| The response mechanisms of nitrate reductase activity, alkaline phosphatase activity, protein, carbohydrate and other major biochemical characteristics of dominant bloom-forming species (Prorocentrum donghaiense) on different nutrients were studied. The effects of nitrate and phosphate on the major biochemical characteristics of Prorocentrum donghaiense were determined, and the distribution of nutrient concentration and alkaline phosphatase activities in the Yangtze estuary sea were studied in order to provide some biological indicators for further accurate evaluation of the eutrophication. The main research contents are as follows:The relationship between growth, main biochemical indicators of Prorocentrum donghaiense and nitrogen, phosphorus in the outside environment were studied through batch culture in the laboratory, the results showed that:①Nitrogen, phosphorus nutrition elements were necessary elements of Prorocentrum donghaiense during its growth and reproduction. Prorocentrum donghaiense couldn't normally grow in the environment without nitrogen or phosphor.②The nitrate and phosphate concentration could affect the nitrate reductases activity. In the two treatment groups without nitrate or phosphate, NRA kept a lower level; cellular began to decline in the second growth day. In different conditions of nitrate and phosphate concentration, NRA increased in the beginning days and arrived at maximum in the period of exponential growth, then decreased with the extending of the culture time. The maximum cellular density of Prorocentrum donghaiense had a lagging effect which was not consistent with the NRA maximum. NRA increased with the initial nitrate and phosphate concentration increasing. There existed the positive relation between growth rate, nitrate incorporation rate andNRA, which could predict Prorocentrum donghaiense's absorption of nitrate. The nitrogen and phosphorus of Prorocentrum donghaiense in the environment could affect the maximum nitrate reductases activity, thus influenced the absorption of nitrate. The results showed when N/P was 16, the maximum nitrate reductases activity of Prorocentrum donghaiense was highest, and the utilization efficiency of nitrate reached the maximum.③Alkaline phosphatase activities, protein and carbohydrate content of Prorocentrum donghaiense were influenced by nitrogen and phosphorus. In the batch culture, alkaline phosphatase and carbohydrates showed ascendant trend with the extending of the time, while protein content reduced without nitrate or phosphate. In other groups with different nitrogen and phosphorus concentration, nitrogen and phosphorus in the environment were plenty; the cells splited rapidly; alkaline phosphatase, carbohydrates declined while protein content rised as nutrient consumed at the beginning of the experiment, In the latter experiments, nitrogen and phosphorus nutrient were exhausted, cell division was slow and maintained relative stability. Alkaline phosphatase and carbohydrates rised while protein content declined as nutrient consumed, therefore, low concentration phosphate could help to increase the activity of alkaline phosphatase. Throughout the trial process, the change of protein content was small probably in that protein was the main structural components. The content of carbohydrates, an important materia for energy storage, increased when the nutrient run out, which has important significance for cells adapting to low nutrition environment and providing energy. The relevant analysis of three biochemical components with nitrogen and phosphorus was studied. The correlation of carbohydrate content and alkaline phosphatase activities was very well, and could reflected phosphate status of cells. Therefore carbohydrate content and alkaline phosphatase activity could be used as instructions parameters of phosphate limitation.The investigation of nutrient concentration and alkaline phosphatase activities in Changjiang Estuary and adjacent area was made in May, 2010. The results showed that, the concentration of surface TN, TP, NO3-N, PO4-P and SiO3-Si had Similar trends that the nutrient concentration inshore were much higher than that offshore; the isolines of TN and TP nearly paralleled with the coastline; the distribution shape of SiO3-Si, NO3-N and PO4-P concentration were similar to tongue; the isolines of NH4-N concentration and salinity inshore were much lower than those offshore. The distribution of surface alkaline phosphatase activity and nutrient concentration were opposite, which inshore was much lower than that offshore. The low value zone of alkaline phosphatase activity was similar to"mushroom". With the effect of Yangtze estuary water, the difference between salinity on surface and that in bottom is large, and the surface concentration of TN, NO3-N and PO4-P was higher than that in bottom while alkaline phosphatase activity was opposite in the sea area to the west of 122.5°E. With the effect of the coean, the changes of alkaline phosphatase activity and nutrient were complex in the sea area to the east of 122.5°E. APA and some eutrophication indexes existed good correlation, which was better to reflect the extent of eutrophication... |
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