Study On Physiological Property Changes And Nutrient Metabolism Characteristics Of Blue-green Algae In Turbulent Environment

After the impoundment of Three Gorges Reservoir,algal blooms occurred in tributaries frequently,It has a serious impact on water environment safety of the reservoir area.Many opinions suggest that hydrodynamic force changes in tributaries Bay caused by impoundment of Three Gorges Reservoir is the main cause of algal blooms.But there is still no clear conclusion on how hydrodynamic conditions affected the growth of dominant algal and induced bloom.A preliminary analysis of the Three Gorges Reservoir Flow suggested that the water body of the tributary is in a turbulent state,however,There is no definite conclusion on whether physiological activity and nutrient metabolism characteristics of typical water bloom algae was affected by turbulent environment of tributary.In this paper,the common dominant species in tributaries of reservoir(Anabaena flos-aquae)was experimental subjects,a continuous flow reactor was used for chemostat culture,stable algae in different growth rates(0.1d-1,0.3d-1,0.6d-1)was obtained.The research is objective to study the physiological changes of Anabaena under different turbulence conditions(the gradient of turbulent dissipation rate varies between 0-3.03×10-2m2·s-3)in stable growth conditions,in order to clarify the physiological change mechanism of algae under the combined effects of various complex factors of natural water bodies and provide basic research support for the mechanism of algal bloom,it provides a new idea for the prevention and control of water bloom in eutrophic water.The main conclusions are as follows:Energy dissipation rate in 0-3.03×10-2m2·s-3(1)Under certain turbulence intensity,turbulence disturbance promotes the cell division and growth of Anabaena anabaena.At a higher rate of growth(0.6d-1),the effect of turbulence on the growth of Anabaena Anabaena was more significant.(2)Under certain turbulence intensity,turbulence disturbance influences the photosynthetic oxygen evolution of algal cells,the greater the disturbance intensity,the higher the maximum oxygen release rate;(3)When the growth rate is 0.1d-1,with the increase of disturbance intensity,the Rd(dark respiration rate)of algal cells showed a tendency to increase,there was no significant change in Ik(saturation light intensity),When the intensity of disturbance reached 0-3.03×10-2m2·s-3,a(the photosynthetic efficiency)was significantly higher than that of the control group;When the growth rate was 0.3d-1,the Rd of algal cells increased with the increase of disturbance intensity,when the disturbance intensity increased to 1.54×10-2m2·s-3,the Ik was significantly greater than that of the control group,only when the disturbance intensity is 1.54×10-2m2·s-3,a was significantly lower than the control group;When the growth rate was 0.6d-1,both Rd and a first increased and then decreased,and reached the maximum at 1.54×10-2m2·s-3,when the disturbance intensity increased to 3.03×10-2m2·s-3,the Ik was significantly greater than that of the control group;(4)The turbulence disturbance does not affect the important enzymes in photosynthetic strategy of Anabaena Flos Anabaena——CA(carbonic anhydrase)and Rubisco(Ribulose bisphosphate carboxylase oxygenase),and photosynthetic activity of algal cells was not affected;(5)In different turbulent environments,the size and morphology of Anabaena Flos have changed.When the dilution rate was 0.1d-1,the length of the algal filament decreased with the increase of the perturbation intensity,when the dilution rate was 0.3 and 0.6d-1,the length of the algal filament increased with the increase of the perturbation intensity.The specific surface area of algae cells showed a single peak change with the change of disturbance intensity,first increased and then decreased,and reached the maximum at 0.71,1.54 and 0.71×10-2m2·s-3 respectively;(6)In turbulent environment,the contents of C,N and P in the Anabaena Anabaena were significantly changed.The content of C decreased with the increase of the perturbation intensity,and the main reason was the decrease of the synthesis of fine inclusion macromolecules(sugars and lipids);The content of N and P basically increased first and then decreased,and turbulence disturbance promoted the absorption of N and P,when the turbulence intensity is continuously strengthened,the absorbed N and P are mainly used for the rapid division and growth of cells,storage part reduced;(7)Combined with the analysis results of intracellular biological macromolecules in the same period,it can be concluded that the turbulence disturbance mainly changed the absorption and distribution of nutrients,then changed the synthesis of organic compounds such as sugar,protein and lipid.With the increase of turbulence intensity,the total sugar content of algal cells were decreased,and the total protein content of algae cells was on the rise,Lipdi content of algae at lower growt rate showed a downward trend,at higher growth rate showed a upward trend.Based on the above results,the turbulence disturbance does not affect the physiological activity of Anabaena by its photosynthetic activity and carbon fixation strategy,but mainly through the influence of nutrient absorption and distribution,changed the intracellular sugar,protein,lipid and other organic synthesis,the changes of cell size and morphology,photosynthesis and oxygen evolution were induced,changes in cell size and morphology,in turn,affect nutrient absorption.Differences in shape,size and physiological structure of algae at different growth rates led to the difference of physiological effects of turbulence on algal cells at different growth rates.