calculated as the mean of TSI(SD), TSI(Chl a) and TSI(TN). Huber et 

 al. regarded lakes with total N/total P values between 10 and 30 as 

 nutrient-balanced, and noted that nutrient-Chl a relationships were 

 different in these lakes than in nutrient-limited lakes. They 

 constructed new TSI expressions for total P (TSI(TPB) and total N 

 (TSI(TNB) for nutrient-balanced lakes, and defined TSI(AVG) for 

 these lakes as the mean of TSI(SD), TSI(Chl a), TSI(TPB) and 

 TSI(TNB). The TSI of Huber et al. is the only TSI developed 

 specifically for use in Florida lakes. 



All of the trophic state indices discussed above, however, share 

 in common their bias towards phytoplankton biomass and water- 

 column nutrient concentrations as the relevant indicators of primary 

 production in lakes, and they give no importance to the presence of 

 macrophytes. Porcella et al. (1980) constructed a multivariate index 

 based on Carlson's (1977) subindices and included a term derived 

 from percent-area coverage of macrophytes. Because Porcella et al.'s 

 TSI was developed for north-temperate lakes that are P-limited and 

 demonstrate hypolimnetic oxygen deficits during stratification, this 

 TSI might be inappropriate for use in Florida. The macrophyte term 

 also failed to quantify nutrients contained in macrophyte biomass as 

 other TSIs using water-column total P quantify the nutrients 

 contained in phytoplankton biomass. 



Canfield et al. (1983a) proposed a new approach to trophic state 

 classification of lakes that gave consideration to nutrients contained 

 in macrophyte biomass as well as to water-column nutrient 

 concentrations. They quantified the amount of P contained per unit 

 of dry weight in many species of macrophytes from 6 Florida lakes. 



