Arcellinida (Testate Lobose Amoebae) as Sensitive Bioindicators of Arsenic Contamination in Lakes

Arcellinida (testate lobose amoebae) are sensitive to arsenic (As) contamination from historic gold mining in Canadian subarctic lakes. Partial redundancy analysis revealed that As (9.4%) and S1 (labile organic matter, 8.9%) were the most important contributors to variance in faunal distribution. Arcellinida are important intermediary food web components in lacustrine environments. Microbes are their primary food source and elevated As-levels are known to suppress microbial growth (S1). The observed correlations are likely to be related to As-destabilization of Arcellinida microbial food supplies. To assess the utility of arcellinidans as tracers of temporal variation in As, we analyzed a freeze core from Frame Lake in the city of Yellowknife, which requires remediation following a steep decline in water quality through the 1960s that left it dead. Land-use activities in the area of the lake are well documented but little information is available regarding their impact on the lake itself. Geochemical, sedimentological and arcellinidan analysis showed that the system was non-depositional from the mid Holocene until ~1962 when the lake began to rapidly infill with highly As contaminated sediments. Since the early 1990s runoff from the catchment, and reduced lake circulation associated with installation of a causeway with rarely opened sluiceways at the only outlet, has caused eutrophication.