Whittier, T., S.G. Paulsen, D. P. Larsen, S.A. Peterson, A. Herlihy, and P. Kaufmann. 2002. Indicators of ecological stress and their extent in the population of Northeastern Lakes: A regional scale assessment. Bioscience 52(3):235-247 WED-01-067
One of the Environmental Monitoring and Assessment Programís first projects was a survey of 345 lakes in the eight states of the Northeast, during summers of 1991-1996. This survey was the first regional-scale attempt to use a probability-based sampling design to collect biological assemblage data along with a broad range of physical and chemical indicators of stress to lake ecosystems. This paper applies these data to five issues of concern for lake ecosystems: nutrient enrichment, acidification, metals contaminants in fish tissue, non-native invasions, and riparian disturbance. It focuses on estimates of the extent to which the population of lakes in the Northeast were in impaired condition or subject to ongoing stress. These estimates of extent provide some of the previously unavailable data needed to develop relative rankings of stresses to Northeast lakes.
Nearly half (47%) of the northeastern lakes were human-made impoundments; most of these were in the lowland ecoregions. Sediment diatom data indicate that natural lakes in the Northeast were rarely eutrophic in the past. In the 1990s, an estimated 24% of lakes and impoundments were eutrophic or hypereutrophic and were considered to be degraded; 83% of these were impoundments. Fish in 24% of lakes had mercury concentrations exceeding 0.2 µg/g, a commonly used "action level" above which States may issue advisories against eating fish. Fish assemblages in northeastern lakes were extensively stressed by non-native species. Only 21% of lakes had no non-native fish, while 15% of lakes had more non-native species than natives. Shoreline alteration was fairly extensive, with 23% of lakes having visible evidence of human activity at half or more of the riparian assessment stations. Acidification was the least extensive stress in the region, with 2% of lakes being acidic and another 12% being acid-sensitive.