Nature Conservation Research: Заповедная наука (May 2020)
Zoobenthos in watercourses and water bodies in the Bolonsky State Nature Reserve (Russia)
Abstract
Invertebrates play a major role in food chains, being the main feed stock for many vertebrates. So far, the benthic fauna communities are still poorly studied in many water body types, including wetlands in the River Amur basin. In 2015–2018, we conducted for the first time the study of zoobenthos in water bodies located in the Bolonsky State Nature Reserve (Khabarovsky Krai, Russia). We present data on the general taxonomic composition and occurrence of benthic invertebrates in rivers and lakes. In addition, information on the structure, density and biomass of their populations is provided. The environmental assessment of the water bodies of the Protected Area has been performed on the basis of zoobenthos composition. Quantitative samples of benthos were collected using the GR-91 rod bottom scoop from a depth from 50 cm to 400 cm and using the folding benthometer until a 25-cm depth. All sampled were fixed in a 4% formalin solution. Amphibiotic insect adults were collected using an entomological net and light traps. These samples were fixed in a 75–96% ethanol solution and processed according to the generally accepted methods. A total of 168 taxa from 15 systematic hydrobiont groups were recorded. The majority of them were Chironomidae (87 species), Trichoptera (18 species) and Ephemeroptera (16 species). Quantitative indicators of organisms were correlated with the seasonal fluctuations in the hydrological regime and the soil type. During floods, the quantitative sampling of zoobenthos was impossible. During a low-water period, studies were available predominantly in small and medium rivers and channels in which entry by boat is possible. In lakes, we found low quantitative values of density and biomass of benthos (297 ± 91 individuals/m2 and 0.1 ± 0.1 g/m2). The average values of density and biomass were respectively 824 ± 267 individuals/m2 and 8.6 ± 8.1 g/m2 in streams, 1298 ± 538 individuals/m2 and 11.2 ± 5.8 g/m2 in small rivers, and 473 ± 76 individuals/m2, and 23.3 ± 9.7 g/m2 in medium rivers. Clean sand was the poorest soil in lakes and rivers. In areas with a slowed flow in springs and channels, the presence of silty-sandy soils with an admixture of detritus provides a higher number of habitats suitable for the aquatic organisms in contrast to the main riverbeds of lowlands. We demonstrated that in water bodies, the conditions favourable for the benthic communities are observed on plant root systems immersed in water along riverbeds, in channels and bays, and on silty sands with a rich admixture of detritus at an average depth of 1.7 m. The density and biomass of zoobenthos varied from 6 individuals/m2 to 25 110 individuals/m2 and from < 0.1 g/m2 to 11 81.9 g/m2. The average density of benthic populations was 692 ± 119 individuals/m2 and the average biomass – 16.9 ± 5.8 g/m2. High values of benthos density were recorded in the summer period, while high values of the benthos biomass was observed in the spring period. During the vegetative seasons, Chironomidae, Oligochaeta, Mollusca, and Trichoptera dominated in the zoobenthos composition. This is related with their life cycles and the influence of various abiotic factors (floods, current velocity, water temperature, oxygen regime, soil nature). We found that the proportion of Mollusca was 89% of the total zoobenthos biomass, while proportions of Oligochaeta and Chironomidae were respectively 60% and 26% of the total density. Higher values of the occurrence frequency were demonstrated for Chironomidae (100%) and Oligochaeta (95%). Hydra, Planaria, aquatic mites, Asellidae, Odonata, black flies, Ephydridae, and Coleoptera were rarely recorded (< 10%). Permanent components of the benthic communities were eurybionts and limnobionts belonging to Chironomidae, Oligochaeta and Nematoda, which inhabit preferably channels and sites with a slowed current velocity, namely lakes and mires. The absence of oxyphilic species of Plecoptera, Deuterophlebiidae, and Blephariceridae was characteristic. This is comparable with wetlands around the world. The most interesting records were Amuranodonta boloniensis and Cristaria herculea included in the various-rank Red Data Books, as well as Monodiamesa kamora known only in the Lower Amur River basin. Two Chironomidae species, Heterotrissocladius simmiensis, Propsilocerus amurensis, have been described for science for the first time on the basis of samples collected in the Bolonsky State Nature Reserve. Finally, Axarus fundorum is a new species in the Russian fauna. According to biological indication data, the water bodies of the Bolonsky State Nature Reserve belong to a clean type. They are characterised by high environmental status and meet the requirements of the European Framework Water Directive (WFD), which is required to create a network of reference targets. The presence of new and threatened species indicates the uniqueness of the wetlands in the Lake Bolon neighbourhood and the need for their conservation and further investigations.
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