l'..:X. 



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66 



variables, 4 were significant. A cluster that was composed of the 

 taxon C alone is sp. A was significantly correlated with emergent 

 biomass, but this correlation was driven by a single datum point 

 because of the unusually high percentage of this taxon in Crooked 



|(^J '. Lake. Another cluster consisted of Fragilaria brevistriata and 



Gomphonema spp. (S-GOMA) and was signifcantly correlated with 

 percent-volume infestation. This correlation did not appear 



^^fe : meaningful because F. brevistriata was represented by only two data 

 points, and G. spp. was correlated with percent-volume infestation 

 only because of anamalously high values in Lake Carr. In addition, F. 

 brevistriata and G spp. showed different slopes over the range of 

 percent-volume infestation. A third cluster, which seemed 



#; spuriously correlated with emergent biomass, consisted of two 



euplanktonic and two periphytic taxa. Asterionella spp. (S-AST) and 



vxv Aulacoseira islandica were the two euplanktonic taxa in this cluster 



,/; and they showed high values only in Crooked Lake. Tabellaria 



flocculosa and T. fenestrata were the periphytic taxa in this cluster 

 and their slopes were different over the range of emergent biomass. 



v|v A fourth cluster was positively correlated with floating-leaved 



biomass (r = 0.554, p = 0.008, n = 22) and contained 9 taxonomic 

 groups (Appendix 3.7), seven of which were euplanktonic. These 

 taxa were used as independent variables in a stepwise regression 

 procedure to predict floating-leaved biomass. 



When the clustering procedure was repeated partialling out the 

 effects of TSI(AVG) and pH, a cluster composed of the 7 euplanktonic 

 taxa last mentioned was again positively correlated with floating- 

 leaved biomass. Four clusters were still significantly correlated with 



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