Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, PR China.
Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, PR China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, PR China.
Sci Total Environ. 2024 Jan 10;907:168001. doi: 10.1016/j.scitotenv.2023.168001. Epub 2023 Oct 22.
Metalimnetic oxygen minimum (MOM) is a frequent occurrence in lakes and reservoirs, and its formation is related to the blooming and apoptosis of algae. In this study, the apoptosis mechanism of Chlorella vulgaris (C. vulgaris) and the release of intracellular organic matter (IOM) under different MOM conditions were analyzed by changing the dissolved oxygen (DO) (7.0 mg/L, 3.0 mg/L, and 0.3 mg/L) and water pressure (0.3 MPa and normal pressure). The integrity and auto-fluorescence of algae cells decreased rapidly in the first 8 days, and then stabilized gradually during the development of MOM. Compared with that of water pressures, DO had a significant effect on the activity of algal cells, and higher initial DO levels (3.0 mg/L and 7.0 mg/L) accelerated the lysis of algal cells. The integrity of algae cells decreased to 28.8 %, 31.8 % and 56.6 % at the initial DO of 7 mg/L, 3 mg/L and 0.3 mg/L under 0.3 MPa, respectively. Meanwhile, the concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) continued to increase and reached their maximum at 8 or 12 days, respectively, due to the IOM release caused by algal cell rupture, and then gradually decreased due to microbial degradation. Consistent with the results of membrane integrity, the highest DOC and DON concentrations were found at higher initial DO conditions. By parallel factor analysis, the change in total organic matter fluorescence intensity was consistent with DOC, once again increasing in the first 8 days and then gradually decreasing. The increased humic-like component, which is related to higher aromaticity, led to the monotonic increase of HAAFPs and THMFPs. However, the released IOM of C. vulgaris had lower N-DBPFPs, with TCNMFP predominating primarily. In summary, these results shed new lights on exploring the apoptosis of algae and the release of IOM during the development of MOM.
底栖缺氧（MOM）在湖泊和水库中频繁发生，其形成与藻类的大量繁殖和细胞凋亡有关。本研究通过改变溶解氧（DO）（7.0mg/L、3.0mg/L 和 0.3mg/L）和水压（0.3MPa 和常压）来分析小球藻（C. vulgaris）的凋亡机制和在不同 MOM 条件下细胞内有机物质（IOM）的释放。在 MOM 发展的前 8 天，藻细胞的完整性和自动荧光迅速下降，然后逐渐稳定。与水压相比，DO 对藻细胞的活性有显著影响，较高的初始 DO 水平（3.0mg/L 和 7.0mg/L）加速了藻细胞的溶解。在 0.3MPa 下初始 DO 为 7mg/L、3mg/L 和 0.3mg/L 时，藻细胞的完整性分别降低至 28.8%、31.8%和 56.6%。同时，由于藻细胞破裂导致 IOM 释放，溶解有机碳（DOC）和溶解有机氮（DON）的浓度持续增加，并分别在 8 天和 12 天达到最大值，然后由于微生物降解而逐渐降低。与膜完整性的结果一致，DOC 和 DON 的浓度在初始 DO 较高的条件下达到最高。通过平行因子分析，总有机物质荧光强度的变化与 DOC 一致，在前 8 天增加，然后逐渐减少。增加的腐殖质样成分与较高的芳香度有关，导致 HAAFPs 和 THMFPs 单调增加。然而，小球藻释放的 IOM 具有较低的 N-DBPFPs，TCNMFP 占主导地位。总之，这些结果为探索 MOM 发展过程中藻类的凋亡和 IOM 的释放提供了新的思路。
