A Diatom-based, Paleolimnological Study of Rush Lake, Wisconsin.

Abstract

Rush Lake, located in Winnebago County, Wisconsin, is a shallow, eutrophic, lake/wetland dominated by cattails. This system has been historically important for fishing and waterfowl production. A sediment core (374 cm) was taken by employing a modified Livingstone piston corer. The core was dated was carbon-14 yielding an age date at the base of the core of 4110 +/- 40 C-14-yr. B.P. The core sediments were sampled for diatoms at 10-cm intervals, starting at 5cm (37 samples). Diatoms were counted for a total of 300 per sample. Typical of shallow lakes, the core showed signs of being extensively reworked. Sediment is often remixed due to wave action, plant roots, burrowing invertebrates, foraging carp, other bottom feeders, and periodic drying. Despite this, multivariate analysis of diatoms (PCA) suggests that this system has more eutrophic. The multivariate analysis is consistent with a pollen analysis and is likely due to human induced deforestation. There is no evidence (i.e. increase in % planktonic diatoms) that the lake had ever developed a pelagic zone for an extended period of time.