Department of Water Protection, Adam Mickiewicz University, 61-642 Poznań Poland.
Department of Hydrology and Water Management, Nicolaus Copernicus University, 87-100 Torun, Poland.
Chemosphere. 2022 Nov;307(Pt 2):135788. doi: 10.1016/j.chemosphere.2022.135788. Epub 2022 Jul 21.
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.
咸海的萎缩是现代最严重的生态灾难之一。关于现存的北部海域（小咸海）的数据很少，需要更新。本研究旨在分析小咸海及其支流锡尔河的水质、浮游植物和浮游动物组成及其相互关系。这两个生态系统的化学性质有显著差异。小咸海的离子浓度、盐度和电导率较高，化学性质的空间变化也更为显著。河口附近的区域较为原始，而远处海湾的离子浓度和盐度则高得多（>10‰）。在靠近克孜勒奥尔达的锡尔河，硝酸盐和总磷的浓度最高，表明存在城市污染。总的来说，在两个生态系统中都鉴定出了 109 种浮游植物，其中以硅藻、绿藻和蓝藻最为丰富。寡盐生物占主导地位，但没有发现多盐生物和广盐生物藻类。在两个研究的生态系统中总共鉴定出 27 种浮游动物，其中轮虫占优势，而桡足类较少。在锡尔河中，轮虫科的旋轮虫的优势度极高（65-91%）。浮游植物和浮游动物的物种丰富度在锡尔河中更高。小咸海的浮游动物群落反映了化学性质的水平变化。总磷促进了硅藻、轮虫和甲壳类动物的优势地位。氮浓度的增加促进了蓝藻、绿藻、隐藻和金藻以及轮虫旋轮虫和 K. quadrata 的优势地位。双鞭甲藻、硅藻 Cryptotenella navicul 和 Cocconeis placentula、绿藻 Mychonastes jurisii 和轮虫旋轮虫和 K. tecta 的丰度受到较高的碱度和电导率/盐度水平的驱动。这些结果为该地区未来的监测提供了参考点，并增加了对咸海及其支流生物转化复杂性的理解。
