Benthic metrics a.1. Significant Variables (R2) a.2. Principal Components Tolerance Value +Mercury *** (0.39) -PC2**(0.20) % Tolerant Taxa (8-10) +Mercury*** (0.53) -PC2**(0.24), + PC6**(0.14) +PC1*** (0.11), % Collectors/Filterers +Embeddedness (0.17), -Velocity depth regimes (0.11) NS % Collectors/Gatherers -Embeddedness** (0.30) -PC2** (0.21) % Grazers +Total TUs*** (0.68), -Riparian vegetative zone** (0.11) +PC1*** (0.57), +PC5** (0.12) % Predators +Lead *** (0.29) NS % Shredders NA NA Abundance (#/sample) NS NS Regression Models for Arcade Creek. ** 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 12a: Regression models for Arcade Creek.