Comparative Study On The Suitable Growth Conditions And Chlorophyll Fluorescence Characteristics Of Prorocentrum Donghaiense And Skeletonema Costatum

In aquatic ecosystems,phytoplankton have a special niche because they are primary producers.Algal blooms are a phenomenon in which phytoplankton accumulate and multiply and explode in a short period of time.They are also divided into blooms and red tides,which appear in freshwater and seawater,respectively.In recent years,in the eastern coastal areas of China,especially in the coastal waters of Jiangsu and Zhejiang,the main red tide species that have been widespread throughout the year are Prorocentrum donghaiense and Skeletonema costatum.Photosynthesis is the most basic and important physiological characteristic of phytoplankton.Phytoplankton transforms energy in the body through photosynthesis.The photosystem plant's II?PS II?is affected by environmental factors,which causes changes in fluorescence parameters.Two important studies of red tide organisms have certain significance for the further study of the ocean red tide eruption mechanism.In order to understand the effect of the four factors of temperature,light,phosphate,and initial biomass on the suitable growth conditions and chlorophyll fluorescence characteristics of Prorocentrum donghaiense and Skeletonema costatum,temperature,light,phosphate,and initial biomass.The environmental factors are set at four levels,the temperature is 17,20,23,and 26?,the light is 40,80,120,and 160?mol photons/?m² s?,the phosphate is 0.1,1.0,5.0,and 10.0?mol/L,The initial biomass was 1×10⁴,3×10⁴,5×10⁴,7×10⁴ cells/ml.Indoor cultivation experiments were conducted,arranged by L16?4⁵?orthogonal experiment table.The experimental results are as follows.1.It can be seen from the analysis of variance that phosphate has a significant effect on the peak value of chlorophyll a and the peak of cell abundance during the cultivation of Prorocentrum donghaiense and Skeletonema costatum?P<0.01?.2.Prorocentrum donghaiense had a higher chlorophyll a concentration at 17?,23-26?,40-160?mol photons/?m²s?,5.0-10.0?mol/L,3×10⁴-7×10⁴cells/ml.The algae maintains rapid proliferation.In the 16 cultivation experiments,the most suitable growth conditions are 17?,120?mol photons/?m²s?,10.0?mol/L,7×10⁴cells/ml.Under the concentration of 1.0?mol/L phosphate,temperature?26??,light?160?mol photons/?m²s??,initial biomass?7×10⁴cells/ml?are the maximum level combination,the consumption of phosphate can not meet the algal cells growth,chlorophyll a continued to decrease from the 0th day of the culture cycle to 0 on the 8th day,and all algal cells died.The chlorophyll a and the cell abundance of Prorocentrum donghaiense did not decrease to 0,and the addition of phosphates prevented the decline of chlorophyll a and the decline of algal cells,and the changes in cell proliferation lag behind the concentration of chlorophyll a.3.The concentration of chlorophyll a of Skeletonema costatum in the two groups with high phosphate concentration of 5.0?mol/L and 10.0?mol/L in the two groups was rapidly increased at the initial stage of cultivation,and most of the experimental groups reached the peak on the 6th day.In 16 culture experiments,the most suitable growth conditions were 23?,80?mol photons/?m²s?,10.0?mol/L,5×10⁴ cells/ml.Under the conditions of 23?,80-120?mol photons/?m²s?,5.0-10.0?mol/L,5×10⁴-7×10⁴cells/ml,cells proliferate and divide rapidly.At 0.1?mol/L,1.0?mol/L,23-26?,120-160?mol photons/?m²s?light intensity combination,the algal cell metabolism is accelerated and the demand for phosphate is increased.Insufficient phosphate leads to chlorophyll a concentration keep falling.The response of chlorophyll a and cell abundance to Skeletonema costatum under different phosphate concentrations was different.At 0.1?mol/L and 1.0?mol/L,the lower phosphate concentration did not change the chlorophyll a concentration and Algae cells continued to decline,and the group with high phosphate grew fastest.4.Under the phosphate concentration of 5.0?mol/L and 10.0?mol/L in the two groups of Prorocentrum donghaiense and Skeletonema costatum,the fluorescence parameter value is significantly higher than that in the two groups of 0.1?mol/L and 1.0?mol/L.The two groups with high phosphate concentration fluctuated greatly,indicating that the adaptability of the high phosphate environment is stronger.The dinoflagellates of the East China Sea Fv/Fm fluctuated about 0.5 as the baseline,and the growth of algae was severely inhibited when it was lower than 0.3.At this time,the addition of phosphate could not prevent the continuous decline of algae cells,a was less than 0.15 and showed a continuous downward trend The light energy utilization rate of algae is insufficient to maintain algae growth.The photoelectron conversion rate of Prorocentrum donghaiense rETRmax is linearly correlated with the light intensity tolerance IK,and the light has a significant effect on Prorocentrum donghaiense F_v/F_m and a?P<0.05?affecting photosynthetic activity and photosynthesis rate.Skeletonema costatum rETR_max has no linear relationship with I_K,and phosphate has an extremely significant effect on the fluorescence parameters F_v/F_m?P<0.01?.Considering the occurrence of red tide in the actual sea area,combining the analysis of chlorophyll a concentration,algal cell abundance and photosynthesis,Skeletonema costatum has gradually disappeared,and Prorocentrum donghaiense has alternately become the dominant species.At 23?,120?mol photons/?m²s?,1.0?mol/L,1×10⁴cells/ml,red tide succession of Skeletonema costatum and Prorocentrum donghaiense will appear.