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REGIONAL LAKE TROPHIC PATTERNS IN THE NORTHEASTERN UNITED STATES: THREE APPROACHES
Citation:
Peterson, S., D. Larsen, S. Paulsen, AND N. S. Urquhart. REGIONAL LAKE TROPHIC PATTERNS IN THE NORTHEASTERN UNITED STATES: THREE APPROACHES. Environmental Management 22(5):789-801, (1997).
Description:
During the summers of 1991-1994, the Environmental Monitoring and Assessment Progam (EMAP) conducted variable probability sampling on 344 lakes throughout the northeastern United States. Trophic state data were analyzed for the Northeast as a whole and for each of its three major ecoregions-the Adirondacks (ADI), the New England Uplands (NEU), and the Coastal Lowland and Plateau (CLP)-and inferred to the entire population of lakes 1 ha(N=11,076). Results were compared to a large, nonrandomly sampled data set for the same area complied by Rohm and others and contrasted with lake trophic state information published in the National Water Quality Inventory: 1944 Report to Congress [305(b) report. Lakes across the entire Northeast were identified by EMAP data as 37.9%( 8.4%) oligotrophic, 40.1%( 9.7%) mestotrophic, 12.6%( 7.9%) eutrophic, and 9.3%( 6.3%) hypereutrophic. Lakes in the AD1 and NEU generally are at a low, nearly identical trophic state(96% oligotrophic/mesotrophic), while those in the CLP are much richer (45% eutrophic). EMAP results are similar to results of the Rohm data set across the entrie region. In the CLP, however, EMAP identified approximately 45% of the lakes as eutrophic/hypereutrophic, while the Rohm data set identified only 21% in these categories. Across the entire Northeast, the 305(b) report identified a much higher proportion (32.2%) of lakes in eutrophic condition and a much smaller proportion (19.8%) in oligotrophic condition than did the EMAP survey data(12.5% 7.9% and 37.9% 8.5%, respectively). Probability sampling has several advantages over nonrandom sampling when regional resource condition assessment is the goal.