我国常用湖泊营养状态指数研究进展与展望OA北大核心CSTPCD

The eutrophication of lakes(including natural lakes and artificial reservoirs)and the associated algal blooms are global environmental problems,and the trophic state index is the most popular tool for quantifying eutrophication levels.However,there are obvious differences in ecological principle,applicability,etc.between the commonly used trophic state indices,and improper use may lead to misestimation of eutrophication levels and the associated risk of algal blooms,resulting in misalignment of lake pro-tection and restoration measures.Here,the ecological principle,commonalities,differences and sources of uncertainty of commonly used trophic state indices in China were reviewed in the current study.In general,the ecological principle of trophic level index in-cludes three types:1)Carlson type(e.g.trophic state index,TSI),secchi depth(SD)was considered as the key variable in Carlson type index,and doubled SD corresponds to the 10 points difference of the index,which hypothetically indicates doubled phytoplankton biomass changes.In addition,it is assumed that when SD reaches 64 m,it is recorded as an index value of 0;2)modified TSI type(e.g.modified trophic state index,TSIm),chlorophyll-a(Chl.a)is considered as the key variable in modi-fied TSI type,and 2.5-fold change in Chl.a corresponds to the 10-score difference that hypothetically indicated doubled phyto-plankton biomass changes.Meanwhile,it is assumed that when Chl.a reaches 1000 μg/L,the corresponding index score is 100;3)Trophic Footprint Index type(e.g.trophic footprint index,TFI),which also uses Chl.a as an indicator of algal biomass,with the e-fold of Chl.a corresponding to 10-score difference in the index,which hypothetically indicated doubled phytoplankton biomass changes.It was also assumed that 50 points of the index corresponded to a Chl.a of 10 μg/L.The corresponding base equations of the'key variable'(i.e.SD or Chl.a)were derived based on the above assumptions,and then both were'directly replaced'with empirical equation models between the key variable(SD or Chl.a)and the remaining variables to obtain the assessment equations for the derived parameter.According to the extension above,the commonality of the trophic level index is that the values of these indices increased with phytoplankton primary productivity and the associated algal risk.On the other hand,the differences between the Trophic Level Index were discussed from the perspective of 1)the dataset attributes and the method of obtaining the evaluation equation for the key variable,2)the statistical principle of obtaining the evaluation equation for the non-key variables,and 3)the way of setting the weights for the sub-indices.In terms of prospects,firstly,in order to improve the accuracy of evaluation,it is proposed to develop localised trophic state indices based on the three basic types mentioned above-as the current commonly used in-dices are characterised by a"one-size-fits-all"approach.Second,the ecological principle of the trophic level index is the theory of phytoplankton limiting factors.The differences in the trophic state index sub-indices(i.e.based on total nitrogen,TP,SD and Chl.a)can be used to identify the limiting factors of phytoplankton.It is suggested that research should be carried out on the mech-anism of the differences in the sub-indices,as these studies could guide cost-effective algal control efforts.Finally,since lake eco-systems are often degraded by other pressures in addition to eutrophication,it is recommended that studies be conducted on the mechanism of the integrated response of lake ecological health to eutrophication and other pressures,which can be used to formulate targeted restoration efforts to improve lake ecosystem health.The purpose of this review is not to complicate the use of the trophic level index,but to clarify its ecological principle and applicability,so as to provide a reference for the relevant personnel of lake eutrophication in using the index,and also to provide a scientific basis for the accurate quantification of trophic status and the accu-rate implementation of subsequent protection and restoration measures of lakes in China.