Profundal Testate Amoebae (Arcellacea) of Lake Superior and Lake Michigan

Sediment surface death assemblages of recent testate amoebae (Arcellacea) are reported from nine sites in Lake Superior and Lake Michigan. These are the first profundal sediment-water interface samples of testate amoebae described from either of the Great Lakes which provide valuable insight on deep-water, large-lake assemblages. Centropixid strains were present to abundant in shallower, nearshore sites (up to 66 m water depth). Assemblages at depths >40 m were dominated by Difflugia oblonga “tenuis.” The shallowest sample (26 m) was dominated by Centropyxis aculeata “discoides” and Difflugia oblonga “tenuis.” Over 100 tests per sample were observed from >100 m. Density of tests appears to be constrained by lithology rather than water depth. The deepest site (325 m) yielded low foraminiferal abundances. This pilot study provides a first step towards documenting the distribution of testate amoebae in the Great Lakes.