79 



shows a slight random error, but a lower total error term. The best 

 model for predicting percent-volume infestation (PVI) from 

 sedimentary concentrations of diatom groups is therefore: 



PVI = 36.960 - 4.2171og(ACHEX) + 7.8331og(STAUPH) - 



3.641 log(SYNFILEX) 3.2 



R2 = 0.519, p < 0.001, n = 29 

 where values for the 3 taxa, whose acronyms are defined in 

 Appendix 1, are expressed in valves g-^ dry weight of sediment. 

 The adjusted R2 value for this model is 0.461. 



The stepwise procedure was applied to log-transformed annual 

 accumulation rate values for 17 diatom taxonomic groups (Appendix 

 3.3). The best model utilized 2 diatom taxa and showed an R2 of 

 0.312. The adjusted R2 for this model was 0.259. The model was 

 less robust than the model based on log-transformed sedimentary 

 diatom concentrations. 



Percent-Area Coverage 



Eleven diatom taxonomic groups (Appendix 3.4) selected from 

 plots were used in the stepwise procedure to construct models 

 predicting percent-area coverage from diatom percentage data. The 

 best model, as determined from Cp values was: 



percent-area coverage = 27.294 + 3.971(S-CYM) -i- 0.871(S- 



FRUSRH) + 50.967(STAUPH) 3.3 



R2 = 0.502, p = 0.005, n = 22 



where values for the 3 taxonomic groups, which are defined in 



Appendices 1 and 2, are expressed as a percentage of each diatom 



