Preparation And Mechanism Of Efficient Modified Clay Controlling Phaeocystis Globosa Blooms

Phaeocystis globosa is a harmful algal bloom(HAB)species that is widely distributed around the world.Importantly,Phaeocystis blooms can impact the safety of nuclear power stations because large colloidal colonies can block the filters of nuclear power plants.How to remove P.globosa in emergent situation was important applications in the field of marine environmental protection.Modified clay(MC)technology is currently one of the most common methods to mitigate HABs in the world.However,previous research has been conducted mainly on HABs formed by single algal cells(as opposed to colonies).At present,no studies have explored the control mechanism of this particular morphology and structure of P.globosa,nor have targeted formulation improvements been adopted to explore a more effective MC system for this particular HAB-causing organism.Based on previous research,this study used P.globosa as the research object,and the density of cells and colonies,polysaccharide content,antioxidant system.The potential mechanism of MC inhibiting the growth and colony formation of P.globosa was analyzed from physiological and biochemical and molecular biological perspectives.This study provides important evidences for the control and mitigation of P.globosa blooms with MCin an emergency.The main findings are as follows:(1)The oxidized composite modified clay had the best effect on the elimination of P.globosa,which could efficiently remove P.globosa cultured in laboratory and in field.The removal efficiencies of MC to P.globosa was over 90%at a dose of 0.2 g/L.The addition of modified clay has no adverse effect on the water quality,but caused the DIP levels drop.(2)The results showed that oxidized composite modified clay could not only effectively remove P.globosa but also could inhibit the growth of residual algal cells and the formation of new colonies.Compared with those of the control,the SOD activity,CAT activity and MDA content of the residual algae were significantly increased,indicating that MC stimulated the accumulation of ROS in the algal cells and caused oxidative stress,which affected the normal growth,division and colony formation of P.globosa.The application of MC severely damaged the photosynthesis system of P.globosa,resulting in decrease of Fv/F_M and?PS?.(3)MC treatment resulted in differential gene expression in residual cells.In addition,numerous differentially expressed genes were enrich-edin the carbohydrate metabolism,physiological processes,cell structures related to stress adaptation and detoxification.These results illustrated that physiological processes were affected in residual P.globosa after treatment with MC.Particularly,genes encoding glycosaminoglycan degradation were up regulated at 24 h after MC addition,indicating that MC could accelerate the degradation of polysaccharides and has a certain ability to break the colonies.In conclusion,this study tested and developed the efficient modified clay,OXI-MC,which can efficiently remove the cells of P.globosa and break the colonies.The P.globosa algal biomass removal efficiencies after 3 h over 90%at a dose of 0.2 g/L,and the number of colonies was greatly reduced.The results of our study clarified that OXI-MC could effectively inhibit the growth and colony formation of P.globosa by collision and flocculation,releasing active substances,causing oxidative stress,reducing photosynthesis activity,accelerating the degradation of polysaccharides,preventing a second outbreak of HABs.This study provides important evidences for the control and mitigation of P.globosa blooms using MC in an emergency.