Abstract
Many lakes located in the Songnen Plain of China exhibit a high saline-alkaline level. 25 lakes in the Songnen Plain were selected as research objects in this study. Water samples in these lakes were collected from June to August in 2008. Total Dissolved Solids (TDS) and Total Alkalinity (TA) were measured to assess the saline-alkaline level, and partial canonical correspondence analysis (CCA) was conducted as well. The results show that the majority of these lakes in the study area could be categorized into HCO3−-Na+-I type. According to the TDS assessment, of the total 25 lakes, there are 14 for freshwater, 7 for brackish water and 4 for saltwater; and the respective range of TA was from 0.98 to 40.52. The relationship between TA and TDS indicated significant linear relationship (R2 = 0.9292) in the HCO3−-Na+-I type lakes in the Songnen Plain. There was a general trend that cell density, genera richness and taxonomic diversity decreased with the increase of saline-alkaline gradient, whereas a contrary trend was observed for the proportion of dominant species. When the TDS values were above 3×103mg/L and the TA values were above 15mg/L, there was a significant reduction in cell density, genera richness and biodiversity, and their corresponding values were respectively below 10×106 (ind/L), 15 and approximately 2.5. Through the partial canonical correspondence analysis (CCA), 10.7% of the genera variation was explained by pure saline-alkaline variables. Cyclotella meneghiniana, Melosira ambigua and Melosira granulate were found to become the dominant species in most of these lakes, which indicated that there may be rather wide saline-alkaline niches for common dominant species. About one-quarters of the genera which have certain tolerance to salinity and alkalinity preferred to live in the regions with relatively higher saline-alkaline levels in this study.
Highlights
At present, there are a number of problems of lakes in various parts of the globe, such as lower water level, lesser water area, and higher saline-alkaline level
This paper focuses on the use of environmental data measured from natural water of the lakes in the Songnen Plain, combined with the analysis of partial Canonical Correspondence Analysis to provide a relevant study of phytoplankton
The hydrochemical characteristics in the Songnen Plain are affected by regional climate, hydrogeology, geomorphology and inappropriate human activities
Summary
There are a number of problems of lakes in various parts of the globe, such as lower water level, lesser water area, and higher saline-alkaline level. Saline-alkaline environments of lakes and the resulting change in structure and function of aquatic ecosystem have become the focus of attention [1]. The group of lakes in the Songnen Plain is the chief component of the lakes of Northeast Plain in China [2], and the lakes in the Songnen Plain provide a unique water environment for the study of phytoplankton communities. Its top is covered with Quaternary fluviolacustrine facies sediment with high salt saturation in the rock, and its water solution is alkali. The cations are mainly Na+, and the anions are mainly HCO3- among the salt components [4, 5]. With the essential characteristics of saline and alkaline, these lakes formed in a large-scale regional climate background and hydrological conditions, and surface geochemical actions are special [4]
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