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Home , Quagga mussel, Zebra

ATMOSPH ND E A RI C C I A N D A M E I C N O I & Mussel Research S

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20 at NOAA’s N U E .S C .D R E E Years of PA M RT OM Environmental Research Laboratory MENT OF C

Zebra mussels ( polymorpha) are native to the Quagga mussels (Dreissena rostriformis bugensis) are Black, Caspian, and Azov Seas. By the early 19th century, native to the Dneiper River drainage of . Canals zebra mussels had spread to almost all major drainages built in Europe allowed range expansion of this species, of Europe because of widespread construction of canal and it now occurs in almost all Dneiper reservoirs in systems. They first appeared in Great Britain in 1824 the eastern and southern regions of Ukraine and deltas where they are now well established. Since then, zebra of the Dnieper River tributaries (Mills et al. 1996). The mussels have expanded their range into Denmark, was first sighted in the Great Lakes in Sweden, Finland, Ireland, Italy, and the rest of western September 1989, when one was found near Port Colborne, Europe. Zebra mussels were first discovered in North . After confirmation that this mussel was not America in 1988 in the Great Lakes. The first account a variety of Dreissena polymorpha, the new species was of an established population came from the Canadian named “quagga mussel” after the “quagga”, an extinct waters of Lake St. Clair, a water body connecting Lake African relative of the zebra. By 2005, quagga mussels Huron and Lake Erie. By 1990, zebra mussels had been had been found in all the Great Lakes. found in all the Great Lakes.

PHYSICAL ALTERATIONS DECLINING FISH HEALTH DIPOREIA DECLINES The hydraulic flow regime of the Detroit While many species of fish will readily Diporeia, a tiny shrimp-like organism, River has changed since the arrival of eat Diporeia (see right), few species can was the dominant benthic invertebrate zebra mussels in the late 1980’s. Although use zebra and quagga mussels efficiently in most offshore areas of the Great Lakes the amount of change is difficult to quan- for food. Moreover, even if a fish since the glaciers receded ~10,000 years tify, GLERL analyses shows roughness species does eat these mussels, the loss ago. Diporeia have a high lipid (fat) and slope differences in the lower reach of Diporeia has left many of them with content, with lipids often exceeding 30% resulting in a change in the hydraulic re- food choices much lower in nutrition of its total weight. As a result, it is rich gime after 1988. than Diporeia. In Lake Erie, a severe in calories and a good source of energy decrease in smelt stocks was seen in the for fish. Since the early 1990s population 1990s. Estimates of the slimy sculpin and densities of Diporeia in all the lower Great lake trout populations in Lake Ontario Lakes have dropped dramatically. “Exact showed a 95% decline between the late mechanisms are unclear, but the decline 1980s and 1996. In , many of Diporeia is related to the introduction fish populations are now sacrificing and expansion of the zebra and quagga health to feed off zebra mussels. mussels,” says Tom Nalepa, a GLERL Whitefish, for example, shifted from a biologist who has been sampling Lake diet of 25-75% Diporeia to a diet of zebra Michigan sediments since the early 1980s. mussels. During their first 2 weeks of life, larval bluegill reared in the presence of mussels grew 24% slower than fish reared alone. Alewife energy density was “reefs” have dramatically 23% lower during 2002-2004 (post zebra altered the bottom contours of some mussel invasion) compared to 1979-1981 lakes and rivers. (pre zebra mussel invasion). As a result, a Chinook salmon now needs to eat 22% more alewives to attain an ideal body Diporeia weight by age 4. Zebra Mussel Distribution Quagga Mussel Distribution

1994/95 2000 2005 1994/95 2000 2005

101 102 103 104 105 101 102 103 104 105

Density (No. per m2) Density (No. per m2)

NATIVE MUSSELS BENTHIC HARMFUL ALGAL BLOOMS LIMINATED PROMOTED Nuisance blooms of the toxic blue-green E alga Microcystis have returned to many Zebra mussels attach to the shells of na- Zebra mussels altered inner Saginaw portions of the Great Lakes since 1992. tive mussels and alter normal life-sustain- Bay from a pelagic-dominated system These recent blooms started a few years ing activities such as feeding, breathing, to a benthic/pelagic system, which will after the invasion of zebra mussels and and eliminating waste products. In addi- have long-term effects on food web their cousins the quagga mussels in the tion, large populations of zebra mussels structure and productivity at higher Great Lakes. substantially reduce the amount of food trophic levels. They are very effective available to the native mussels. NOAA’s filter feeders. Because of their population Using special video equipment, Great Lakes Environmental Research densities, zebra mussels remove much NOAA’s Great Lakes Environmental Laboratory (GLERL) has monitored of the particulate matter from the water Research Laboratory (GLERL) showed populations of native mussels in Lake St. column, leaving the water very clear and that mussels reject Microcystis but eat Clair periodically since 1986. Based on allowing increased light penetration. other algae. Thus, the competitors of surveys between 1986 and 1997, it can This produced a significant increase in Microcystis are removed. At the same be stated that native mussels have been productivity of bottom plants and the time, the mussels completely elimi- amount of bottom area covered with are excreting nated from the plants. nutrients open waters (phosphate of Lake and ammonia) St. Clair. derived from the they eat. These nutrients, in turn, serve to fertilize further growth of ALTERED CONTAMINANT Microcystis. CYCLING Algae growth causes muck Zebra and Quagga mussels have the po- accumulation along the shoreline. tential to change contaminant cycling in the Great Lakes by rerouting dissolved For more information: Selected Publications List from and particulate-bound contaminants NOAA, Great Lakes into mussel food chains, with possible 20 Years of GLERL Environmental Research Laboratory biomagnifications in mussel predators Dreissenid Research 4840 S. State Rd. and transfer into upper trophic levels. Ann Arbor, MI 48108, 734-741-2235 Selective predation on small, pre-spawn- www.glerl.noaa.gov/pubs/ ing (high lipid) mussels may present a brochures/20dreissenidrefs.pdf greater hazard than predation on larger www.glerl.noaa.gov mussels. May 2008