Ammonium, microcystins, and hypoxia of blooms in eutrophic water cause oxidative stress and C–N imbalance in submersed and floating-leaved aquatic plants in Lake Taihu, China

• Published in: Chemosphere (Oxford) Vol. 82; no. 3; pp. 329 - 339
• Main Authors: Zhang, Meng, Wang, Zhengqi, Xu, Jun, Liu, Yaqin, Ni, Leyi, Cao, Te, Xie, Ping
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: ammonium compounds; Animal, plant and microbial ecology; Antioxidant activity; Applied ecology; Aquatic macrophytes; Aquatic Organisms - drug effects; Aquatic Organisms - growth & development; Aquatic Organisms - metabolism; Aquatic plants; Biological and medical sciences; Blooms; carbon; Carbon - analysis; Carbon - metabolism; Carbon Cycle; China; Cyanobacteria; Cyanobacteria - growth & development; C–N balance; Ecotoxicology, biological effects of pollution; Environmental Monitoring; enzyme activity; Eutrophic waters; Eutrophication; formula omitted; free amino acids; Fresh Water - chemistry; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; Hypoxia; Lakes; Microcystins; Microcystins - analysis; Microcystins - toxicity; Nitrogen - analysis; Nitrogen - metabolism; Nitrogen Cycle; Oxidative Stress; oxygen; Plant Development; plant stress; Plants (organisms); Plants - drug effects; Plants - metabolism; protein content; Quaternary Ammonium Compounds - analysis; Quaternary Ammonium Compounds - toxicity; secondary metabolites; stress tolerance; Stresses; submerged aquatic plants; superoxide dismutase; Toxic; toxicity; Water Pollutants - analysis; Water Pollutants - toxicity; China; Asia; Hypoxia; NH 4; C–N balance; Antioxidant activity; Aquatic macrophytes; Microcystins; Oxidative stress; Ammonium; C-N balance; Nitrogen; Carbon; Water stress; Eutrophication; Freshwater environment; Bloom; Lakes; Water pollution; NH; Aquatic plant; Balance
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2010.10.038

The heavy bloom of cyanobacteria is a disastrous consequence of freshwater eutrophication, and the bloom is highly toxic due to its secondary metabolites called microcystins (MCs). The release of organic substances from dense blooms causes an increase in NH 4 + and decrease in oxygen in lake water. In the present study, the dynamics of physio-biochemical responses of five aquatic macrophytes to MCs and NH 4 + stresses in Meiliang Bay were evaluated. The bay is one of the most seriously eutrophized areas dominated by the toxic cyanobacteria of Lake Taihu, China. The results demonstrate that aquatic macrophytes in Meiliang Bay are subjected to successive external stresses. From January to May, they are subjected to high NH 4 + stress (>0.56 mg L −1), whereas from June to September or during dense blooms, the macrophytes experience both MC proliferation and moderate NH 4 + toxicity (>0.3 mg L −1). In August, high NH 4 + stress occurs along with hypoxia stress, whereas from September to December, the macrophytes experience moderate NH 4 + stress, causing a serious imbalance in C–N metabolism and oxidative stress. Between the two aquatic plant life forms, floating-leaved plants are more resistant to the stresses of eutrophication than are submersed plants. Elevated MCs in the water column can aggravate oxidative stress and suppress the soluble protein contents of aquatic plants. High NH 4 + in the water causes severe C and N imbalance in submersed macrophytes because of considerable carbon consumption for free amino acid synthesis. The superoxide dismutase activities of submersed macrophytes are suppressed by low light penetrating the eutrophic water, which might impair the antioxidative function of the plants. The findings of this study provide mainly field evidence that reveals the physical, chemical, and biological stresses on aquatic plants in bloom-prevailed eutrophic lakes.