Whole lake addition of cadmium-109: radiotracer accumulation in the mussel population in the first season

Cadmium with the radiotracer 109Cd was added to the epilimnion of Precambrian Shield Lake 382 in the Experimental Lakes Area, northwestern Ontario to monitor pathways of Cd from water to abiotic and biotic components, to quantify Cd accumulation and distribution in biota and to evaluate adverse biological and ecological effects. This experiment will permit evaluation of the adequacy of the water quality guideline of 0.2 μg Cd l −1 in protecting aquatic life in softwater lakes. As part of the whole-lake experiment, we monitored the activities of 109Cd in various body parts of the floater mussel Anodonta grandis grandis to determine accumulation and distribution of Cd. Additions of Cd from 23 June to the end of October 1987 (a total of 900 g Cd and 89 mCi of 109Cd) increased the total [Cd] in the water from 1.6 to about 85 ng l −1. Cadmium-109 was accumulated in body parts of the mussels, in increasing concentration: mantle < foot < gill < visceral mass < kidney. After 4 months exposure to the increased water [Cd], the mussels had increased body burden of Cd by an estimated 5–9 times. At the latter increase, the population of 7330 ± 2100 mussels in the lake contained an estimated 0.011–0.020% of the added 109Cd.