Loosestrife & Mussels

Aliens invading our space:

Ever feel a little crowded, like there wasn’t room for you? Now you know how some of our local animals and plants feel. Two very local threats to biodiversity are the invasive species of zebra mussels and purple loosestrife. Zebra mussels (Dreissena polymorpha) are small striped bi-valves that are infesting the waters of the Great Lakes region. Purple Loosestrife (Lythrum salicaria) is a beautiful purple-flowered plant that is crowding out other plants in our local wetlands (USDA 2000). These are just two non-native species that are killing off our resident animals and plants.

The Trouble with Tribbles...and Mussels...and Loosestrife:

These invaders are contributing to a decline in biodiversity in our region. Zebra mussels contribute to the die off of other species in a number of ways. The mussels eat up phytoplankton needed by other species. Their water filtration activity clarifies water, which affects the habitat of native species of other flora and fauna. Also, they attach themselves to other species of crustaceans, which impedes their growth and movement. The populations of waterfowl are affected, also. Some populations increase because the mussels are an abundant source of food for some waterfowl. Others decrease because their usual sources of food were killed off by the presence of the zebra mussels (Yount 1990).

Purple loosestrife simply takes over. Because it can produce up to 21,000 seeds/m2, it spreads throughout a habitat very quickly. Once it begins to spread, it crowds out other species of plants. Then, because it is unpalatable to wildlife, species of animals decline because native food sources have been eliminated (Reznicek 1990). “An estimated 190,000 hectares of wetlands, marshes, pastures and riparian meadows are affected in North America each year, with an economic impact of millions of dollars” (Minnesota Sea Grant 2000).

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