This is how the zebra mussel was first brought into North America. Each mussel is roughly two inches long and lives for a period of five years. The zebra mussel was first detected in the United States in 1988, but probably reached the US in 1986 on board a freighter as mentioned above, based on how large the colonies had become when detected. Female zebra mussels lay approximately 30,000 eggs per year which then become microscopic, floating larvae. Zebra mussels provide several benefits to the waters in which they live.
Mussels can also filter out green-brown algaes, which frequently discolor water.
However, there seem to be many, more negative aspects of the zebra mussel. Zebra mussels outgrow native clam and mussel species by ten to twenty times and attach themselves to other mollusks' shells which then cannot open to feed, in effect strangling them. The largest problems involve where the mussels attach themselves for their five year lives. Zebra mussels have submerged navigational bouys because of the weight of their colonies. More significantly, the mussels pose a serious economic cost to many industries in the Great Lakes area.