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CHAPTER 4 

 DISCUSSION 



Dominant Environmental Variables and Scale of Analysis 



The purpose of this study was to identify diatom taxa that are 

 indicators of macrophyte presence in lakes. Despite an appropriate 

 sampling design, macrophytes were not found to be a primary 

 determinant of diatom assemblages. A trophic-state/pH/specific- 

 conductance environmental gradient was the principal influence on 

 the diatom communities. 



I sampled lakes along a wide gradient of macrophyte abundance 

 in order to develop predictive models with broad application for 

 inferring historical macrophyte standing crop, and by necessity I 

 transgressed the trophic-state gradient that is present among Florida 

 lakes. A negative correlation exists between macrophyte abundance 

 and water-column Chi a (Canfield et al. 1984) in Florida lakes. I also 

 observed a negative correlation between percent-area coverage of 

 macrophytes and water-column total P in the present study. Lakes 

 that were low in percent-area coverage (< 10%) were high in water- 

 column nutrients, whereas several lakes that were high in percent- 

 area coverage (>80%) were low in water-column nutrients. 



pH, trophic state and specific conductance were mutually 

 correlated in this study as in other studies of Florida lakes (Canfield 



90 



