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Zebra Mussel Invasion of the Hudson River Name ______________________________

Background: Period _____ Date ___________________

Large ships that move cargo to and from various ports around the world, often times can be carrying more than just the intended cargo.

For example, Zebra Mussels, native to Eastern Europe and Western Asia, were first discovered in the lower Great Lakes in 1988. It is likely they were introduced to the United States through ballast water in large ships.

Zebra Mussels (Dreissena polymorpha)

Over the next dozen years, they spread rapidly throughout parts of the eastern U.S. and are now found in all of the Great Lakes and Lake Champlain, and in large portions of the St. Lawrence, Ohio, Mississippi, Arkansas, Tennessee, Hudson and Cumberland rivers. They also are found in numerous inland lakes in the New York and the upper Midwest The spread of invasive mussels from one lake to another can occur via connecting waterways or through recreational boaters, according to Alan Herlihy, an OSU research professor in the Department of Fisheries and Wildlife.

If people put their boat into a lake with these mussels one weekend, then take their boat out and put it into a different lake the next weekend, they may be transporting live mussel larvae or adults, Herlihy said. There are indications that adult mussels can live for many days out of water especially if the weather is cool and wet.

These invasive mussel species have caused millions of dollars in damage and untold ecological damage. Zebra mussels attach to hard surfaces with sticky threads called byssus. They also attach to, and weigh down, native freshwater clams and mussels, crayfish and even large aquatic insects like larval dragonflies. When they attach to native clams and mussels, the researchers say, these invasives compete directly for food. They also often attach in large numbers to all sorts of human structures, including water intakes which they quickly clog as well as boats, buoys, motors, and engine cooling systems.

2010

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Part 1: Reading about the data Read the following paragraphs, written by the researchers, about how they collected the zebra mussel data over a long period of time. Then, answer the questions that follow. These data are annual means of several important ecological variables for the growing season (May 1- September 30) for the freshwater tidal Hudson River in eastern New York State. They were collected as part of a long-term study of the Hudson River ecosystem by researchers at the Cary Institute of Ecosystem Studies, started in 1991 and continuing today.

Populations living on hard bottoms are sampled by a diver, who collects 10 rocks at each of 7 sampling sites in June and again in August. These rocks are returned to the lab, where zebra mussels are counted and the projected area of the rock estimated by tracing its outline. We identify, count, measure, and weigh all native unionid bivalves, continuing our long-term study of these animals and their response to the zebra mussel invasion (Strayer et al. 1994, Strayer and Smith 1994, 1996).

Phytoplankton are sampled weekly at our long-term station near Kingston throughout the year and in 2 sets of spatially distributed samples. We sample phytoplankton and many other variables (see below) at 6 “cardinal stations” arrayed over 120 km of the Hudson 4-6 times per year. In addition, 4-6 times a year, we sample phytoplankton and basic water chemistry and clarity every 2-4 km along the entire freshwater tidal Hudson River. Answer the following Questions:

1. Why do you think long-term monitoring of ecosystems is important? 2. What are the variables in this research project? 3. In order to have an idea of how many zebra mussels exist in the Hudson River, what would be better: to collect 10 rocks at 7 sites, 70 rocks at one site, or 2 rocks at 35 sites? ____________________Why? ___________________________________

___________________________________________________________________________________________________ Why do you think the scientists involved in this study decided to collect 10 rocks at 7 sites? _________________________

___________________________________________________________________________________________________ Part 2: Organism Changes Use the graphs below to answer the questions that follow. Densities of zebra mussels and unionid mussels are given in number per square meter, averaged over the freshwater tidal Hudson (RKM 99-248); data collected in August for zebra mussels and July for unionids. Scientists began collected unionid data in 1991. One meter squared equals ten square feet. 1. Why was the zebra mussel population at zero for the first part of the graph? _____________________________________________

2. When did the zebra mussel population increase? __________________________________________________________________

3. Describe the changes within the zebra mussel population since their arrival. _____________________________________________ __________________________________________________________________________________________________________

4. What happened to the native mussel population after the zebra mussels arrived? _________________________________________ __________________________________________________________________________________________________________

5. Why do you think the zebra mussel population goes up and down over time? ____________________________________________

Time (Year)

Unionids are a family of freshwater mussels

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__________________________________________________________________________________________________________

8. Based on this graph of water transparency and zebra mussel population, what can you conclude about the effects of the invasion? ____________________________________________

What factors affect the transparency of the water? ____________ __________________ What else would you need to know before deciding if the invasion of the zebra mussels affected the transparency of the water? _______________________________

9. Using this second graph, explain how the chemistry of the Hudson River changed over time. _________________________ ___________________________________________________ What relationship between the changes in the chemistry and the zebra mussel population do you see? _____________________ ___________________________________________________ ___________________________________________________

10. The introduction of the zebra mussel involves both Abiotic (Density-Independent) and Biotic (Density-Dependent) Factors.

a. Circle the abiotic factor that started this problem (Weather, Natural Disaster, Seasonal Cycles, Human Activity) Explain _______________________________________________________________________________________________ ______________________________________________________________________________________________________

b. There are potentially two biotic factors that have allowed them to be so successful in the freshwater of United States. Underline the one they do well and circle the one that is missing for them. (Competition, Predation, Parasitism, Disease)

Explain (“do well”)______________________________________________________________________________________ ______________________________________________________________________________________________________

Explain (“missing”)______________________________________________________________________________________

Cladocerans: small crustaceans, commonly

referred to as water fleas.

6. Both Cladocerans and Zebra Mussels feed on phytoplankton found in the river. Based on the graph above, what conclusion can you draw about the relationship between the native cladoceran population and the invasive Zebra mussels? _______________________ _________________________________________________________________________________________________________

7. Cladocerans are also a food source for other organisms in the river. These mussels are extraordinarily prolific. A female zebra mussel may produce a million eggs a year, and when they establish a colony, they are hard to get rid of. They also filter huge volumes of water, and by consuming phytoplankton (microscopic aquatic plants) they can dramatically change the aquatic food web of the lake, reservoir or river. Based on the graph above, what consequences might these changes have on other parts of the Hudson River food web? ____________________________________________________________________________________ _________________________________________________________________________________________________________

Time (Years)

Den

sity

of Z

ebra

Mus

sels

(per

m2 )

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______________________________________________________________________________________________________ a. Make a claim that answers the question. b. Give four pieces of evidence: 1. One piece of evidence from the text 2. One piece of evidence from the map 3. Two pieces of evidence from the graphs c. Justify the use of your evidence - tie the evidence together with your claim.

Question: What are the implications of introducing an invasive species into a new area? Claim: Evidence: 1. Textual: 2. Map: 3. Graph __________________________________ 4. Graph __________________________________

Justification of Evidence:

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