agricultural runoff

Serious algae outbreaks have hit more than 20 states this summer. Algae blooms aren't unusual. But the frequency, size and toxicity now are worse than ever, and changes in climate are partly to blame.

Across the Midwest this summer, scientists are wading into 100 streams to collect water samples and check cages for fish eggs. It's part of a large study to understand how pesticides and agricultural chemicals from farms are affecting the nation's streams.