Regional Patterns of Total Phosphorus in Lakes of the Northeastern United States

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Abstract
A map of total phosphorus regions has been compiled for lakes in the glaciated portion of the northeastern United States. Total phosphorus data from over 2,600 of the approximately 22,000 lakes larger than 1 hectare in the study area were used for the analysis. Many of the lake regions delineated include lakes with widely differing phosphorus levels. The distinguishing feature of each region is the distribution, or mosaic, of lake phosphorus values. The pattern of values is determined by, or associated with, the particular landscape characteristics of that region and differs in comparison to patterns of lake phosphorus values in adjacent regions. Characteristics examined included: physiography, land cover/land use, vegetation (both potential and existing), soil type, and bedrock and surficial geology. For some regions, where summer lake phosphorus data were sparse, increased emphasis was placed on using combinations of landscape characteristics to refine boundaries. This method comprised using those characteristics most strongly associated with patterns of summer phosphorus data elsewhere in the region and/or patterns developed and qualitatively adjusted from lakes sampled during other seasons. Accompanying the map are descriptions of the distinctive attributes of each region, the reliability of the data used for analysis, and frequency distributions of known and estimated summer total phosphorus concentrations in lakes. The predictive power of similar regionalizations (Omernik 1987, Omernik et al. 1988) has been evaluated using independent data sets (Larsen et al. 1986, Omernik et al. 1991) and the regionalizations have proven useful for managing lakes in the Midwest (Heiskary et al. 1987, Heiskary and Walker 1988, Fulmer and Cooke 1990, Omernik et al. 1991, Lillie et al. 1993). This regionalization is offered as a framework for further verification and application to lake management decisions and the setting of regionally appropriate goals for attainable water quality in lakes of the northeastern United States.