State Key Laboratory of Pollution Control and Research Reuse, School of the Environment, Nanjing University, Nanjing, China.
Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL, United States of America.
PLoS One. 2020 Dec 22;15(12):e0243582. doi: 10.1371/journal.pone.0243582. eCollection 2020.
Bloom-forming cyanobacteria dramatically influence nutrient cycling in eutrophic freshwater lakes. The phosphorus (P) assimilation and release of bloom-forming cyanobacteria significantly may also affect the phosphorus source and amounts in water. To understand the phosphorus release process of bloom-forming cyanobacteria below the accumulated surface and sedimentary bloom-forming cyanobacteria, the degradation of bloom-forming cyanobacteria dominated by Microcystis spp. at different cell density in the dark was investigated over a 25-day microcosm experiment. The dissolved inorganic phosphorus (DIP) and dissolved total phosphorus (DTP) contents increased with the increment of cyanobacterial density, and the dark status markedly increased the proportion of DIP in water during the decline period of bloom-forming cyanobacteria. Meanwhile, the process of cyanobacterial apoptosis accompanied by the changes of malondialdehyde (MDA) and phosphatase (AKP) contents, and the increases of superoxide dismutase (SOD) and catalase (CAT) activities of cyanobacteria in the dark, especially in low-density groups (5.23×108 cells L-1), which further affect the physicochemical water parameters. Moreover, the DIP release from high-density cyanobacteria (7.86×107 cells L-1~5.23×108 cells L-1) resulted from the relative abundance of organophosphorus degrading bacteria in the dark. Therefore, the fast decay of cyanobacteria in the dark could accelerate DIP release, the high DIP release amount from accumulated bloom-cyanobacteria provide adequate P quickly for the sustained growth of cyanobacteria.
形成水华的蓝藻显著影响富营养化淡水湖中营养物质的循环。形成水华的蓝藻对磷的吸收和释放也可能影响水中磷的来源和含量。为了了解水下积累层和沉积物中形成水华的蓝藻的磷释放过程，在为期 25 天的微宇宙实验中，研究了不同细胞密度下以微囊藻为主的形成水华的蓝藻在黑暗中的降解情况。随着蓝藻密度的增加，溶解性无机磷（DIP）和溶解性总磷（DTP）含量增加，在形成水华的蓝藻衰退期间，黑暗状态显著增加了水中 DIP 的比例。同时，伴随着丙二醛（MDA）和磷酸酶（AKP）含量的变化，以及蓝藻中超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性的增加，蓝藻的凋亡过程，尤其是在低密度组（5.23×108 个细胞 L-1）中，这进一步影响了理化水参数。此外，高密度蓝藻（7.86×107 个细胞 L-1~5.23×108 个细胞 L-1）在黑暗中由于有机磷降解菌的相对丰度而导致 DIP 的释放。因此，黑暗中蓝藻的快速衰减可以加速 DIP 的释放，积累的水华蓝藻中大量的 DIP 释放为蓝藻的持续生长提供了充足的磷。
