Download
1 / 31
340 likes | 1.21k Vues
Zebra Mussels What are Zebra Mussels? Scientific Name: Dreissena polymorpha Zebra mussels are small shellfish (as small as a kidney bean) Although variable, most have a striped shell pattern Multiple color patterns Some of the zebra mussels have no stripes Name Origin
E N D
What are Zebra Mussels? • Scientific Name: Dreissenapolymorpha • Zebra mussels are small shellfish (as small as a kidney bean) • Although variable, most have a striped shell pattern • Multiple color patterns • Some of the zebra mussels have no stripes
Name Origin • The species name of the zebra mussel scientific name polymorpha means “many forms,” like their color varieties • Zebra mussels are members of the phylum Mollusca (mol-US-ka), or mollusks • Mollusca is from the Latin word mollis, which means soft • All slugs, snails, octopi, clams, and oysters are mollusks • Mussels are bivalve mollusks • Bivalves have two shells that are held together by a strong ligament
How quickly do they multiply? Each Zebra mussel is able to produce from thirty thousand to one million eggs each year All fertilized eggs develop quickly into free-swimming larvae called veligers Veligers are smaller than the period at the end of this sentence. Veligers feed on tiny phytoplankton (such as algae or small freshwater plants), and by drifting with water currents they can travel great distances Wikipedia image of some different types of phytoplankton
Veliger larvae of the Zebra Mussel photographed using two different light sources.
After three to four weeks, they must find something to attach to or die • Once they have attached themselves, the veligers change from free-swimming larvae to anchored mussels • However, 95% of veliger larvae do not survive this stage • Young zebra mussels reach their sexual maturity during their first year • Zebra mussels attached to a flow meter in Lake Michigan
Predators • Zebra mussels have high nutritional value, and are consumed in large quantities by crayfish, waterfowl and muskrats • Nutritional value changes seasonally, varying in protein and carbonate content • Crayfish can have a significant impact on the densities of 1 to 5 mm long zebra mussels. An adult crayfish consumes an average of nearly 105 zebra mussels everyday, or in all about 6000 mussels in a season. Predation rates are significantly reduced at cooler water temperatures. • Also, fishes of the carp and minnow Family (Cyprinidae) are known to consume zebra mussels
Where did zebra mussels originate? • Zebra mussels originally came from the Black, Caspian and Aral Seas • By the late 18th and early 19th centuries, zebra mussels spread to most of the major drainages of Europe • This was due to the widespread construction of the canal system • Zebra mussels were able to spread to Great Britain by the 1830s
Dispersal • Adult Zebra mussels travel on boats, attached to the hull or other surface • Larvae can travel in the ballast water of ships When a ship travels out into the open ocean, it needs to carry extra weight (ballast) in order to maintain an even keel (stability). Nowadays the most common form of ballast is water. The water that is used for the ballast (along with anything that is in it) is picked up in the homeport, carried with the ship, and then is dumped out as they prepare to load cargo • So, wherever the ship goes, so does whatever else that is on it. An entire field of study, ballast ecology, developed during the 1990’s.
Arrival in America • Jonathan Bossenbroek, an ecologist at the University of Toledo, believes that the zebra mussel initially entered the United States in 1988 • This was most likely through the ballast water from international cargo ships traversing the St. Lawrence Seaway • Another possible mode of introduction is on anchors and chains, although this has not been proven • Zebra mussels were first noticed in Lake Erie and Lake St. Clair; since then they have spread throughout much of the Eastern United States and Canada
Lake St. Clair and Lake Erie were the first recognized North American locations of the zebra mussel
Where are they spreading? • Since their release into Lake St. Clair and Lake Erie, zebra mussels have been found in all five Great Lakes • They have even been spotted in the St. Lawrence River, the Finger Lakes region of New York, and the Mississippi River basin • Many Division of Natural Resources officials are worried that the zebra mussels will make it up to Maine, since Vermont has been effected • Zebra mussels are even pushing out west, having been found in Lake Powell and the Colorado River
Map of the zebra mussel sightings throughout the United States up to April 2005. However, there are now sightings of zebra mussels in California, Colorado, Kansas, Oklahoma, and parts of Iowa (the following site has an updated map) http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/zebramusseldistribution.asp
How can they move so quickly? • Cargo shipping via the world’s waterways has increased greatly in the past 50 years thus increasing the chance for introductions via ballast water. • Adult zebra mussels readily attach themselves to boats and can survive out of water by simply closing their shells tightly • Since boats do not stay in one place, the zebra mussels that attach become mobile
Slow the spread • In order to avoid spreading zebra mussels to new areas, agencies advise you to keep your boat clean • The general recommendation is to keep the vessel out of water and dry for a minimum of 30 days after cleaning all equipment and draining all possible sources of standing water • Quarantine times may be reduced due to local temperatures or relative humidities
Zebra mussels can survive for a long time out of water In fact, adult zebra mussels can survive out of water for several days or weeks if the temperature is low and humidity is high Recommended quarantine times when drying out a boat: January - 51 Days February - 32 Days March - 21 Days April - 13 Days May - 8 Days June - 5 Days July - 5 Days August - 5 Days September - 5 Days October - 13 Days November - 21 Days December - 51 Days
How are zebra mussels harming the marine life? • Zebra mussels have been known to affect the natural ecosystems both directly and indirectly • One of their most noticeable impacts is their feeding behavior • Since zebra mussels are filter feeders, they take up everything in the water, about one gallon per day per mussel • All particles within the water column of any infected area are removed or eaten by the mussels • Non-digestible items are wrapped in mucus and spit out, falling to the ocean floor • Whenever high densities occur, zebra mussels are capable rapidly clearing the water
When lakes clear up, the light level increases, causing the aquatic plants to increase in both number and size • This increase could be beneficial to some fish such as the northern pike and yellow perch • However, this can cause problems for recreational boaters and swimmers • There is also a possibility of increasing taste and odor problems with drinking water supplies, as zebra mussels can block water-intake pipes during a heavy rain event
What other harmful affects do zebra mussels have?- remember, “Everything is connected to everything else” • Benthic macroinvertebrates (tiny invertebrates such as Diporeia) play a major role in the food chain and by cycling materials • However, changes are occurring within the food web due to zebra mussels, including major changing within benthic macroinvertebrate populations • Many fish species, like whitefish, feed on Diporeia, and when their numbers decline so do their predators Diporeia
One of the more drastic impacts of zebra mussels are their influence in causing the near extinction of native American unionid clams in Lake St. Clair • Also found to be the case for the western basin of Lake Erie • Zebra mussels will attach and build colonies on native species of clams, hindering movement and overall fitness Zebra mussels attached to a native clam found within the Great Lakes region
Interesting Zebra Mussel attachments • Sometimes they even attach to one another • Zebra mussels tend to colonize on just about anything, including native clams, boats, plants, and slow moving animals • Zebra mussels have also been known to attach to trash that can be found in water bodies Terrible waste of a good beer can Zebra mussels attached to a crayfish (top) and a snapping turtle (bottom)
Since zebra mussels attach to water intakes, surrounding areas could go for days without any water • Companies that use water to power their plants can have trouble keeping them up and running • A number of plants in the Great Lakes regions are having trouble keeping the zebra mussels out of their water intake pipes Zebra mussels encrusted inside water pipes
The 100th Meridian Initiative represents the first comprehensive and strategically focused effort This effort is in cooperation with federal, state, tribal and provincial agencies that address potential pathways to prevent the westward spread of the zebra mussels Also works to stop other aquatic nuisance species Some of the goals of the 100th Meridian Initiative include: Preventing the spread of zebra mussels and other alien species in the 100th meridian jurisdictions and westward Monitoring and controling zebra mussels and other alien species if detected in these areas Goals can be achieved by: Information and education Voluntary boat inspections Monitoring Rapid response
This map shows the dividing line for the 100th meridian; the right side is where most of the zebra mussel populations are found, and the left side where populations are starting to appear
Why the big concern? • If the zebra mussels do get past the dividing line, major problems can start in water systems throughout the west • It could devastate water resource projects, raw water users, and also harm aquatic ecosystems • When zebra mussels infest the headwater reservoirs, they are more than likely to inhabit and colonize thousands of canals used to transport water to millions of people • Since water is very important for agriculture, the 100th meridian is worried that zebra mussels will get into the water system used for crops
Word of mouth is crucial to educating the public Information is being disseminated through numerous ways including print, electronic sources, news coverage, billboards, etc. As boaters move closer to the dividing line, information about the zebra mussels is more intense Trained personnel are stationed along 11 major highways to conduct voluntary boat inspections and boater surveys The 11 major highways are: US2 I-40 I-94 I-20 US12 I-10 I-90 I-44 I-80 I-70 US54 Ways to Control the Problem
Boat inspections are taking place at weigh stations, highway rest areas/welcome centers, restaurants and service/motel complexes on interchanges Most inspections target boats and trailers Effective monitoring is important to ensure that zebra mussels are detected before they reach open waters Early detection of zebra mussels can decrease their potential impact on native resources, man-made structures, and the economy Waterways west of the 100th meridian will be assessed by federal and state agencies to determine their potential for zebra mussel infestation
One of many signs along the 100th meridian emphasizing to boaters the potential spread of exotic species. These are up at boating docks and rest stops along highways Boat inspections take place in many locations, due to the zebra mussel being able to cling to multiple surfaces
The Cost of Control- a series of examples • For example, by 2001, Wisconsin Electric Power Company reported that they were spending $1.2 million per year in control efforts • In 2003, 12 North American nuclear plants infested with mussels spent on average $825,000 per year each for control • In Canada, Ontario Hydro has reported zebra mussel impacts of $376,000 annually per generating station (1994) • The estimated annual cost of controlling zebra mussels in the Great Lakes is from $100 to $400 million dollars (2004) • The U.S. Fish and Wildlife Service estimates the potential economic impact to be at least five billion dollars over the next ten years to U.S. and Canadian water users within the Great Lakes region alone (2003)
