Accumulation of mercury by aufwuchs in Wisconsin seepage lakes: Implications for monitoring

Abstract

We examined temporal variation in the total Hg content of aufwuchs collected from artificial substrates in 11 seepage lakes in north-central Wisconsin and its relation to the Hg content of resident yellow perch Perca flavescens from the lakes. Dry weight concentrations of Hg in aufwuchs varied temporally, as follows: summer/fall 1985 > summer 1985 > spring/summer 1986. Areal concentrations of Hg during the 1985 sampling periods were greater than concentrations during the spring/summer 1986 period, but did not differ from each other. Although chlorophyll a accrual was correlated with the areal concentration of Hg in aufwuchs during each period of study, partial correlation coefficients between Hg in aufwuchs and the chlorophyll a, organic (ash-free dry weight), and inorganic (non ash-free dry weight) content of aufwuchs during spring 1986 were not significant. Thus, we were unable to quantify the partitioning of Hg among the organic (photosynthetic, heterotrophic, and detrital) and inorganic components of the aufwuchs . Concentrations of Hg in aufwuchs were not correlated with lake pH during any of the three periods, even though the Hg content of fish in these and other lakes in the region are strongly correlated with pH. Moreover, the only significant correlation between Hg in aufwuchs and Hg in age-2 yellow perch from the lakes were weak negative correlations for areal Hg concentrations in aufwuchs during summer 1985. The analyses of aufwuchs do not indicate potential accumulation of Hg in fish in these lakes.