Abstract

Conditions in James Lake vary from uncontaminated and nearly neutral pH conditions through most of the lake, to extremely low pH conditions (2.1 in places) contaminated with Fe, Al and SO4 adjacent to an abandoned pyrite mine near the lake outlet. Six assemblages representative of distinct arcellacean habitats were recognized in sediment-water interface samples collected in the lake using Q-mode Cluster Analysis. R-Mode analysis of this distributional data corroborates previous results indicating that arcellacean strains from within the same species are useful for discriminating environments.

Cucurbitella tricuspis dominates most samples and had to be deleted from analysis to determine benthic faunal relationships. This species is seasonally planktic and thus readily transported; it should not be considered in intralake studies. Arcella vulgaris overwhelmingly dominates extremely hostile low pH environments (<5.5) near the old mine site in samples where Shannon Diversity Index values of <1.000 are recorded. The highly variable pH in James Lake permitted the determination of precise boundary conditions for distribution of this species. These results indicate that Difflugia protaeiformis “claviformis” is an ideal indicator of industrial contamination under higher pH conditions. The D. protaeiformis “amphoralis” and “acuminata” strains are more closely linked to uncontaminated muddy substrates characterized by high proportions of diatoms, a probable important food source. The presence of Lesquerasia spiralis seems to be partially linked to substrate type with greater numbers typically found in coarser sediments.

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