Arcellaceans of Several Small Lakes in Southwestern New Brunswick; Their Modern Distribution and Stratigraphic Importance

Abstract

Sediment-water interface samples from five small lakes in southwestern New Brunswick (Bonaparte Lake, Bocabec Lake, Gibson Lake, St. Patricks Lake and Big Pond [Deer Island]) were quantitatively examined for the presence of arcellaceans. Two major assemblages, with one assemblage (I), being subdivided into three sub-assemblages, were delineated; all assemblages were dominated by Difflugia oblonga. Reduced total and species numbers in the second, assemblage (II), of Bonaparte Lake may be a function of anoxic bottom conditions and/or acid rain pollution. Variations in most Assemblage I sub-assemblages are probably the result of chance colonization events. However, the presence of Difflugia bidens in Assemblage Ic seems to be an indicator of increased terrigenous input.

The surface information was also used to perform a first order interpretation of a core from Gibson Lake. Diversity and total numbers generally increased following transition from marine to freshwater conditions, with a decrease in total numbers in the upper part of the core, due to oxidation. Difflugia oblonga dominated all core assemblages except in the brackish freshwater transition zone, where Centropyxis aculeata dominated.

The results of this study provide further documentation of the value of arcellaceans as paleolimnoloical indicators of the benthic environment.

Keywords: Pages: 66 Supervisors: David Scott