Mollusca of Six Low-Alkalinity Lakes in Ontario

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Abstract
In 1980 and 1981, we sampled the molluscs of six Ontario lakes with low alkalinity concentrations. Contrary to previous reports of rarity or absence of molluscs in low-alkalinity waters, we showed that there was no consistent difference in the number of species present in these lakes, across a limited range of alkalinity (0.24–3.17 mg∙L−1). It is possible that molluscs are more dense in lower alkalinity lakes, due primarily to large numbers of Pisidium casertanum and P. ferrugineum found there. Significant differences between mollusc densities in two intermediate-alkalinity lakes indicate that factors other than alkalinity may have affected mollusc distributions. The unionid clam, Elliptic complanata, was found in two lakes with mean alkalinities of 0.41 mg∙L−1.