The Compare Of The Response Of Phytoplankton Community To Environment Based Three Phytoplankton Classifications

Phytoplankton communities are sensitive to environmental changes,which are a useful tool in assessment of water quality and ecosystem state.However,their responses to environment are different among classifications(with different number of taxa units,taxa abundance/biomass,and community traits).To understand the difference,the seasonal and spatial dynamics of phytoplankton communities under three phytoplankton classifications(phyla;morphology-based functional group,MBFG;and functional group,FG)and their responses to environment were compared with the investigated data from eleven subtropical reservoirs in southern China.The main results and conclusions are as follows:(1)The significant driving factors on the seasonal succession of phytoplankton communities are obviously different among the three classification methods based on redundancy analysis(RDA): 145 species of phytoplankton have been identified in Dashahe Reservoir,which belonged to 7 phyla,24 FGs,and 7 MBFGs;and 110 species of phytoplankton have been identified in Zhenhai Reservoir,which belonged to 7 phyla,25 FGs,7 MBFGs.The factors: transparency,dissolved nutrients,water temperature,and zooplankton grazing,showed obviously seasonality in both reservois.NO3--N was the significant variable explaining the community succession of FG and phyla,however,it was water temperature for the community succession of MBFG in Dashahe Reservoir.SD and TN was the significant variables explaining community succession of MBFG and phyla,however,no significant explaining variables was detected for the community succession of FG.(2)The significant factors contributing the spatial difference of phytoplankton communities are obviously different under the three classifications based Mantel test: 129 species of phytoplankton have been identified in the 8 reservoirs in eastern Guangdong,which belonged to 7 phyla,26 FGs,7 MBFGs.The 8 reservoirs were mesotrophic and their environment characterized with high temperature(32.6±1.1)? and low light bioavailability(Zeu/Zm was 0.48±0.28).The variance of dissolved nutrients contributed the mainly environmental differences between the 8 reservoirs.Among the 3 classification methods,only the phytoplankton community gradient of MBFG and phyla significantly correlated with environmental gradient,especially the gradient of p H value and PO₄^3--P concentration.(3)the key factors contributing the spatial gradient of the phytoplankton community in Gaozhou reservoir were obviously different based on redundancy analysis(RDA)and Mantel test: 130 species of phytoplankton have been identified in Gaozhou Reservoir,which belonged to 7 phyla,25 FGs,and 7 MBFGs.p H value,transparency,total phosphorus,dissolved inorganic nitrogen showed pronounced spatial gradient.The dissimilar of phytoplankton community of FG was greater than that of the phyla and MBFG.The correlation between environment and phytoplankton community of MBFG was higher than it of FG and phyla based RDA,and the importance of temperature,p H value,conductivity,NO3--N and PO43—P were pronounced different in explaining the gradient of the phytoplankton community under the 3 classifications.The R2 adj values and the explaining importance of conductivity,total phosphorus and total nitrogen were obvious differences under the 3 classifications based Mantel test.