Diatom Algae-Indicators of Water Quality in the Lower Zarafshan River, Uzbekistan

Sophia Barinova,Karomat Mamanazarova

doi:10.3390/w13030358

Abstract

This work is the first, the purpose of which was a comprehensive assessment of the ecological state of the lower reaches of the Zarafshan River using bioindication of water quality by diatoms based on species’ ecological preferences, pollution indices, statistics, and ecological mapping. A total of 198 species and subspecies of diatoms were first identified from 195 samples collected four times a year at six sites in the lower reaches of the Zarafshan River in 2009–2015. The richest species were Cymbella, Navicula, and Nitzschia. Pleurosira laevis, resistant to salinity, was first found in aquatic habitats in Uzbekistan. Bioindicators of nine environmental variables make up 91% of the list. Distribution analysis of variables, pollution indices (SLA—SládečDek index of saprobity), and toxicity indices (WESI—Water Ecosystem State Index) show increases in salinity, turbidity, and decreases in organic pollution downstream. The source of acidification can be the Navoi region. We found an increase in the ability to self-purify with an increase in species richness and abundance of diatoms in the lower part of Zarafshan. Thus, the ecosystem of the studied part of the river successfully copes with the incoming pollution from the middle part of Zarafshan and demonstrates some stability and successful self-purification with a water quality class of 2–3. The first studied lower reaches of the ecosystem of the Zarafshan River using bioindicators, statistics, and ecological mapping show that the problem of aridization in Central Asia does not necessarily lead to degradation of the river ecosystem and an increase in pollution, but with rational water use can improve water quality and self-purification processes. Hence, diatoms can be good indicators of river water quality in a semi-arid region and reflect the climate and anthropogenic load change. We recommend that attention be paid to nutrient and turbidity management and to expand state monitoring points to the lower part of the river up to the Karakul region.

Highlights

Algae, being mostly autotrophic, form the basis of the trophic pyramid and, are the first to participate in the production of organic matter in the aquatic ecosystem, using biogenic compounds of nitrogen and phosphorus, as well as dissolved organic matter and play an important role in self-purification of water [1]
According to the chemical data (Table 2), the content of heavy metals and heavy orAccording to the chemical data (Table 2), the content of heavy metals and heavy organic pollutants from the sources of industrial and agricultural pollution on the catchment ganic pollutants from the sources of industrial and agricultural pollution on the catchment basin were at a low level in the studied part of the lower Zarafshan River
Bioindication of other variables dynamic that we revealed with bioindication methods has never been studied in the Zarafshan river course

Summary

Introduction

Algae, being mostly autotrophic, form the basis of the trophic pyramid and, are the first to participate in the production of organic matter in the aquatic ecosystem, using biogenic compounds of nitrogen and phosphorus, as well as dissolved organic matter and play an important role in self-purification of water [1]. The intensity of the biogenic load on water bodies is reflected by the abundance of algae developing under these conditions and their species composition [2,3]. The algal community’s characteristics, such as the abundance, biomass, and species composition, are used in bioindication methods to detect water quality changes [1]. The most developed system of bioindicators is based on diatoms [4]. These methods provide a comprehensive assessment of the results of all processes occurring in a water body. Bioindication using algal communities is a cheap express method, and chemical analysis requires certain financial costs, instrumental base, and relevant legislation [5]

Methods

Results

Discussion

Conclusion