Mussels play a key role in aquatic environments and are considered to be "ecosystem engineers" because they modify aquatic habitat, making it more suitable for themselves and other organisms.
One of the valuable functions performed by mussels is capturing organic matter from the water column when they siphon, processing it to build body and shell, excreting nutrients that are immediately available to plant life and then depositing the remaining organic material to the sediment making it available for other invertebrates and fish to consume. During this feeding process, the mussels "clean" the water they live in by removing phytoplankton and the bacteria and fungi that are attached to the non living organic particles they have removed from the water column. Other undesirable particles and chemicals are bound in the mussels' pseudo feces and deposited on the river bottom.
The mussel's shells provide an important substrate for algae and insect larvae to attach to. When mussels are present in large numbers, they may become underwater gardens that in turn attract fish to feed, including their host fish. Because mussels firmly anchor themselves to the lake or stream bed, they may actually stabilize the lake or stream bottom, thus minimizing the scouring affects of floods and wave action.
Mussels are also an important food source for several different kinds of terrestrial and aquatic animals, including muskrats and raccoons, as well several species of fish.
Freshwater mussels were used by early Americans. Archaeological excavations have unearthed shell material in eastern North America from sites dating back to 8000 B.C. These early people not only used the mussels for food, but also used the shells to temper pottery, and for the making of tools, utensils, and jewelry.
By the mid 1800s European Americans in the eastern United States were searching for natural pearls formed within mussel shells. Pearl hunting spread throughout the United States and "pearlers" were collecting mussels from as far west as the Mississippi River by the end of the 1800s.
Beginning in the 1890s mussel shells were harvested and manufactured into pearl buttons. These early harvesters collected mussels by the tons from the Mississippi River and its' major tributaries. Soon, the vast mussel beds in these rivers were depleted threatening this multimillion dollar industry. An effort to propagate mussels for the button factories was initiated in the early 1900's. However, pollution of the rivers doomed many of these efforts. Some mussel harvest continued until the 1940s when pearl buttons were replaced by those made from plastic.
Mussels are presently harvested for use in the cultured pearl industry. The shells are collected, ground into beads, and inserted into live oysters. The oyster's mantle secrets thin layers of mother of pearl upon the beads, resulting in a cultured pearl. These pearls are left inside the oyster from one to several years, at which time they are removed, sorted, and sold. Because many mussel species are now imperiled, many states have closed or restricted harvesting.