Zebra mussels are native to lakes and waterways in Russia where a finely evolved ecosystem of predators keeps the tiny shellfish in check. The tiny mollusks are thought to have hitched a ride to North America on a freighter, arriving in the Great Lakes in 1988. From there pleasure craft spread them to other bodies of water, and they're now found throughout the eastern half of the United States as well as in California. In the absence of effective predation, the mussels' prolific reproduction has made them a significant nuisance wherever they are found.
One of the major problems caused by zebra mussels is their tendency to colonize pipes and grates, obstructing water flow through manufacturing plants, water treatment facilities and other industrial enterprises. If you live in an area that's been colonized by zebra mussels, simulate this by staking out pieces of PVC pipe under the water in several locations. Raise the pipes at intervals of several weeks or a month, and monitor the growth of mussels. Compare the mussels' growth in different environments, such as still vs. running water and rocky vs. soft bottoms.
One thing about zebra mussels that's not entirely negative is their ability to filter water. Like other bivalves, they're siphon feeders, taking in water and straining out plankton and algae for their food. In doing so, they clean the surrounding water and extract many contaminants, improving the water's quality and clarity. Demonstrate their ability to clean water by harvesting mussels from an infested waterway and introducing them into an algae-infested aquarium. Document changes in the aquarium's water quality with photos and written descriptions.
If you live in an area with a commercial freshwater fishery, a local fish plant might be willing to help you with another experiment. Ask the fish processors to save you 10 or 20 stomachs from each kind of fish they process. Dissect the stomachs and document their contents. Compare zebra mussels to other foods found in the fish stomachs, and estimate how important they are as a food source for each species.