In lake ecosystems, methylmercury–which can be toxic to people–moves up the food chain, from algae to minute, floating animals called zooplankton to fish. New experimental evidence demonstrates that the amount of methylmercury in zooplankton decreases dramatically after an algal bloom.
On the basis of computer models and field samples, some researchers have suspected that such blooms dilute toxic metals by spreading them out among the much larger number of individual algae cells–and thus offering zooplankton less-contaminated algae to feed upon.
To test this idea, graduate student Paul C. Pickhardt of Dartmouth College in Hanover, N.H. and his colleagues at Dartmouth and the University of Michigan in Ann Arbor set up 12 hot-tub-size water tanks to simulate a simple lake ecosystem. The r