Spatial heterogeneity of chemistry of the Small Aral Sea and the Syr Darya River and its impact on plankton communities


Klimaszyk P. Kuczyńska-Kippen N. Szeląg-Wasielewska E. Marszelewski W. Borowiak D. Niedzielski P. Nowiński K. Kurmanbayev R. Baikenzheyeva A. Rzymski P.
November 2022Elsevier Ltd

Chemosphere
2022#307

The shrinking of the Aral Sea represents one of the greatest ecological disasters of modern time. The data on the surviving northern part (Small Aral) is scarce and requires an update. This study aimed to analyze the chemistry, phyto- and zooplankton composition, and their relation in the waters of the Small Aral and its tributary, Syr Darya River. The chemistry of both ecosystems was significantly different. Small Aral was characterized by higher ionic concentrations, salinity, and electric conductivity and more significant spatial variation of chemical properties. The area near the river mouth was more pristine, while the ions concentration and salinity in the distant bays were much higher (>10‰). The highest concentrations of nitrates and total phosphorus in the Syr Darya were observed near Kyzylorda, indicating urban pollution. Overall, 109 phytoplankton taxa were identified in both ecosystems, with diatoms, green algae, and cyanobacteria being most abundantly represented. Oligohalobes dominated, but no polyhalobes and euhalobes algal species were identified. In total, 27 taxa of zooplankton were identified in both studied ecosystems, with the domination of rotifers over microcrustaceans. An exceptionally high level of dominance (65–91%) of rotifer Keratella cochlearis in the Syr Darya was found. The phyto- and zooplankton species richness was higher in the Syr Darya. Plankton communities of the Small Aral reflected horizontal variability of chemical properties. The total phosphorus promoted the prevalence of diatoms, rotifers, and crustaceans. Increased nitrogen concentration promoted cyanobacteria, chlorophytes, cryptophytes and chrysophytes, and rotifers Keratella cochlearis and K. quadrata. The abundance of dinophytes, diatoms Navicula cryptotenella and Cocconeis placentula, green algae Mychonastes jurisii and rotifer Keratella tecta was driven by the higher alkalinity and conductivity/salinity levels. The results represent a reference point for future monitoring of the area and add to understanding the complexity of biological transformations in the Aral Sea and its tributary.

Aquatic chemistry , Aquatic pollution , Aral Sea , Ecosystem recovery , Phytoplankton , Zooplankton

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Department of Water Protection, Adam Mickiewicz University, Poznań, 61-642, Poland
Department of Hydrology and Water Management, Nicolaus Copernicus University, Torun, 87-100, Poland
Department of Limnology, University of Gdańsk, Gdańsk, 80-309, Poland
Department of Analytical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Poznan, Poland
Department of Biology, Geography and Chemistry, Kyzylorda State University, 120000 Kyzylorda, Kazakhstan
Department of Environmental Medicine, Poznan University of Medical Sciences, Poznan, Poland

Department of Water Protection
Department of Hydrology and Water Management
Department of Limnology
Department of Analytical Chemistry
Department of Biology
Department of Environmental Medicine

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