Invasion
Invasion Description
1st Record: East Chicago/IN/Lake George Canal, Lake Michigan (5/3/1988, Carlton 2008, several shells collected)
Geographic Extent
Duluth/MN/Duluth Harbor, Lake Superior, (1989, USGS Nonindigenous Aquatic Species Program 2008; Trebitz et al. 2012); Thunder Bay/Ontario/Lake Superior (1990, USGS Nonindigenous Aquatic Species Program 2012); East Chicago/IN/Lake George Canal, Lake Michigan (5/3/1988, Carlton 2008, several shells collected); Amoco Oil Company at Whiting/IN/Lake Michigan (1989, USGS Nonindigenous Aquatic Species Program 2008); Goderich/Ontario/Lake Huron (1990, USGS Nonindigenous Aquatic Species Program 2008); Sault Ste. Marie/Ontario/St. Marys River (1990, USGS Nonindigenous Aquatic Species Program 2008); Goderich/Ontario/Lake Huron (1990, USGS Nonindigenous Aquatic Species Program 2012)
Vectors
| Level | Vector |
|---|---|
| Probable | Ballast Water |
Regional Impacts
| Ecological Impact | Herbivory | |
| By 1992-1993, the biomass of Zebra Mussels in inner Saginaw Bay, Lake Huron, had a filtering capacity of 0.2-1.2 X the volume of the inner Bay per day. Chlorophyll and suspended solids were greatly reduced, and the decreased reflectivity (increased transparency) of the water was detectable by satellite imagery (Budd et al. 2001). Filtration by Zebra Mussels was selective- mussels ingested small, desirable flagellates, while rejecting large colonies of toxic Microcystis cyanobacteria in Lake Saginaw water (Vanderploeg et al. 2001). | ||
| Ecological Impact | Habitat Change | |
| Filtration of the water by Zebra Mussels in inner Saginaw Bay, Lake Huron, resulted in greatly increased transparency and light penetration of the water, within 2-3 years after the initial invasion (Budd et al. 2001). The introduced amphipod Echinogammarus ischnus was strongly associated with dreissenid mussels, mostly D. polymorpha (Kang et al. 2007). | ||
| Economic Impacts | Toxic | |
| The invasion of dreissenid mussels into the Great Lakes caused major changes in the foodwebs of the lakes, which also affected the passage of toxic metals and chemical through the foodweb. Mercury inputs to Lake Michigan declined, due to pollution laws enacted in the 1970s. This was reflected in dropping mercury concentrations in the flesh of Lake Trout (Salvelinus namaycush) from 1978 to the early 1990s. The Zebra-Quagga Mussel invasion led to a drop in Secchi disk depth (increased water clarity) and a decrease in the availability of high-quality pelagic prey, and an increased reliance on benthic prey. Increased light penetration and photodegradation of methylmercury leads to mass-independent fractioning of mercury isotopes, resulting in increased ratios of lighter isotopes (Delta199 Hg) in pelagic prey. As the fish relied more on dreissenid mussels and associated benthic prey (e.g. Round Goby, Neogobius melanostomus, they consumed less pelagic prey, resulting in decreases in a nitrogen isotope (delta15N) and increasing in heavy carbon isotope (lipid-corrected delta13C). This was associated a decrease in Delta199Hg ratios, and increasing ratios of heavier mercury isotopes (Delta202Hg), even as outside inputs decreased. These results suggest that the mussel invasions offset the decrease in mercury inputs by using organic mercury stored in the sediments (Lepak et al. 2019). Increased mercury in Lake Trout results in health risks to people eating the fish. | ||