Study Of Remote Sensing Estimation Of Primary Productivity In Coastal Marine Waters Of Beibu Gulf

Ocean primary productivity refers to the rate of marine phytoplankton convert inorganic matter into organic matter through photosynthesis,which is a basis for evaluating the quality of Marine ecological environment and provides important reference for the development and planning of Marine environmental resources.In this study,the VGPM?Vertically Generalized Production Model,VGPM?is established to estimate the Ocean primary productivity in Beibu Gulf of Guangxi,and evaluate the estimation accuracy of the VGPM applied to such coastal?water.By assessing the accuracy of original model on the application of the coastal?water,calibrating the model parameters according to the results of sensitivity analysis of model parameters,and estimating the primary productivity in Guangxi Beibu gulf coastal water with the VGPM after parameters calibrated from 2009 to 2018,and analyzes some environmental factors influence on primary productivity respectively,the main conclusions can be followed as:?1?The estimation results are significantly higher when the VGPM uses the original parameters to estimate the primary productivity of coastal?water.The average values are much higher of the 14 sampling points in four sampling time as 873.04 mg C·m^-2·d^-1,1008.09 873.04 mg C·m^-2·d^-1,1089.09 873.04 mg C·m^-2·d^-1 and 1611.40 mg C·m^-2·d^-1.?2?The highest sensitivity parameter of VGPM is the concentration of chlorophyll a,followed by the Zeu,and the photosynthetic effective radiation and SST are weak due to their tiny fluctuations in one certain season.?3?Combined with baseline height and the measured chlorophyll-a,chlorophyll fluorescence data linear regression model is established,and the regression model R² is 0.821.The regression model of chlorophyll-a and chlorophyll fluorescence baseline height can effectively reduce the errors of chlorophyll a products from MODIS remote sensing data in Marine coastal water;The primary productivity of Beibu gulf in 2009 was estimated again based on the VGPM model after parameter correction,and the results shows that the average errors,mean variation,and standard deviation between remote sensing estimation results and measured data of primary productivity were significant improved.?4?The spatial and temporal distribution of primary productivity estimation results shows that:in spatial distribution,the high value area of primary productivity mainly appears in Qinzhou bay and Lianzhou bay.In the fall of2010,the primary productivity of Lianzhou bay area was the highest in the past10 years.In the spring of 2018,the primary productivity of Lianzhou bay area was the lowest in the past 10 years.Time distribution:in general,the primary productivity in the coastal waters of beibu gulf in the past ten years kept a stable development trend in each season,without significant fluctuations.?5?Correlation analysis of primary productivity and environmental factors shows that SST presents a positive correlation with the primary productivity;In winter and spring,photosynthetically active radiation has a positive correlation.In summer and autumn,due to the existence of light inhibition,excessive light intensity will cause certain inhibition to primary productivity.The correlation of nutrients indicates a seasonal demand of marine phytoplankton for nutrients in the Beibu gulf.The results of sea surface salinity correlation shows that the higher salinity water can inhibit the growth and reproduction of marine phytoplankton.