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A high-resolution diatom record from Wolf Lake, a minimally disturbed 'heritage' lake, provides insights into the hydroclimatic history of the Adirondack Mountains of northern New York during the last c. 1600 years. Three pronounced dry periods occurred during c. AD 490-610, 780-870, and 1010-1080, and low precipitation generally prevailed during the warm Medieval Climate Anomaly (c. AD 950-1350), a finding that fills an important gap in knowledge of the spatial extent of droughts across North America during that period. During the cooler 'Little Ice Age' interval (c. AD 1350-1800), inferred water balance was generally more positive. Seven peaks in charcoal abundance represent fire events during both wet and dry periods. Unusually high charcoal and inorganic sediment deposition c. AD 1700 could reflect human activity in the watershed, as might an abrupt rise in the relative abundances of planktonic and tychoplanktonic diatoms in Wolf Lake during the AD 1860s. The diatom record displays periodicities of c. 256 and 512 years in addition to high-frequency fluctuations, suggesting that significant precipitation variability is likely to continue to disrupt climatic trends in this region. [ABSTRACT FROM AUTHOR]

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The relationship between 23 scaled chrysophyte taxa (Chrysophyceae and Synurophyceae) and measured limnolgoical variables in 62 Adirondack, New York, drainage lakes were examined by canonical correspondence analysis (CCA). The major proportion of variation in chrysophyte species distributions was strongly related to total monomeric Al (Al[SUBm]) and Mg concentrations, and their close correlates pH, Na, Ca, and acid-neutralizing capacity (ANC). Total monomeric Al concentrations explain a greater proportion of species variation than pH, suggesting that al[SUBm] concentrations may be more important in governing the distribution of chrysophyte laxa in these lakes. Gaussian logit (GL) and linear logit (LL) regressions of the relative percentages of individual chrysophyte taxa to lakewater pH and Al[SUBm] concentrations and the examination of pH-Al[SUBm] response surfaces show that many chrysophyte taxa exhibit unique responses to these environmental gradients; taxa can be characterized as alkaline, circumneutral, acidic, and pH indifferent. Within each of these groups, taxa can be characterized further based upon their optima and tolerances to Al[SUBm] concentrations.Chrysophyte indicator species (i.e. a taxon with a strong statistical relationship to the environmental variables of interest, a well-defined optimum, and a narrow tolerance to the variable of interest) for pH include Mallomonas hindonii, M. crassisquama, M. pseudocoronata, and Synura uvella; M. hindonii, M. crassiquama, M. pseudocoronata, S. petersenii, and S. Spinosa are good indicators of Al[SUBm] concentrations. Highly significant predictive models were developed to infer lakewater pH and Al[SUBm] concentrations from the relative percentages of chrysophyte scales in the study lakes. Model evaluation was based on th eir correlation coefficients and the root-mean-squared error of predictions (RMSE) derived from bootstrapping. Weighted averaging regression and calibration with tolerance downweighting (i.e. weighting taxa inversely to their variance) produced superior results when compared to the computationally and data-demanding maximum likelihood methods and to simple weighted average regression and calibration. [ABSTRACT FROM AUTHOR]