Study On Environmental Adaptability And Nutrients Uptake Of Gracilaria Edulis

Because of the rapid development of aquaculture industry,a large amount of nitrogen and phosphorus nutrients are discharged into the marine and polluted the costal water body,which influenced stability of marine ecosystem and health of biomass.Costal environmental governance is a hot spot currently.Seaweeds can be used for ecological remediation in seawater for they are able to remove nitrogen and phosphorus nutrients efficiently.Gracilaria edulis are mainly distributed in tropical and subtropical marine area,which have a high economical value that could be used as industrial raw materials of agar.In order to explore the different environmental and nutrients condition adaptability of G.edulis and its removal efficiency of nutrients,the effects of temperature and irradiance interaction and nutrient conditions on growth,physiological and biochemical index of G.edulis were studied.In addition,to investigate the potential of nutrients removal of G.edulis in marine aquaculture,the effects of culture density on characteristic of nutrients uptake were discussed in this paper.The main results are as follows:（1）To explore the suitable environmental conditions for the growth of G.edulis,the effect of temperature（20,24,28,32,36℃）and irradiance(50,100,150μmol·m^-2·s^-1)interaction on growth,physiological and biochemical indexes of G.edulis were studied.The results shows that the suitable temperature and irradiance for the growth of G.edulis is 24-32℃and 100-150μmol·m^-2·s^-1.The most suitable temperature and irradiance interaction group is 28℃and 100μmol·m^-2·s^-1.The relative growth rate,biochemical index and antioxidant properties were optimal at these conditions.（2）To explore the suitable nutrient conditions for the growth of G.edulis,the effects of concentration of total inorganic nitrogen（48,96,144,192,240μM）,ratio of N and P（1:1,5:1,10:1,20:1,50:1）and NO₃^--N:NH₄⁺-N:NO₂^--N（1;1:1,10:5:1,10:1:5,5:1:10,5:10:1,1:10:5,1:5:10）on the growth and biochemical components of G.edulis were studied.The results shows that the relative growth rate,biochemical index and antioxidant properties of G.edulis are optimal when the concentration of total inorganic nitrogen is 144μM,ratio of N and P is 10:1and 20:1,NO₃^--N:NH₄⁺-N:NO₂^--N is 10:5:1 or 5:10:1.（3）To explore the suitable culture density for remediation on eutrophication of G.edulis,the effects of culture density on removal efficiency of N and P,content of dissolved oxygen and p H in water body were studied.The results shows that the optimal culture density is 3.0g·L^-1,while the removal efficiency of N and P,increasing of dissolved oxygen concentration and p H value is the highest.The study shows that G.edulis can adapt to the high water temperature environment.It is feasible for the cultivation of G.edulis in costal area of subtropical areas.Besides,the characteristic of nutrients uptake of G.edulis is great.The study provides theoretical basis for cultivation and potential of ecological remediation of G.edulis.