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

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.

Choice of benthic macroinvertebrate‐based metrics for assessing water quality in the littoral zone under anthropogenic disturbance in southern Lake Kivu (East Africa)

“…Physico‐chemical parameters are the first environmental variables to be impacted by disturbances that may occur in the water body and its watershed (Calmuc et al, 2020; Pandey et al, 2018; Saal et al, 2020). Also, the physico‐chemical parameters of waters are considered as the most important factors to be able to influence the species composition, diversity, stability, production and physiological conditions of biological community assemblage in a water bodies (Barinova & Mamanazarova, 2021; Pissaridou et al, 2021). In this study, the results showed that four (DO, Turbidity and the nutrients PO 4 3− and NO 2 − ) of the 11 measured parameters (Table 3) recorded values above the recommended limits for the sustainability of life in the aquatic environment (ANZECC, 2000; CCME, 1999; USEPA, 1986, 1995).…”

“…Comparisons of the sensitivity of these nine metrics resulted in only six (number of EPT taxa, % Dipt, % Chironomidae, % Ephemeroptera or % EPT and FBI) being selected as the metrics that could properly discriminate between reference and disturbed sites as also observed elsewhere (e.g., Camargo, 2019; Gabriels et al, 2010). EPT and Dipteran groups including chironomids showed predictable responses to low oxygen levels and over‐enrichment of key nutrients in the water, which explains their use in many studies to assess nutrient enrichment (e.g., Barinova & Mamanazarova, 2021; Serra et al, 2016). In this study, there was correlation between these groups and oxygen, a parameter that did not record very low values (>6 mg/L in four stations and 5.3 to 5.8 mgl/L in four other stations).…”

“…EPT and Dipteran groups including chironomids showed predictable responses to low oxygen levels and over-enrichment of key nutrients in the water, which explains their use in many studies to assess nutrient enrichment (e.g., Barinova & Mamanazarova, 2021;Serra et al, 2016). In this study, there was correlation between these groups and oxygen, a parameter that did not record very low values (>6 mg/L in four stations and 5.3 to 5.8 mgl/L in four other stations).…”

“…Human activities (rapid urbanization, dams, and irrigation) alter aquatic ecosystems, ecological integrity, and water quality (Ntislidou et al, 2018; Tsanis et al, 2006). As this phenomenon has become a major concern for many states, several approaches, including physico‐chemical (Calmuc et al, 2020; Pandey et al, 2018; Saal et al, 2020) and biological (Baptista et al, 2007; Barinova & Mamanazarova, 2021; Pissaridou et al, 2021; Pont et al, 2021) approaches, have been developed to monitor and to assess the impacts of pressures from anthropogenic and natural stressors on surface and groundwater qualities (Pont et al, 2021; Saal et al, 2020).…”

Isolation basin stratigraphy and Holocene relative sea-level change on the Barents Sea coast at Teriberka, Kola Peninsula, northwestern Russia

“…Diatom analysis was based on standard methods (Barinova et al, 2006; Gleser et al, 1992; Proshkina-Lavrenko et al, 1974). Diatoms in one sediment core from Lake 4 were studied by express method, that is, without preparation of permanent slides.…”