A Survey of the Nation’s Lakes – EPA’s National Lake Assessment and Survey of Vermont Lakes Vermont Agency of Natural Resources Department of Environmental Conservation - Water Quality Division 103 South Main 10N Waterbury VT 05671-0408 www.vtwaterquality.org Prepared by Julia Larouche, Environmental Technician II January 2009 Table of Contents List of Tables and Figures........................................................................................................................................................................... ii Introduction................................................................................................................................................................................................. 1 What We Measured..................................................................................................................................................................................... 4 Water Quality and Trophic Status Indicators.......................................................................................................................................... 4 Acidification Indicator............................................................................................................................................................................ 4 Ecological Integrity Indicators................................................................................................................................................................ 4 Nearshore Habitat Indicators .................................................................................................................................................................. 5 Recreational Integrity Indicators............................................................................................................................................................. 5 What We Found .......................................................................................................................................................................................... 7 Trophic Status Indicators ........................................................................................................................................................................ 7 Chlorophyll-a ...................................................................................................................................................................................... 7 Secchi Disk Transparency................................................................................................................................................................... 9 Total Phosphorus .............................................................................................................................................................................. 10 Total Nitrogen................................................................................................................................................................................... 11 Dissolved Oxygen............................................................................................................................................................................. 12 Acidification Potential assessed using Alkalinity............................................................................................................................. 14 Ecological Indicators ............................................................................................................................................................................ 16 Littoral Habitat.................................................................................................................................................................................. 16 Aquatic Macrophytes and Aquatic Invasive Species (AIS).............................................................................................................. 18 Woody Habitat.................................................................................................................................................................................. 20 Comparison to National Data.................................................................................................................................................................... 21 What It All Means..................................................................................................................................................................................... 21 References................................................................................................................................................................................................. 25 A Survey of the Nation’s Lakes – Vermont Lakes i List of Tables and Figures Table 1. Vermont lakes (n=52) included in the National Lake Survey. *Asterisk indicates Core NLA lakes.......................................... 3 Table 2. Description of trophic states for Vermont lakes (taken from the Vermont Volunteer Surface Water Monitoring Guide). ........ 5 Table 3. List of 2008 Survey Lakes that are affected by four particular aquatic invasive species (Eurasian watermilfoil, water chestnut, purple loosestrife, and curly-leaf pondweed). For Eurasian watermilfoil and water chestnut, letters indicate the density of the plant population (L=light, M=moderate, H=heavy, C=controlled). .......................................................................................... 19 Figure 1. Distribution of lakes nationwide included in the survey (www.epa.gov). ................................................................................. 1 Figure 2. Distribution of Vermont lakes from the random selection provided by the National Lake Survey........................................... 2 Figure 3. Chlorophyll-a values observed in Vermont Survey Lakes during the 2007/2008 summer sampling campaign with corresponding trophic state ranges. Pie chart shows the percent of VT Survey lakes that fall into each range. Margin of error is +/- 5%....................................................................................................................................................................................... 8 Figure 4. Bar graph of Secchi transparency measurements observed in Vermont Survey Lakes during the 2007/2008 summer sampling campaign with corresponding trophic state index ranges. Pie chart shows the percent of VT Survey lakes that fall into each range. Margin of error is +/- 5%. ................................................................................................................................9 Figure 5. Total phosphorus values observed in Vermont Survey Lakes during the 2007/2008 summer sampling campaign with corresponding trophic state index ranges. Pie chart shows the percent of VT Survey lakes that fall into each range. Margin of error is +/- 5%........................................................................................................................................................................ 10 Figure 6. Total nitrogen values observed in Vermont Survey Lakes during the 2007/2008 summer sampling campaign..................... 11 Figure 7. DO and temperature profiles for oligotrophic and eutrophic lakes throughout the seasons. Lake depth is typically on the vertical axis and temperature and DO are on the horizontal axes. Please see this website for the source of this schematic and a detailed description of dissolved oxygen dynamics in lakes throughout the year. ................................................................. 12 Figure 8. Dissolved oxygen: percent of water column that is less than 5 mg/liter for Vermont Survey Lakes during the 2007/2008 summer sampling campaign. Lakes were identified as fair when >50% of the water column was < 5 mg/l. Accounting for natural attributes, no lakes were considered impaired............................................................................................................... 13 Figure 9. Alkalinity values observed in Vermont Survey Lakes during the 2007/2008 summer sampling campaign. Pie chart shows the percent of VT Survey lakes that fall into each range. Margin of error is +/- 5%. Note the acid-sensitive Little Rock Pond has a high weight, implying a higher percentage of acid stressed lakes than have been documented by Vermont’s long-term sampling programs. Omitting this datapoint, the percentages are: impaired, 3%; stressed, 12%; attaining, 85%................... 15 Figure 10. Percentage of shoreline development in Vermont Survey Lakes during the 2007/2008 summer sampling campaign. Pie chart shows the percent of VT Survey lakes that fall into each range. Margin of error is +/- 5%. .......................................... 17 Figure 11. Percentage of total macrophyte cover in Vermont Survey Lakes during the 2007/2008 summer sampling campaign. Pie chart shows the percent of VT Survey lakes that fall into each range (Low, Medium and High Structural Habitat). Margin of error is +/- 5%............................................................................................................................................................................ 18 A Survey of the Nation’s Lakes – Vermont Lakes ii Figure 12. Percentage of 2008 Vermont Survey Lakes that are affected by AIS including Eurasian watermilfoil (Myriophyllum spicatum), curly-leaf pondweed (Potamogeton crispus), water chestnut