Benthic Metrics a.1. Significant Environmental Variables (R2) a.2. Significant Environmental Principal Components*
Taxonomic Richness -Total TUs*** (0.25) -PC1***(0.29)
% Dominant Taxon +Total TUs*** (0.31), +Vegetative protection (0.11), -Lambda-cyhal. (0.11), +Deltamethrin  (0.08) +PC1***(0.28)
Ephemeroptera Taxa +Frequency of riffles/bends ** (0.32) +PC2** (0.16)
EPT Taxa +Embeddedness ** (0.30) +PC2** (0.18)
EPT Index (%) -Permethrin (0.20), +Cypermethrin (0.18), +Embeddedness ** (0.16) NS
Shannon Diversity -Zn *** (0.21), +%Fines (0.11) -PC1*** (0.18)
* The environmental variables with the largest loadings for the environmental principal components (proportion of variance explained by PCs are in parentheses) are: PC1 (0.49) = +TUs for all pyrethroids, +Mercury to TEL and +Zinc to TEL; PC2 (0.12) = +Total Score, +Embeddedness, +Frequency of riffles/bends, +Sediment deposition, +Velocity depth regimes, and -%Fines; PC3 (0.10) = -%Canopy Cover, +Bank Stability, +Cadmium to TEL, +Lead to TEL, +Zinc to TEL, and +Copper to TEL; PC4 (0.08) = +Nickel to TEL, +Arsenic to TEL, +Chromium to TEL, and +Total metals to TEL; PC5 (0.05) = -Riparian vegetative zone, +Epifaunal substrate/available cover, +%Boulder, -Channel alteration, and +%Cobble; PC6 (0.04) = +Channel Flow.
** Variables that remained significant after the toxicant-loaded principal components (PC1, PC3 and PC4) were forced into the stepwise regressions prior to the testing of the habitat variables (Model 1 regression confirmation; see text for details).
*** Variables that remained significant after the habitat principal components (PC2, PC5, and PC6) were forced into the stepwise regressions prior to the testing of the toxic variables (Model 2 regression confirmation; see text for details).
Table 12: Results of stepwise multiple linear regression models for the three year data sets: a.1. benthic metrics versus toxicity units for pyrethroids, habitat metrics, and metals to TEL ratios for Arcade Creek; and a.2. benthic metrics versus principal components of the environmental data for Arcade Creek; b.1. benthic metrics versus toxicity units for pyrethroids, habitat metrics, and metals to TEL ratios for the three Salinas streams; and b.2. benthic metrics versus principal components of the environmental data for the three Salinas streams. Only variables that were significant at α=0.01 were included in the models (NS= not significant; NA=not analyzed because few, if any, of the samples had the benthic metric present). The direction of the relationship for each significant variable is indicated (+ = direct; - = inverse), as is the contributed R2 value.