Invasion
Invasion Description
1st Records: Straits of Mackinac/MI/Lake Michigan (found at 6 of 37 sites sampled) (1997, Nalepa et al. 2001); off Alpena/MI/Lake Huron (1997, USGS Nonindigenous Aquatic Species Programs 2008); ~4 mi W of St. Ignace/MI/Lake Michigan (1997, USGS Nonindigenous Aquatic Species Program 2008); near Charles/MI/St. Martin Bay, Lake Huron (1997, USGS Nonindigenous Aquatic Species Program 2008)
Geographic Extent
Straits of Mackinac/MI/Lake Michigan (found at 6 of 37 sites sampled (1997, Nalepa et al. 2001); off Alpena/MI/Lake Huron (1997, USGS Nonindigenous Aquatic Species Program 2008); ~4 mi W of St. Ignace/MI/Lake Michigan (1997, USGS Nonindigenous Aquatic Species Program 2008); near Charles/MI/St. Martin Bay, Lake Huron, St. Martin Bay (1997, USGS Nonindigenous Aquatic Species Program 2008); Gull Island Reef/MI/Lake Michigan (2000, Nonindigenous Aquatic Species Program 2008); Muskegon/MI/Lake Michigan (2001, USGS Nonindigenous Aquatic Species Program 2008); off North Chicago/Lake Michigan (2003, USGS Nonindigenous Aquatic Species Program 2008); Superior/WI/Lake Superior in Duluth-Superior Harbor (2005, Grigorevich et al. 2008; USGS Nonindigenous Aquatic Species Programs 2008; Trebitz et al. 2012)
Vectors
| Level | Vector |
|---|---|
| Alternate | Ballast Water |
| Alternate | Hull Fouling |
Regional Impacts
| Ecological Impact | Competition | |
| By 2008, D. bugensis was the overwhelming dominant at a sampling site at 45 m depth, off Muskegon, MI (Vanderploeg et al. 2010), where D. polymorpha was the sole dreissenid in 1999 (Nalepa et al. 2001). Quagga Mussels developed populations in deeper waters around reefs offshore of Milwaukee, WI, in Lake Michigan, and kept filtering through the winter at low temperatures. This filtering lowered phytoplankton concentration in spring, when Zebra Mussels, which are dormant in winter, begin to start feeding again. The difference in the seasonality of feeding led to the complete replacement of Zebra Mussels by Quagga Mussels on offshore reefs (Cuhel and Aguilar 2013). | ||
| Ecological Impact | Herbivory | |
| Grazing experiments with the 'profunda' morph of D. bugensis (from the 45m site off Musekegon, MI) indicated that the filtering capacity of the mussel biomass in the 30-50 m zone exceeded the growth rate of the phytoplankton by several times, resulting in a disappearance of the spring bloom, and a nutrient sink, which decreased the resources available in deeper offshore waters (Vanderploeg et al. 2010; Evans et al. 2011). | ||
| Ecological Impact | Trophic Cascade | |
| Reduction of the phytoplankton sinking to the deeper parts of the lake bottom, as a result of Dreissena grazing, is a possible factor in the decline of the benthic amphipod Diporeia, a dominant deposit-feeder, and an important food for many great lakes fishes, including the commercially important Lake Whitefish (Coregonus clupeiformis) and Bloater (C. hoyi) (Vanderploeg et al. 2002; Cuhel and Aguilar 2013). Because of the year-round decrease in phytoplankton biomass, the biomass of zooplankton is expected to decrease, in turn decreasing the abundance of forage fishes (Cuhel and Aguilar 2013). Grazing by D. bugensis through the winter and early spring has eliminated the spring diatom bloom, and altered nutrient cycles, so that a spring decrease in silica (a nutrient required by diatoms) no longer occurs. The planktonic foodweb in Lakes Michigan and Huron now resemble that of the more oligotrophic Lake Superior (Evans et al. 2011). Quagga Mussels (Dreissena bugensis ) now domijnate phoisphoirus cycling in the lower Great Lakes.. 'The tissues and shells of quagga mussels now contain nearly as much phosphorus as the entire water columns of the impacted Great Lakes' (Li et al. 2021) | ||
| Ecological Impact | Habitat Change | |
| Heavy settlement of Quagga Mussels around offshore reefs in Lake Michigan, led to increased structure and sedimentation on rocky surfaces, and limited scouring of sediments. On level, soft silt/clay sediments, dense colonies of mussels created new, complex structure. The large filtering biomass led to increased water clarity, and increased depth of algal growth, dimnishing spawning habitat for Lake Trout (Salvelinus namaycus), which prefer to spawn in darkness, on bare cobble bottoms. Condition index of Lake Whitefish decreasesd, but began to recover, as fish started to feed on mussels (Cuhel and Aguilar 2013). | ||
| Ecological Impact | Food/Prey | |
| The Lake Whitefish (Coregonus clupeaformis) appears to be in the process of incorporating dreissenid mussels into its diet. Whitefish in Lake Huron consume mussels at a rate 8X higher than those in Lake Michigan, which may be contributing to a higher whitefish biomass (2X) in Lake Huron (Madenjian et al. 2010). | ||
| Economic Impact | 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 (Delta 199 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 (delta 15N) and increasing in heavy carbon isotope (lipid-corrected delta 13C). This was associated a decrease in Delta 199Hg 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. | ||