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| Effects of nitrogen/phosphorus ratios on algae growth in the Beiluo River |
| Received:December 01, 2022 Revised:February 16, 2023 |
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| KeyWord:Beiluo River;nitrogen/phosphorus ratio;eutrophication;algae |
| Author Name | Affiliation | E-mail | | YANG Zhen | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | ZHANG Huiqiang | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | CHEN Jing | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | ZHAO Rongna | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | ZHANG Chun | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | ZHANG Qinming | Shaanxi Environmental Monitoring Center, Xi'an 710054, China | | | YIN Xianqiang | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | FAN Xiaoteng | College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China | fanxiaoteng@nwafu.edu.cn |
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| Abstract: |
| This study collected water samples from the Xiatao Hydropower Station dam, Beiluo River, and added phosphate to elevate the total phosphorus concentration and modify the nitrogen/phosphorus ratios to explore the algae growth and diversity in Beiluo River under different nitrogen/phosphorus ratios. In total, 11 groups with varying total phosphorus concentrations(0.02, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50 mg·L-1)were set up for 5-day cultures. Results showed that the identified algae belonged to 31 genera and 4 phyla in the culture conditions, among which Microcystis, Merismopedia of the phylum Cyanobacteria, and Scenedesmus, Crucigenia, and Placoma of the phylum Chlorophyta were the dominant species that accounted for a relatively high proportion of algae in the Beiluo River. The algal abundance gradually increased with the total phosphorus concentrations, and the highest was in the 0.40 mg·L-1 group. The dominant algae grew rapidly when the total phosphorus concentration was higher than 0.10 mg·L-1, resulting in a significant increase in the species richness index(P<0.05)and significant decreases in the Shannon diversity index, Simpson dominance index, and Pielou evenness index(P<0.05). Besides, the determination of nitrogen and phosphorus in water samples showed that the absorption of total nitrogen by algae was accelerated with the increased input of exogenous phosphorus concentrations. The total nitrogen uptake was accelerated, and the nitrogen/phosphorus uptake ratios tended to plateau when the total phosphorus concentration exceeded 0.10 mg·L-1. In summary, the present study found that the input of phosphorus could promote the absorption rate of total nitrogen by algae, increasing the risks of rapid growth and algal blooms of the Cyanobacteria and Chlorophyta phyla when the concentration of total phosphorus ≥ 0.10 mg·L-1. |
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