Studies On Cyanobacterial Blooms-Producing Ammonia And The Biologic Effects On Typical Aquatic Organisms

China was one of the countries which had the most serious eruption of cyanobacteria blooms that widely distributed and the most species of cyano-bacteria. The eruption of cyanobacteria blooms not only changed the envi-ronmental factors(low dissolved oxygen, high pH, high chemical oxygen de-mand, et al.), but also produced a large number of derivatives, including mi-crocystin, ammonia, nitrate, hydrogen sulfide and odor substances (sulfoether, 2- methyl isobutyl alcohol camphene, et al.). It seriously affected the water quality and the structure and function of the aquatic ecosystem, and even did harm to the aquatic organisms and human beings. This study focused on cyanobacterial blooms-producing ammonia and the biologic effects on typical aquatic organisms, submersed macrophyte Vallisneria natans L. and fresh-water fish Carassius auratus, and the combined effects of ammonia and Cd on Carassius auratus and the combined effects of ammonia and MC_LR on Cy-prinus carpio L. In an attempt to obtain the data of toxicity and mechanism of eruption of cyanobacteria blooms, the traditional toxicology methods were used, which were combined with molecular biology. This study provided a scientific basis for the system of ecological security threshold on the outbreak of cyanobacterial blooms, and the standards for water safety in different func-tional areas during the process of cyanobacterial blooms diminishing. The major results were summarized as follows:1. Among all those physiological parameters measured, the nitrogen contents in the free amino acids of the plant leaves was the most sensitive indicator. Submersed macrophyte Vallisneria natans L. grew well when the NH4+-N concentration was below 0.60mg/L and stress and growth disturbance happened when it was above 1.00mg/L Results also suggested that defi-ciency of nutrient at a low level of ammonia may cause the induction of free radicals in submerged plant leaves.2. Among all those physiological parameters measured, the activity of SOD and CAT and the contents of MDA in the liver proved to be the most sensitive indicators.NH4+-N induced oxidative stress of the liver in Carassius auratus at concentration of 0.50mg/L(NH3-N 0.008mg/L), and induced oxida-tive damage and protein damage at concentration of 5.00mg/L(NH3-N 0.086 mg/L).3. Among all those physiological parameters measured, the activity of SOD in the liver proved to be the most sensitive indicator to Cd exposure. Oxidative stress of the liver in Carassius auratus was induced at concentration of 0.005 mg/L Cd and 0.50mg/L NH4+-N(NH3-N 0.006mg/L). Oxidative damage of the liver in Carassius auratus was induced at concentration of 0.005 mg/L Cd and 1.00mg/L NH4+-N(NH3-N 0.013mg/L).4. Oxidative stress of the liver in Cyprinus carpio L. was induced at concentration of 1.0μg/L MC_LR,10.0mg/L NH4+-N(NH3-N 0.006mg/L)and combined effect of MC_LR and NH4+-N. The results did not show that the combined effects of MC_LR and ammonia more toxic than a single one.In summary, NH4+-N would have an effect upon aquatic plants and fish when its concentration were in excess of 0.50mg/L The combined effects of Cd and ammonia were more toxic than the single effects of Cd. The combined effects of MC_LR and ammonia were not more toxic than a single one.