小浪底水库绿藻的鉴定及其对不同氮素的生长与光合响应OA

Xiaolangdi reservoir is the largest water conservancy hub in the middle reaches of the Yellow River and serves as an important water source.Water quality in the reservoir thus affects the production and life quality of residents in the surrounding area.In this study,three dominant green algae were isolat-ed from Xiaolangdi reservoir and identified as Ankistrodesmus falcatus,Scenedesmus quadricauda and Coelastrum microporum by morphology and molecular identification using the 18S rDNA sequence.Sodi-um nitrate(NaNO3)and ammonium chloride(NH4Cl)were used as nitrogen sources,and we measured the effects of these two forms of nitrogen(NO3--N and NH4+-N)at different concentrations(0,0.5,1.5 and 10 mg/L)on the growth and photosynthetic performance of the three green algae species.The aim of the study was to provide reference for monitoring and protecting the water quality of Xiaolangdi reservoir.The three species of green algae responded differently to the different forms and concentrations of nitro-gen.Increasing the nitrogen concentration promoted the growth of all three algal species,and the algae density of A.falcatus cultured with NH4+-N was 1.08 times that cultured with NO3--N.The other two algal species preferred NO3--N and the respective densities of A.falcatus and C.microporum were 1.76 and 1.15 times higher with NO3--N than with NH4+-N.Overall,the photosynthetic rate increased with N-con-centration for all three algal species,but A.falcatus in the stable stage exhibited higher photosynthetic efficiency(YⅡ:0.275)at the low NH4+-N concentration,123.3％higher than in the acclimation stage.Further,A.falcatus exhibited lower non-photochemical quenching(NPQ:0.554)at the low NO3--N con-centration,83.3％of that during acclimation,and the initial slope(α:0.237)of the growth curve at the medium NO3--N concentration was 185.2％higher than during acclimation.S.quadricauda grew well on-ly under eutrophic conditions(high N-concentration),while the lower N-concentrations strongly reduced growth and photosynthesis,with all photosynthesis parameters significantly lower except for the maxi-mum photochemical efficiency(Fv/Fm).During the stable phase,the YⅡ value(0.095)in the control group was only 31.7％of that during the acclimation phase.C.microporum had a relatively wide adapta-tion range to nitrogen concentration but was more sensitive to changes in nitrogen concentration.During the stationary phase,the maximum electron transport rate(ETRmax:6.47)in the low NO3--N concentra-tion group was only 14.1％of that during the acclimation phase,and all parameters changed gradually as nitrogen concentration increased.These results provide information that is useful for managing water qual-ity in Xiaolangdi reservoir.