Nutrient Absorbing Kinetics And Growth Changes Of Phytoplankton Controlled By Different Irradiance, Nitrate And Phosphate Concentration Levels On Autumn In Yangtze River Estuary

Characteristics of phytoplankton population, the nutrient absorption kinetics and growth variation of phytoplankton were studied in this dissertation based on in situ controlled incubation experiment, which were conducted under the coupling between different nutrient concentration and different irradiance in the water region of the Changjiang River estuary. The results showed as follows:1. The uptake rates of phosphate and nitrate by phytoplankton were mainly influenced by light. As the irradiance intensity increasing, the absorption raised obviously. However, in the dark, the nutrient concentration released a little from phytoplankton. The addition of nutrients had an effect on the uptake rates of nitrate and phosphate, but it was unnotable. The absorption enhanced along with the addition of nutrients, then, after when the addition exceeded a certain value, it dropped off. The irradiance has an influence on the amount of nutrient absorption, but the absorption variations of nitrite and ammonia were not remarkable. In low irradiance, the atom ratio of nitrogen and phosphorus absorption was less than Redfiled coefficient 16, whereas this ratio was closed to 16 in high irradiance. In addition, the value of pH was also accelerated along with the increasing of irradiance.2. The growth rates simulated by biomass which represented by Chl a were greater as the irradiance intensity became strong, and in situ irradiance couldn't restrain the growth rates of phytoplankton. The maximum growth rate appeared in between 1 μM and 2 μM of phosphate concentration levels in the phosphorus addition series. At the same time, the better atom ratio of nitrate and phosphate absorption was in between 20 and 30. In the nitrogen addition series, the maximum growth rate appeared in between 20 μM and 25 μM of nitrate concentration and the better ratio was from 30 to 40.3. Synechococcus grew best under the 60% of in situ irradiance, whereas the picoeukaryotes had a high growth rate under 80% of in situ irradiance in phosphorus addition series. In nitrogen addition, the maximum growth rate of Synechococcus was under 80% of in situ irradiance, and that the cell density of picoeukaryotes reached ultimate at 80% of in situ irradiance in the first three days, but the maximum cell density appeared at in situ radiation in the last day. In order to avoid the competition of nutrients, those two phytoplanktons reached their maximum growth rates in different irradiance. Synechococcus made a remarkable response to the addition of...