The Associated Press reports: More than half of the country’s rivers and streams are in poor biological health, unable to support healthy populations of aquatic insects and other creatures, according to a nationwide survey released Tuesday.

The Environmental Protection Agency sampled nearly 2,000 locations in 2008 and 2009 — from rivers as large as the Mississippi River to streams small enough for wading. The study found more than 55 percent of them in poor condition, 23 percent in fair shape, and 21 percent in good biological health.

The most widespread problem was high levels of nutrient pollution, caused by phosphorus and nitrogen washing into rivers and streams from farms, cities and sewers. High levels of phosphorus — a common ingredient in detergents and fertilizers — were found in 40 percent of rivers and streams.