The Environmental Protection Agency (EPA) has released a report on the condition of the nation’s lakes, ponds, and reservoirs. The National Lakes Assessment (NLA) is the first ever baseline study on the condition of the nation’s lakes.
A total of 1,028 lakes were sampled for the NLA during the summer of 2007, representing the condition of about 50,000 lakes nationwide. 56 percent of the nation’s lakes support healthy biological communities, 21 percent are in fair condition and 24 percent are in poor biological condition.
The leading stressor assessed in the NLA is poor lakeshore habitat. Lakeshore habitat is rated poor in 36 percent of lakes. Poor biological health is three times more common in lakes with poor lakeshore habitat relative to lakes with good lakeshore habitat.
The nutrients nitrogen and phosphorus rank as the next most significant stressors. About 20 percent of lakes have high levels of nutrients. Poor biological health is 2.5 times more common in lakes with high nutrient levels.
The study also measured the levels of algal toxins in lakes. A number of microbial organisms, algal toxins, and other contaminants in lakes can potentially affect human health. Microcystin – a toxin that can harm humans, pets, and wildlife – was found to be present in about one third of lakes and at levels of concern in 1percent of lakes. This could potentially have wide ranging impacts on human health and the swimability of many lakes.
A parallel study of fish tissue contaminants in the nation’s lakes shows that mercury concentrations in game fish exceed health-based limits in 49 percent of lakes, and polychlorinated biphenyls (PCBs) are found at potential levels of concern in 17 percent of lakes.
The draft National Lakes Assessment report is available for review and comment on the EPA website. The public comment period closes on Jan. 22.