Abstract

The change in phytoplankton along the length of the Ural River from Verkhneuralsk to Orenburg (on a site of more than 1000 km) has been studied for the first time. The powerful eutrophying effect of Magnitogorsk on the river for more than 150 km has been revealed. It manifests itself in the fact that the phytoplankton biomass in this area increases greatly, averaging about 15 mg/L (with the dominance of cyanobacteria Microcystis aeruginosa), whereas the species diversity index (Shannon index), on the contrary, reaches extremely low values of 0.25. This indicates a significant oppression of the plankton community and deterioration of water quality. In the Ural River above this site (from Verkhneuralsk to Magnitogorsk reservoir), as well as below it (from Orsk to Orenburg), phytoplankton indicators correspond to the usual values of 1.6–1.7 mg/L of biomass, with a Shannon index of 3.3–3.5 (on average for each site). This suggests that the conditions for the existence of plankton in the upper and lower areas are favorable. At the same time, the sites differ in the composition of algae: the first is dominated by diatoms and the second is mainly dominated by green algae. This may be due to geographical factors: in the north, the Ural River flows in the forest-steppe zone, and in the south it flows in the steppe.

中文翻译：

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富营养化条件下乌拉尔河沿岸浮游植物的变化

摘要

首次研究了乌拉尔河从上纽拉尔斯克到奥伦堡（1000多公里长）沿线浮游植物的变化。马格尼托哥尔斯克对150多公里河流的强大富营养化效应已经显现。表现为该区浮游植物生物量大幅增加，平均约15 mg/L（以蓝藻铜绿微囊藻为主），而物种多样性指数（香农指数）却达到极低值0.25。这表明浮游生物群落受到严重抑制和水质恶化。在该地点上方（从上纽拉尔斯克到马格尼托哥尔斯克水库）及其下方（从奥尔斯克到奥伦堡）的乌拉尔河中，浮游植物指标对应的生物量通常值为 1.6–1.7 毫克/升，香农指数为 3.3 –3.5（每个站点的平均值）。这表明上部和下部区域浮游生物的生存条件是有利的。同时，这些地点的藻类组成也有所不同：第一个以硅藻为主，第二个主要以绿藻为主。这可能与地理因素有关：乌拉尔河在北部流经森林草原地带，在南部流经草原。