The Impact Of Thermal Discharge By Power Plant On Phytoplankton Communities

In recent decades,the numbers of power plants have been greatly increased along the coastal areas worldwide.The natural seawater pumped from adjacent areas is used to cool power plant unit,after which,the cooling water will be discharged into the sea.The temperature of cooling water is greatly higher than the adjacent sea areas,as well as co chloride,which can influence the distribution of the phytoplankton community structure.At present,due to the needs of economic development,China has established a large number of power plants in the coastal areas.The ecological impact,especially the disturbance of phytoplankton community,by cooling water,is still limited along the Chinese coasts.This study focused on the impacted areas of cooling water from the Daya Bay Nuclear Power Station(DBNP)and Laizhou Power Plant(LZPP).Bimonthly investigation was carried out from April 2017 to February 2018 for the DBNP,and from May 2018 to January 2019 for LZPP,respectively.The phytoplankton samples were collected and counted by microscopy.The photosynthetic pigments were determined by high performance liquid chromatography.The Chemical Taxonomy software(CHEMTAX)was used to calculated the contributions of different phytoplankton assemblages to chlorophyll a.The main results are shown as follows:Daya Bay Nuclear Power Station 1)the effect of discharge of cooling water caused the water temperature to rise obviously in June,compared with that in autumn and winter.Thermal discharge caused stronger stratification of water column in the warm months than the cold ones.2)The abundance of diatoms was negatively correlated with water temperature in summer,autumn and winter.The abundance of dinoflagellates was positively correlated with water temperature in April,October and December.In addition,stratification of water column caused by thermal discharge might provide a good environment for the accumulation of Dinophysis;Laizhou Power Plant 1)The increase of water temperature caused by thermal discharge is obvious within about 500 meters,especially for that in July.2)Except for July,the water temperature and cell abundance of diatoms and dinoflagellates showed a negative correlation,and the effect of temperature on dinoflagellates was greater than that of diatoms.There was a positive correlation between Shannon Weiner index,Pielou index and temperature;3)The correlation between the biomass of each phytoplankton functional group(calculation by CHEMTAX)and temperature is different.The biomass of Dinoflagellates,Cyanobacteria,Chlotophytes are negatively correlated with temperature.In May,September and January,dinoflagellates biomass and temperature showed a negative correlation.While in July and November,there was a positive correlation between them.