Research And Application Of Optimal Design Of Fluorescence Kinetic Measurement Technology For Phytoplankton Primary Productivity

The primary productivity of phytoplankton is the ability of phytoplankton to absorb CO2 to synthesize organic matter through photosynthesis,and it is the basis of material and energy in aquatic ecosystems.The measurement of the primary productivity of phytoplankton mostly adopts,culture,and laboratory analysis modes.The measurement cycle is long and the cost is high.The rapid and accurate measurement of the primary productivity of phytoplankton is important for the evaluation of aquatic ecosystem carrying capacity,aquatic ecosystem quality evaluation,and research on ocean climate change.The scientific significance and application value.The chlorophyll fluorescence kinetics method can realize the rapid measurement of the primary productivity of phytoplankton,but the instrument status,environmental conditions and model parameter settings will affect the accuracy of the measurement results.In this paper,different phylum algae species are used as the measurement objects,the method for accurate measurement and correction of phytoplankton primary productivity based on fluorescence kinetics is studied,the auxiliary function module of the rapid in-situ monitor for phytoplankton primary productivity is designed,and the field measurement application verification is carried out.The main research results obtained are as follows:(1)The accurate measurement method of algae photosynthetic fluorescence parameters by fluorescence kinetics method was studied.The effect of instrument noise on the measurement of photosynthetic fluorescence parameters was studied.The results showed that the corrected Fv/Fm value was about 0.60,the relative error was 1.2%,and the accuracy was improved by 23%.The adaptive control method of excitation light intensity was studied,and the photo synthetic fluorescence parameters were screened.E?,to achieve rapid and accurate excitation light emphasis control for different species of algae.The results show that under different initial conditions of light intensity,stable excitation light intensity can be obtained after adaptive adjustment and the light intensity RSD is less than 2.5%,Fv/Fm measurement value The results are consistent with those of Fast-Ocean;the influence of water turbidity on the measurement accuracy of photo synthetic fluorescence parameters and the correction method are studied.After correction,the relative standard deviations of Fo and Fm are 0.52%and 0.69%,respectively.(2)The correction method of photosynthetic size unit in the measurement of phytoplankton primary productivity is studied.Based on the excitation spectroscopy,the accurate acquisition of the proportions of the components of the mixed algae was achieved.Based on this,the photo synthetic size unit of the mixed algae was calculated and the primary productivity of the mixed algae was corrected.The experimental comparison and verification with the photosynthetic oxygen evolution method was completed.The results showed that the measurement error of primary productivity of pure cyanobacteria,green algae and dinoflagellate decreased from 38.8%,14.3%and 13.2%before correction to 3.9%,4.1%and 5.2%;the maximum and average measurement errors of primary productivity of mixed samples were corrected by correction.The former 20.4%and 15.2%dropped to 4.5%and 5.2%.This method solves the problem of the measurement deviation of the primary productivity of algae in the aquatic ecosystem caused by the fixed value of the photosynthetic size unit.(3)The correction method of algae light absorption coefficient in the measurement of phytoplankton primary productivity is studied.Based on the absorption model and the fluorescence excitation spectrum to characterize its absorption coefficient,it solves the problem of single-band absorption coefficient instead of the total absorption efficiency of photosynthetically active radiation.The results showed that,compared with the results of photosynthetic oxygen evolution method,the relative errors of purebred algae before and after calibration were 3.17%and 1.83%,and the relative errors of blue and green algae mixed samples before and after calibration were 28.43%and 5.33%,respectively.After calibration,the accuracy of phytoplankton primary productivity measurement has been improved.(4)The auxiliary application function module of the rapid in-situ monitor for phytoplankton primary productivity is designed to improve the measurement accuracy of the field application.Combined with the PAR light quantum sensor,the ambient light analog adjustment circuit is designed to realize the free adjustment and simulation of different ambient light intensities;the photomultiplier tube automatic gain adjustment module is designed to realize the highly sensitive acquisition of the fluorescence signal of the algae samples with different concentrations;the multi-band is designed The LED excitation fluorescence spectrum acquisition module realizes the rapid acquisition of the algae excitation fluorescence spectrum.After testing,The response time of the instrument is 1.56 minutes,the accuracy is ?±9.69%,the precision is 4.86%,the detection limit is 0.138 nmol(e)/m3/s,and the measurement range is 0 nmol(e)/m3/s?1013 nmol(e)/m3/s,reproducible The reproducibility is 3.04%.In the Yellow Sea,the Bohai Sea,the South China Sea,the Arctic and other waters,the phytoplankton primary productivity in-situ monitor field measurement verification experiment was carried out,and the time and spatial distribution data of the phytoplankton primary productivity were quickly obtained,which verified the long-term stability and reliability of the instrument.