Nutritional Niche Of Prorocentrum Donghaiense On N,P,Fe,Mn

Prorocentrum donghaiense Lu belongs to Pyrrophyceae, Prorocentrales, Prorocentraceae, Prorocentrum. The distribution on this species includes the coastal waters of China, Japan, and Korea. In recent years, it has formed massive blooms in the Changjiang Estuary and adjacent waters. In order to understand the rule of four key nutritional factors (nitrogen, phosphorus, iron, and manganese) on the bloom development of P. donghaiense, a series of experiments were carried out to identify the nutritional niche of P. donghaiense on these four nutrient substrates. Concentration gradients were setup for these four nutrients substrates (N, P, Fe, and Mn) that 11 N levels, 11 P levels, 7 Fe levels, and 5 Mn levels, respectively. The cell specific growth rate, maximal cell density, the contents of chlorophyll a, protein, and carbohydrate at critical N concentrations were also measured for P. donghaiense. An orthogonal experiment was also setup to test the effects of irradiance, temperature, and salinity on the growth of P. donghaiense. The results for orthogonal experiment showed the optimal combination of irradiance, temperature, and salinity for P. donghaiense was 88 μmol·m-2·s-1, 21 ℃, and 25. Temperature had the strongest influence on the growth of P. donghaiense. The results from nutritional niche study showed that the lower N optimum concentration limit for the growth of P. donghaiense was 7.962 mg/L, the lower suboptimum concentration limit was 0.115 mg/L. The specific growth rate of P. donghaiense could maintain the optimum level when N concentration was in the range of 10 mg/L to 1000 mg/L. The optimum P concentration ranged from 0.069 to 0.334 mg/L for P. donghaiense, and the suboptimum P range were from 0.022 to 0.069 mg/L, and 0.334 to 17.325 mg/L, unsuitable range were less than 0.022mg/L and more than 17.325mg/L. The optimum range for Fe concentration was from 3.88 to 35.7 μg/L, with the suboptimum range from 0.01 to 3.88 μg/L, and 35.7 to 104 μg/L. The optimum range for Mn concentration was very wide, which ranged from 0.373 to 105 μg/L, with the suboptimum range from 0.001 to 0.373 μg/L. There was a positive relationship between the concentration of chlorophyll a, protein, dissolved carbohydrate and thelevels of N concentrations, and the chlorophyll a concentration per cell in the 10 mg/L treatment was significantly higher than other treatment groups. However, there was no such significant difference in the contents of protein and dissolved carbohydrate per cell among all treatment groups. It further showed that growth rate of P. donghaiense on various N substrates (NH4-N, NO3-N, NO2-N, and urea-N) had no significant difference at eutrophic level (1mg/L) and oligotrophic level (0.1mg/L).