Integrated Impact Of Thermal Discharge On Plankton Community Metabolism In Daya Bay

Marine ecological effects induced by thermal discharge of nuclear plants in Daya Bay(DYB)are attracting increasingly attention.Based on in situ investigations and laboratory simulating experiments,plankton community metabolism,primary producer size structure and other parameters in thermal discharge area of DYB were studied in August 2016 and January,August 2017.The effects of nutrients input were explored in order to understand the response mechanism of plankton to eutrophication.1.In situ investigation revealed that values of gross primary production(GPP),community resprition(CR),net primary producton(NCP),primary production(PP),bacterial prodciton(BP)and chlorophyll-a were higher in context of optimum temperature in thermal discharge areas between summer and winter,while and vice versa in extreme high temperature(36.0?)or high temperature(31.4?),which existed obvious inhibition of hyperthermia,water specimens were in a heterotrophic metabolic equilibrium state.2.Simulated warming experiments indicated that GPP,CR,NCP,PP,BP and chlorophyll-a of plankton significantly increased and then decreased with warming,particularly at the extremely high temperature(38?).Metabolic process of plankton community was inhibited remarkably in summer.With the prolonging of incubating time,primary production and respiratory metabolism of plankton will promoted by heating effect,finally incubating water reached in an autotrophic metabolic equilibrium state.On the contrary,values of parameters for plankton community respiration increased gradually with the rising temperature and prolonging of incubating time in winter.Warming obviously facilitated the community metabolism and primary production of plankton community,and the incubated water showed autotrophic metabolic state as well.3.Interactive simulating experiments of temperature,and nutrient enrichment showed that both temperature rise and nutrient input could promote the value of GPP,CR,NCP,PP,BP and chlorophyll-a remarkably,which also showed as autotrophic metabolic state of plankton community in the whole incubating stage,when the incubating time was prolonged.Values of parameters for plankton community metabolism and primary production showed significant seasonal differences,which affected by warming and nutrient input.Effect of chlorophyll-a,GPP and NCP on nutrients input was more remarkably than that of temperature.GPP,NCP,PP and BP were significantly inhibited in early cultured stage(24h)under extremely high temperature conditions,while sensitivity of the relative planktonic parameters to the temperature response were higher than nutrients in winter.Both warming and nutrients input may promote or inhibit planktonic community metabolism and primary production process,which will lead to miniaturization in size structure of phytoplankton and the tiny size phytoplankton dominated(<20?m).Moreovre,carbon metabolism balance of planktonic community,energy flow and material cycle on food web would be affected,which will impair marine ecosystem stability,biodiversity and marine environment quality and fishery resource output.Thus,It is of great significance for management of marine ecosystem,prevention and control of aquatic ecological disasters by studying the response of plankton community metabolism and primary productor size structure to warming effect and nutrients input.