The Dredging Impact on the Lake Manzherok (Republic of Altay) Hydro/biological and Sanitary/micro/biological Characteristics

The article assesses ecological status of the Lake Manzherok (Republic of Altay Mayminsk Rayon) by its hydro/biological and sanitary/micro/biological characteristics after completion of dredging works. To estimate the bio/ceonosis dynamics we used the archive data of 2007–2015 and references. The aquatic communities demonstrated low indicators of development, phytoplankton – 26 taxons, abundance did not exceed 1.3·103 thousand cells/m3, biomass did not exceed 64.0·10-3 mg/m3. In water we found the sapropel vegetative pigments with the chlorophyll a of 237 mg/m3. We identified 16 species of zooplankton with 3. 5 –18.2 t housa nd pieces/m3 abu nda nce w it h 23.4 –97. 3 mg/m3 biomass. In comparison with 2015 the filtering zooplankton organisms’ abundance and biomass were 10–15 times lower. In contrast with 14–15 species in previous years we identified 5 species of macrophytes. The benthos abundance was not more than 1.48 thousand pieces/m2, the biomass did not exceed 1.56 g/m2, that is lower than in 2007. Such low indicators of the aquatic communities’ development with high concentration of organic matter argue the temporal state of anthropogenic metabolic regress. The Lake Manzherok water quality by its sanitary/micro/biological characteristics did not agree with the requirements to recreational water bodies. The whole content of coliform bacteria in the off-shore zone 25 times exceeded the norm, while the content of thermo/tolerant coliform bacteria in the center of the lake and in the macrophytes tangle 2.3 times exceeded the norm.

TO THE PROBLEM OF TOTAL EVALUATING OF DREDGING IMPACT ON VARIOUS SYSTEMATIC GROUPS OF AQUATIC BIOLOGICAL RESOURCES OF THE NOVOTROITSK RESERVOIR IN THE STAVROPOL REGION

The article highlights the poor ecological conditions of the Novotroitsk reservoir in the Stavropol Territory due to its intensive siltation because of the erosion of the banks and riverbed of the Egolik river, forming extensive stagnant zones and waterlogging of individual sections and secondary organic pollution of the reservoir, which necessitated a set of measures for hydromechanical cleaning of the reservoir bottom from silt sediments. There have been given the results of comprehensive studies of the possible impact of dredging by hydro-mechanization using pile-anchor dredger “350-50L” on the aquatic biological resources of the Novotroitsk reservoir. The hydrological, hydrobiological and ichthyological characteristics of the biota of the Novotroitsk reservoir are given, the technological solutions used in the course of dredging are fully described, the influence of the dredging on various systematic groups of hydrobionts of the reservoir is considered. According to the current regulatory legal acts of the Russian Federation in the fisheries and saving aquatic biological resources, there has been carried out calculation of harm caused to the aquatic biological resources. In view of the research results, the main features of the negative impact have been identified and the total amount of harm caused to the aquatic biological resources of the Novotroitsk has been calculated reservoir in natural terms. Using a certified computer model of IMRV “Potok” 1.0 there has been conducted simulation mathematical modeling of propagation and sedimentation of additional turbidity. The values of change variability of the suspended solids concentrations depending on the distance, the integral volumes of suspension tails and redeposition areas of turbidity zones on the bottom of the Novotroitsk reservoir relative to the month of conducting the work and to the seizures of the extracted soil have been calculated. Various compensatory measures for restoration of water bioresource losses have been developed.