Lacustrine Arcellinida (Testate Lobose Amoebae) as bioindicators of arsenic concentration within the Yellowknife City Gold Project, Northwest Territories, Canada

Abstract Arcellinida (testate lobose amoebae) were examined in near-surface sediment samples from 30 lakes located within the Gold Terra Resource Corporation (GTRC) Yellowknife City Gold Project, Northwest Territories, Canada, to assess the applicability of using the group as a robust tool to assess Arsenic (As) contamination. Lake contamination by As is of concern in the Yellowknife area because it is derived from geogenic (bedrock) and anthropogenic sources (legacy pollution from former mining operations, particularly the Giant Mine [1948–2004]). Statistical multivariate analyses (cluster analysis, non-metric multidimensional scaling [NMDS], and redundancy analysis [RDA]) were performed on geochemical (inductively coupled plasma mass spectrometry [ICP-MS]) and organic (loss-on-ignition) data to identify geochemical and hydrogeological controls on the arcellinidan distribution in the lakes. Three distinct faunal assemblages were identified using Cluster analysis and NMDS: 1) Elevated Arsenic Assemblage (EAA; Approximately Unbiased (AU) p-value = 97 %; median As =272.4 mg/kg, range = 42–1353 mg/kg ; n = 9); 2) Centropyxid-Dominated Assemblage (CDA; AU p-value = 87 %; median As =169.7 mg/kg, range 60–233 mg/kg ; n = 9); and, 3) Difflugiid-Dominated Assemblage (DDA; AU p-value = 95 %; median As =61.3 mg/kg, range = 16–316 mg/kg ; n = 12). Six statistically significant controls on assemblage structure were identified using RDA. These were As, calcium, iron, strontium, water depth, and total organic carbon (Arcellinida variance explained = 36.2 %) — As is the most significant control (12.2 %; p-value