Study On The Effect Of Small-scale Turbulence On The Cell Physiology Of Synechocystis Sp.

Landscape water is an important part of the landscape,it not only has a strong ornamental function,but also can regulate the ecological environment and micro climate,water quality related to water ecological safety and sustainable development.However,in recent years,eutrophication of water bodies seriously affects the water quality of landscape water bodies.Turbulent disturbance is one of the causes of the breakout of water bloom,it is generally believed that turbulence changes the position and distribution of microalgae in the water column,minimizes sinking of individuals,increases advective transport of nutrients to the cell surface,regulates light accessibility and photosynthesis intensities,and affects the encounter possibility between microalgae and predators.In recent years,more and more studies have found that turbulence has direct effect on microalgae cell biology.In this study,the pattern species of Cyanobacteria was set as the experimental material.Through batch culture experiments,the cell biology of Synechocystis sp.under a gradient of turbulence intensity was determined,including the specific growth rate,photosynthetic activity,cellular elemental composition,phosphorus uptake rate,cell morphology,composition and content of the extracellular polymer,and Zeta potential and sedimentation rate.The thickness diffusion boundary layer was explored and the relationship between the changes of EPS content and the physical and chemical properties of cell surface were calculated.Preliminary research results are as follows:1.Turbulence promote the growth of Synechocystis significantlyThe biomass grown under turbulence is always higher than the still condition.And the specific growth rate increases with the increase of turbulence.The maximum biomass under still condition is 1.24,and the maximum biomass under turbulence is 2.38,almost 2-fold of the still condition.2.No significant effect of turbulence on the photosynthesis activity of Synechocystis sp.Photosynthesis is the basic physiological processes of microalgae,and photosynthesis activity is the basic characteristics of its physical state.In the study,the photochemical efficiency,maximum electron transport and the Chlorophyll a content of Synechocystis sp.under the turbulence have no significant changes.It indicates that there is almost no effect of turbulence on the photosynthesis and there must be other physiological mechanism.3.Turbulence changes the cellular elemental compositionThe change of cellular elemental composition shows the adaptation strategy of Synechocyslis sp.to turbulence.Cellular total carbon and cellular total phosphorus increase with the increase of the turbulence intensity,and the cellular total nitrogen is decreased.Carbon nitrogen ratio shows a growth trend,and nitrogen phosphorus ratio shows a decreasing trend.4 Synechocystis sp.cell turn smaller under turbulenceTurbulence has obvious effect on the cell size of Synechocystis sp..Cell size decreases as the turbulence increases,and the specific surface area of the cell increase as the result.It is benefit for cell to absorb the nutrient elements and discharge the metabolites.5 Effect of turbulence on the extracellular polymeric substance content and composition of Synechocystis sp.The results showed that,with the increase of turbulence intensity,EPS content decreased,the absolute value of Zeta potential reduced,and the sedimentation rate slightly rised.Because EPS is composed of macromolecule,can block the absorption of nutrient elements,so nutrient uptake rate is increased along with the reduction of EPS.Above all,the possible mechanism that turbulence effects the growth of Synechocystis sp.is that,shear stress produced by turbulence take away part of EPS from the cell surface.Reduction of EPS content improved the nutrient absorption rate.At the same time,Cells adjust their own size under the stimulus mechanical signal.The smaller the cell is,the bigger the specific surface area.To a certain extent,both the above two,improve the nutrient uptake rate and transmission of metabolites.The improvement of nutrient element absorption rate,promote the growth of the Synechocystis sp.directly.