the interesting  local case of the zebra mussel
Invasion History
 
- zebra mussels (fig.1) Dreisenna polymorpha are not native to North America  but to the Caspian Sea, Black Sea, and Azov Seas of Asia.
- the mussels then spread throughout Europe in canals that were built in the 18th century.
- by the 1830s, mussels inhabited much of Europe and  Britain.
 
- zebra mussels are believed to have entered U.S. waters when ballast (used to stabilize empty cargo ships on the ocean)  from a transoceanic vessel was discharged into Lake St. Clair, near Detroit, Michigan, where they were discovered in 1986-88. Since the, zebra mussels have spread to all of the Great Lakes and many inland waterways in several states, along with Ontario and Quebec, Canada.
- billions of zebra mussels have reproduced and are now hard to control.
                                         Life History  
                                        view slide show of life history

- mollusks/gastropods/bivalves Dreisenna polymorpha
- filter feed ambient waters for zoo/phytoplankton and suspended detritus
- attach to substrate (rocks, pipes, boats, clams anything solid) using byssal threads
- live in high density groups of many age classes

- age of first reproduction is very young thousands of eggs produced per year throughout summer
- eggs and sperm meet in open water have high likelihoods of fertilization
- offspring are planktonic (veliger larvae) and thus dispersal is enhanced
- only a few predators eat Zebra mussels and none exclusively
- boaters and fisherman accidentally vector the adults on boats / veligers in bait buckets

Effects on the ecosystem

- zebra mussels compete for substrate with other native mussels and invertebrate populations
- zoo/phytoplankton base of aquatic food chain is disrupted
- water column becomes less turbid allowing deeper penetration of light which encourages weed growth in many areas where this was not normal
- water pollutants are concentrated in feces, feces also harbor the Botulinium toxin which has recently killed loons on Long Point Lake Erie
- boats are fouled , water intake pipes for civic/industrial applications are congesting

- they are here to stay, their populations have imparted both good and bad qualities to the ecosystem

- hardyness, rapid maturity, high fecundity, wide dispersal in larvae stage (veliger) and ability to adapt to new environments have given the Zebra Mussel a high degree of fitness and success as a species