85 



diatom taxonomic groups into an axis constrained by percent-volume 

 infestation. When axis scores for the 29 survey lakes were regressed 

 with percent-volume infestation values using the SAS GLM 

 procedure (SAS Institute, Inc. 1985), the following predictive 

 equation was obtained: 



percent-volume infestation = 33.8+ 0.7(Axis 1) 3.7 



r2 = 0.600, p < 0.001, n = 29 

 where Axis 1 is the sum of products of eigenvectors and percentages 

 of the 47 diatom taxonomic groups. 



When canonical correspondence was invoked to produce 

 eigenvectors ordinating the 47 diatom taxonomic groups into an axis 

 constrained by percent-area coverage, CANOCO returned eigenvectors 

 ordinating 45 of the taxonomic groups (Table 10). Tabellaria 

 fenestrata and T. floccolosa may have been eliminated by CANOCO in 

 this ordination because of under-representation. Axis scores for the 

 22 survey lakes with percent-area coverage values were regressed 

 with percent-area coverage using the SAS GLM procedure (SAS 

 Institute, Inc. 1985). The resulting equation was: 



percent-area coverage = 53.6 - 0.5(Axis 1) 3.8 



r2 = 0.447, p < 0.001, n = 22 

 where Axis 1 is the sum of products of the percentages and 

 eigenvectors of the 45 diatom taxonomic groups shown in Table 10. 



A New Predictive Model for Water-Column Total P 

 Because inferences from Whitmore's (1989) TSI(TP) predictive 

 model cannot detransformed to yield total P values for WCP (Canfield 

 et al. 1983a) estimates, a new model is presented here using the 



