[Watersheds] Release of the National Lakes Assessment 2012 Report

[Panciera, Ernie (DEM)]

As received from EPA:

From: Lehmann, Sarah [mailto:Lehmann.Sarah at epa.gov]
Sent: Thursday, December 08, 2016 11:22 AM
Subject: Release of the National Lakes Assessment 2012 Report

Hello NARS partners (apologies for cross-postings):

We are pleased to announce that the National Lakes Assessment 2012 Report was released today, December 8th.  This report is the culmination of a significant partnership between EPA, states, tribes, and other partners. The NLA report and underlying data are posted at http://www.epa.gov/national-aquatic-resource-surveys/nla.  Additional information from the NLA, including assessment of conditions at regional scales, differences between natural lakes and reservoirs, and an opportunity to explore population-level results in an interactive dashboard are also available on the NLA website.  The interactive dashboard can be accessed directly at https://nationallakesassessment.epa.gov/.

A few key findings from the report include the following:



-          The NLA indicates that nutrient pollution is common in U.S. lakes; 40% of lakes have excessive levels of total phosphorus and 35% have excessive levels of total nitrogen. Nutrient pollution is the most widespread stressor among those measured in the NLA and can contribute to algae blooms and affect public health and recreational opportunities in lakes.

-          We find that 31% of lakes have degraded benthic macroinvertebrate communities, while 21% of lakes have degraded zooplankton communities. NLA exploratory analyses indicate an association between nutrients and biological condition, with lakes with phosphorus pollution likely also to have a degraded biological condition.

-          A comparison of the 2007 and 2012 National Lakes Assessments indicates little change between surveys. In most cases, the percentage of lakes in degraded biological, chemical and physical condition did not change at the national scale over this five-year period.

o   One notable exception to this pattern was observed with algal toxin measures. An analysis of cyanobacteria cell density, a measure of the density of cells that could produce cyanotoxins, shows a statistically significant increase (+8.3%) in the percentage of lakes in the most disturbed category between 2007 and 2012. The NLA identified a significant increase in the detection of microcystin among lakes in 2012 (+9.5%). However, concentrations of this algal toxin remained low and rarely exceeded WHO recreational levels of concern (<1% of the population) in both assessments.

o   Another difference emerged through additional in-depth analyses of nutrient data. While we did not observe changes in the condition categories, analysts found a dramatic 18.2% decline in the percentage of oligotrophic lakes (<10 μg/L of total phosphorus) and an overall increase in the median concentration of phosphorus across all lakes.

We rely heavily on the contributions and expertise of all of you to complete the surveys and each of the reports. Thank you for all of your contributions to the NLA by participating in survey planning, conducting sampling and lab analysis, reviewing data and the report.  We are very appreciative of your time, effort, and expertise.

If you have any questions, please contact Amina Pollard, the NLA Lead, (pollard.amina at epa.gov<mailto:pollard.amina at epa.gov>) or me.

Sincerely,
Sarah

Sarah Lehmann
202-566-1379
Lehmann.sarah at epa.gov<mailto:Lehmann.sarah at epa.gov>

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