia) and revealed that factors of seasonal dynamics and sources of phyto- and zooplankton supply to the channel differed. The riverine phytoplankton was formed mostly in the main river and small side channels. The driving factor of its seasonal dynamics in the main channel and the permanently connected floodplain was water temperature, whereas in mostly isolated floodplain lakes—it was the availability of nutrients. Zooplankton in the channel was largely formed due to “recruits” arrival from the floodplain reaches. Its abundance in the channel with connection to the river-floodplain areas depended on temperature and phytoplankton amount. This study casts a light upon some major factors of seasonal dynamics of phyto- and zooplankton in the river-floodplain systems of large lowland rivers and serves the basis for the development of the flood pulse concept and monitoring program for rivers with a long freeze-up period.