Studies On Photosynthesis Of Phytoplankton In China Sea

In this paper, modeling of primary production and in vivo chlorophyll fluorescence measurement are introduced into the study of the photosynthesis of phytoplankton in China Sea。1321 sets of chlorophyll data and 84 sets of product data were analyzed by nonlinear estimation, and the corresponding parameters that describing the chlorophyll vertical distribution and product-light curve were generated. Reference to the spatial distribution of the photosynthesis parameter, primary slope -α, the China Sea is separated into 9 provinces with different photosynthesis feathers. A primary production model that using light intensity and remote sensed chlorophyll concentration as input was developed, using the average values of the measured parameters of each province as the local parameter of the model.Analysis of the parameters shows that: The deep chlorophyll maximum (DCM) is marked in summer while is weak in winter, matching the phenomena that the thermocline appears in summer and disappears in winter. The maximum photosynthetic rate is related to temperature and nutrients, and it varies little through seasons. The primary slope of photosynthesis is most affected but the light history. It increases from spring to winter, opposite to the variation of seasonal variation of the irradiance. The photoinhibtion parameter presents the sensitivity of the phytoplankton to high light damages. It is low in summer and autumn, and is high in winter.Calculation result shows that the annual primary production of China Sea is about 6.4×108tC. The primary production in the north area of China Sea is higher then south area, and west area is higher then east area. The primary production maximum appears in summer for the north area while it appears in winter for the south area, and it appears in spring and autumn in the middle area, probably relating to the appearance of thermocline. The primary product calculated by the model is in some degree higher than that estimated by the measured primary production data. The errors may derived from the over estimation of the chlorophyll concentration for remote sensing of the type II water, and discounting the bottom topography, etc. Compare to the result of VGPM, our model is more close to the measured data. Cloud cover may lead to 25% variance of the primary production, and it is close to the real PAR situation when the cloud cover takes the value 0.5. We produced a application software based on the model, which can calculate the primary production just by chlorophyll concentration data. The improvement of the accuracy of the model relies on acquirement of more measured primary production data and more better remote sensing chlorophyll concentration data.In vivo chlorophyll fluorescence measurement is a rapid and facility method for tracing the photosynthesis activity of phytoplankton. In this study, we introduced the in vivo chlorophyll fluorescence measurement into the field investigation of phytoplankton photosynthesis status. By the dark-relaxation experiment, we developed the procedure for in situ measurement of phytoplankton F_v/F_m (photochemical efficiency, the maximum proportion that the energy used in the primary photochemical reactions in the total light energy absorbed by the light harvesting system) -a commonly used in vivo chlorophyll fluorescence parameter, by the OS5-AFM algae fluorometer. We made a high spatial-temporal investigation of phytoplankton photochemical efficiency in Jiaozhou Bay (2003-2004), and analyzed the relating factors. We made an attempt to calculate the primary production by F_v/F_m data.The investigation shows that, annual average of F_v/F_m for Jiaozhou Bay is about 0.37. It is highest in autumn and lowest in spring. The spatial variation of F_v/F_m is large in spring and small in summer. F_v/F_m in east part of the bay varies in a large range, and exhibit 4 peaks through the year. F_v/F_m in the west part of the bay is relatively stable, and exhibit 3 peaks through the year. The subregion of the bay that photosynthesizing most actively changed over seasons. The shifting mode is probably repetitious every year. The averages of F_v/F_m of each depth were not remarkably different, but the F_v/F_m values at bottom present a more evenly spatial distribution than that of the surface.By analyzing the dynamic of F_v/F_m and nutrients through the year, the phenomenon that the variation of F_v/F_m is lagging to the variation of inorganic nitrogen concentration in nature waters is first been discovered. In west part of the bay, F_v/F_m is more related to NH₄⁺ while in east part of the bay it is more related to NO₃^-. The lagging period may vary. The relativity between change rate of F_v/F_m and change rate of inorganic nitrogen concentration is higher than that F_v/F_m vs inorganic nitrogen concentration. It implicate that, even in waters in which inorganic nitrogen concentration is high so that the growth of phytoplankton is not limited by nitrogen supply, the variation of the concentration of nitrogen may still affect the photosynthesis activity of the phytoplankton.We tested the method to calculate the primary production by the parameters deriving from F_v/F_m and the water column primary production integral model. The result exhibit similar spatial and temporal distribution to that reported by presented literatures. But in quantity, our result is obviously lower. Acquirement of more synchronous F_v/F_m vs primary production data may improve the accuracy of the model. By this way, more rapid and convenient primary production measurement will be possible.