Paleoecology of a wild rice (Zizania spp.) lake in Northwestern Ontario

Abstract

The high density of archaeological sites around Whitefish Lake, coupled with abundant wild rice currently growing there circumstantially indicates that this resource was economically important to precontact people. This study analyzes lake sediment cores to reconstruct the paleoecology of Whitefish Lake and document the antiquity of wild rice (Zizania spp.). A vibracorer was used to obtain a 4.5 m core from Whitefish Lake that was sampled for pollen and phytoliths at 2 cm intervals. Three additional short cores were obtained to study the modern pollen and phytolith sequence that were likely missed using the vibracorer. These cores revealed several events: 1) a deep-water phase, likely related to proglacial Lake O’Connor, followed by a Mid-Holocene arid period; and 2) the identification of wild rice microfossils dating back to roughly 6,000 cal yr BP. This research also establishes the utility of multiproxy analysis involving both pollen and phytoliths to track paleovegetation changes. The analysis also revealed the early forest that inhabited the area prior to the drying event that persisted throughout the mid-Holocene. The ped-like structures within the Whitefish Lake core, coupled with other evidence of a buried forest at the Old Fort William site (Boyd et al., 2010; Kingsmill, 2011) demonstrate the consequences of the warming and drying trends of the early to mid Holocene. Sediment and pollen profile analysis of the mid-section of the core indicate that by 4,905 cal yr BP the Whitefish Lake basin had started to fill up again with water. The subsequent bioproductivity of the lake is indicated by the sapropel in the sediment.