Alien Species of the Week-Zebra Mussel (Economic Impacts)

Zebra Mussel (Dreissena polymorpha)

One invasive species which really caught my eye due to the rapidity of its spread and its potentially catastrophic impact on the freshwater ecosystems of North America, is the much maligned Zebra Mussel (Dreissenapolymorpha).

Zebra Mussels
(Dreissena polymorpha)

This small mollusc, averaging at around 2cm in length, is named as such because of the striped brown and yellow pattern on its shell. Native to Western Russia and the Black Sea area, they were transported to the Great Lakes region of North America via ships during the mid 1980s, with the first colonies being discovered in 1988 (Griffiths et al. 2011).

In this new environment relatively free of natural predators, its females capable of producing 100,000- 500,000 eggs per year, its population has exploded. With its ability to attach itself to hard objects (any object dropped in the water) and the long survivability of its larvae in water, it has since been able to rapidly spread to the Mississippi, its tributaries and surrounding lakes (Ricciardi et al. 2002).

Map showing the spread of the zebra mussel across the United States

The ecological impact of the mussel has been severe!! While their voracious filter feeding and breeding has greatly improved water clarity in lakes and rivers, they have also depleted the availability of microscopic organisms that play a critical part of the lake and river ecosystems. Indeed, fish numbers and biodiversity has decreased as juvenile and larval fish are starved of their main food (Maclsaac et al. 1992). Moreover, the Zebra mussels can also attach themselves to native mussels, killing them, which has resulted in the sharp decrease in native mussel numbers.

Their economic impact has been no less severe. Fisherman consistently have their lines destroyed by underwater Zebras, the future of commercial fish breeding in the Great Lakes region is at risk. They have also caused major problems for power and water treatment plants located by the lake shores – frequently clogging their water cooling intakes (Griffiths et al. 2011). 

The severity of the Zebra mussel threat to local ecosystem and their economic impact have been recognised by the Canadian and US government, as well as local government, which continue to devise plans to slow its spread.

Nevertheless, relentless conquest of North America seems unstoppable!!