Presence of Zebra Mussels in Vermont

Introduction

 I remember looking intently at the small trick bike hanging on the wall covered in what appeared to be mud and shells. I ran my hands over it, even though there was a sign that said, “Do not touch.” The bike was rusted and covered in what I now know to be zebra mussels. When I was younger, I visited a place called the ECHO, Leahy Center for Lake Champlain. It is a museum/aquarium located on the lakes shore and is filled with interactive activities for families. They have an Invasive Species exhibit and zebra mussels are in it amongst others. I grew up in the state of Vermont only about 15 minutes away from Lake Champlain, which is a large lake located between the northern parts of Vermont and New York. Zebra mussels or Dreissena Polymar are considered the most aggressive freshwater invader in the northern hemisphere. (Karateyev, 2015) They are a common invasive species known to many great lakes around the country. There are many issues with zebra mussels positively and negatively effecting the ecosystems, economics, and social environment of the lake.

Background

An invasive species is a non-native organism that is introduced to an area harming and affecting the biodiversity of an ecosystem and the native organisms within that area. Invasive species can be introduced to an area in numerous ways one of them being from humans. In the case of Lake Champlain zebra mussels were introduced through humans who boat and angle in the lakes and waterways. (Mulhollem 2018) There are a lot of fishing competitions on the lake and people from other states will come to fish, their boats have bacteria from other waterways that introduce zebra mussels especially if they are not rinsed off properly. Zebra mussels are an issue in waterways for many reasons. One reason is that they can regenerate in large amounts compared to native mussels. They simply release larvae into the water column whereas a native mussels larva has to attach to a fish in order to reproduce. Zebra mussels can regenerate 30,000 eggs per year. (Cobban, 1991) They clump together on underwater objects as well as intake pipes causing large issues with the companies that have those pipes. Whereas freshwater mussels burrow into the lake bottom. Another concern with zebra mussels is that they smother the shells of other mollusks and compete with them for food. (Ricciardi, 2002) Groups of scientists in Vermont have done studies on the population ecology of zebra mussels and how other animals’ prey on zebra mussels. There is also the Lake Champlain Zebra Mussel Monitoring Program were findings from studies done by divers and scientist can be applied to create solutions. There are current solution options to rid zebra mussels and solutions already put in place for Lake Champlain.

Environmental Impacts and Benefits

Zebra mussels benefit the Lake Champlain environment by being prey to many of the native fish in the lake. Zebra mussels don’t have many of their own natural predators. Scientists completed a study in 2008 on fish in different locations amongst the lake and studied their predation on zebra mussels. They used a remote operated vehicle to film the fish in the early morning and late afternoon when fish are active. They took data from Bulwagga and Stave Bay, locations shown in Figure 1. Finally, they examined gut contents from a total of 698 fish across four species. The results showed that zebra mussels were a crucial part of the Pumpkin Seed fish diet by being 70% of its diet. (Watzin, 2008) They found that fish didn’t consume zebra mussels in the northern parts of the lake for example the Freshwater Drum had 59% of its diet consisting of zebra mussels but only within the southern portions of the lake. (Watzin, 2008) Over all zebra mussels provide a form of food for fish and this can be due to the fact that invasive species alter preferred food options for many native species.

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Zebra mussels seem like they can benefit the environment because they are filter feeders, so they filter sediment in the water column. However, when they filter the water, they filter food that is necessary for other organisms in the lake to eat such as plankton, since the introduction of zebra mussels Lake Champlain has seen measurable declines in phytoplankton biomass. (Watzin, 2008) There are only seven native mussels in Lake Champlain and they are currently at risk because of zebra mussels which suffocate them by multitudes attaching to native mussel shells making it difficult for them to open and collect their own food. Freshwater mussels are an important part of the ecosystem because they are considered “ecosystem engineers” where they alter habitats for other organisms and algae is able to stick to its shell. They also release nutrients that other organisms can intake. (“Important of mussels”, 2018) Currently there has been a drop in freshwater mussel population and zebra mussels are altering the lakes ecosystem. (Allaire, 2007) Significant loss of native mussels can lead serious issues within the food chain and the organisms who rely on them.

Another environmental impact that comes with zebra mussels is their ability to reproduce in great amounts. As mentioned earlier they release larvae into the water column unlike native mussels where they attach to fish. (Cobban, 1991) This is the forefront of the many issues involving zebra mussels. They are also able to refuge from predation and have protection from disturbances such as wave action by the creation of interstitial spaces among shells. (Beekey, 2004) A study was done in Lake Champlain researching the population of zebra mussels within the lake in different bay locations, Hawkins Bay and Appletree Bay also seen in Figure 1. Each bay has different characteristics. Hawkins has a muddy bottom and is sheltered. Appletree has a sandy bottom and is exposed to high winds. The difference in environment allows for a variety of data. Scientists studied zebra mussel densities in the sediment of the bays. Hawkins Bay saw 38,172 individuals and Appletree bay saw 31,312 individuals. (Beekey, 2004) These are large amounts of mussels because they can reproduce so easily. It also shows that they prefer a muddier sediment that is sheltered from wave action and strong winds. It was also found that dissolved oxygen was much higher in bare sediment than sediment containing zebra mussels in both bays. Dissolved oxygen is good for freshwater fish because they use it to breathe through their gills. It is also important for keeping good water quality so it is not beneficial that zebra mussels make it so there is less dissolved oxygen in the water. They also consume large amounts of algae which is a source of oxygen for fish, so their presence can cause little amounts of oxygen. Also, zebra mussels that coat sediment floor multiple inches thick can make it difficult for fish to find food on the lake floor. (McCabe, 2015)

Social Impacts and Benefits

Lots of people in Vermont enjoy fishing whether it is for sport or recreation. Fishing season is all year round with lots of people ice fishing in the winter. Zebra mussels can have a social impact on Lake Champlain because they can drive fish species out of an area or cause them to die. Zebra mussels intake lots of plankton and food opportunities in the water column for other fish. (Karateyev, 2015) This would cause fish to visit that part of the lake less frequently because there are scarce food resources. Thus, making it more difficult and unsuccessful for people to fish because fish are no longer in areas they were before.

Personal experience with zebra mussels as well as the ECHO Leahy Center for Lake Champlain are great opportunities for citizens to learn more about the invasive species issue. A social benefit of zebra mussels in the lake is that people in the Burlington, Vermont area can recognize this issue because it affects organisms on a local level. Many people may not have known about zebra mussels or their affects until they heard about them from fisherman, the news, even museums like ECHO. I wouldn’t have known about their existence in Lake Champlain if I hadn’t seen the exhibit on them on my school field trip. Also, the more people are aware of the species the easier it is to prevent them from showing up in different areas of the lake.

Economic Impacts and Benefits

Salmon fishing is popular for recreation and personal consumption. While it is illegal to sell any game fish in Vermont according to Vermont Public Radio, many families and the local economy could benefit from better Salmon. (Cengeri, 2015) Zebra Mussels can in fact contribute to the growth of fatter more desirable salmon. This was discovered in Lake Ontario in Ontario, Canada and shared by National Public Radio. Zebra mussels filter lots of algae out of the water column therefore making once mucky water, clearer. Salmon prey on a smaller fish called alewife and alewife prey on bottom dwelling shrimp. Since these fish hunt primarily by sight, clearer water means the shrimp have a difficult time hiding from the alewife when the sun is up because it is easier for the fish to see them. Ultimately the alewife eats more shrimp and the salmon eat more alewife making them fatter. (Nielson, 2008) While this hasn’t been studied in Lake Champlain there is a possibility for this to happen along with an increase in people paying to visit the area and purchase fishing equipment or licenses benefiting the local economy.

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One large impact the zebra mussel has on communities is that they clog and block water intake pipes for buildings. Due to their staking ability on any surface they stack together blocking water from entering the pipe. This poses threat to dams, buildings, and hydro plants from closing. If these places do close down it can hurt local Vermont economy since people will be put out of work and less energy supply is available for the surrounding communities. Zebra mussels also negatively affect tourism on the Lake Champlain beaches. Zebra mussels have sharp shells that get washed up to the shore and their decay creates an unpleasant odor. (Allaire, 2007) This causes visitors to not want to visit and pay the money to park which is important for the economy and to pay for the employees, snack bar, and bathrooms on the beaches. (Michael, 2018). Historical artifacts in the lake are also being ruined by zebra mussels, threatening sunken ships. The Lake Champlain Maritime Museum preserves nine Vermont vessels and one New York vessel. These vessels are open for divers to explore but one day may no longer be there. The mussels are putting strain on the wooden decks of the boats which are now water logged. The mussels lay two-three inches thick on the boat’s surfaces. (“Zebra Mussels Threaten Sunken Ships in Lake Champlain, Vt.”, 2018) As these vessels decline there will be a decrease in divers who spend money to be in Vermont and on their equipment to explore the underwater vessels which could harm the local economy.

Discussion

There are little solutions to solving the invasive zebra mussel issue. However, there are some options. Removal of zebra mussels from the lake would be expensive and can be difficult. Mechanical removal of the mussels would cost around $150,000-$200,000 every two years. (Shaefer, 2010) Chlorine treatment into pipes is the most common way, but it poses risk for leakage of chemicals into the lake. It also doesn’t eradicate zebra mussels only harms the ones that are there, so it must be consistently used. Zebra mussels can adapt to environment easily, so once chlorine is sensed they close their shells for long periods of time if necessary. (Sarrouh, 1998) Chemical treatment is subjected to cost $63,000 with less than $100,000 a year in operating cost. (Shaefer, 2010) Another solution being tested is using sparker pressure pulses to remove zebra mussels that are blocking pipes. In an experiment the sparker was placed in a wet well at the exit of an intake pipe for a paper towel and tissue mill in Lake Champlain. An electrical pulse was released and reacted with the water creating two pressure pulses. It was found that this not only eradicated adult mussels it prevented larvae from settling. (Shaefer, 2010) This system coats $60,000 and less than $5,000 a year for operation. (Shaefer, 2010) Sparker pressure is the cheapest option out of three mentioned above which is why it is being considered. Vermont Fish and Wildlife shares what citizens should do to avoid the spread of zebra mussels in a statement saying, “Make sure that all gear is drained, clean, and dry before entering and upon leaving a waterbody, and let gear dry as long as possible in the sun before moving it from one waterbody to another.” (Mulhollem, 2018) Also, The Sea Grant Lake Champlain states, “know the facts… be a part of the solution inspect, remove, drain, dry” (“Aquatic Invasive Species | Lake Champlain Sea Grant”, 2018) The Sea grant aims to prevent the spread of invasive/unwanted species during fishing tournaments by spreading the information. Very few water droplets are needed to contain juvenile zebra mussels, so it is important to dry equipment off to prevent the spread of the species. This is the current and common solution many sources are putting forth in Vermont because it is something everyone can do. (“Zebra Mussel Monitoring Program | Department of Environmental Conservation”, 2018) The Lake Champlain Zebra Mussel Monitoring Program continues to research and examine the species within the lake providing updates on their website to make sure the lake remains in good health.

Conclusion

There are many issues with zebra mussels positively and negatively effecting the ecosystems, economics, and social environment of the lake. Zebra mussels harm more than they benefit organism and the community proving this species is invasive and unwanted. It is necessary to have a healthy lake and keep native mussel species alive. The water column needs to be filtered properly as well as intake pipes being able to successfully extract lake water. Zebra Mussels are able to substantially reproduce so the less there are in Lake Champlain the better.  There are solutions available such as the sparker pressure pulses which is a cheap option but educating the community on what they can do to prevent zebra mussels is what is being implemented. The Burlington Free Press recently shared that the Lake Champlain Monitoring Programs test plates were pulled up and entirely lacked Zebra Mussels in the sediment sample. (McCabe, 2015) Right now zebra mussels are harming Lake Champlain but there has been a decline of population of the recent years to it is essential that this trend continues to preserve the health of the lake.

Citations

Karatayev, A., Burlakova, L., Mastitsky, S., & Padilla, D. (2015). Predicting the spread of aquatic invaders: Insight from 200 years of invasion by zebra mussels. Ecological Applications, 25(2), 430-440. Retrieved from http://www.jstor.org/stable/24432313

Ricciardi, A. (2002). Impending extinctions of North American freshwater mussels (Unionoida) following the zebra mussel (Dreissena polymorpha) invasion. Retrieved from https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2656.1998.00220.x

Cobban, B. (1991). Z-E-B-R-A Spells Trouble for Treatment Operators. Opflow, 17(10), 1-6. Retrieved from http://www.jstor.org/stable/43275422

Sarrouh, S. (1998). Mussel Relief: A Strategy for Coexisting With Zebra Mussels. Opflow, 24(9), 6-7. Retrieved from http://www.jstor.org/stable/43276437

Important of mussels. (2018). Retrieved from https://www.dnr.state.mn.us/mussels/importance.html

Michael, H. (2018). Lake Champlain Basin Program Fact Sheet. Retrieved from http://www.lcbp.org/wp-content/uploads/2013/03/Zebra2007.pdf

SCHAEFER, R., CLAUDI, R., & GRAPPERHAUS, M. (2010). Control of zebra mussels using sparker pressure pulses. Journal (American Water Works Association), 102(4), 113-122. Retrieved from http://www.jstor.org/stable/41313900

Zebra Mussels Threaten Sunken Ships in Lake Champlain, Vt. (2018). Retrieved from https://www.necn.com/news/new-england/Invasive-Zebra-Mussels-Threaten-Sunken-Ships-in-Lake-Champlain-Vermont-495837271.html

Aquatic Invasive Species | Lake Champlain Sea Grant. (2018). Retrieved from https://www.uvm.edu/seagrant/aquatic-invasive-species

Neilsen, J. (2008). NPR Choice page. Retrieved from https://www.npr.org/templates/story/story.php?storyId=87843464

Mulhollem, Josh. “Zebra Mussels Still A Threat To Vermont | Vermont Invasives”. Vtinvasives.Org, 2018, https://vtinvasives.org/news-events/news/zebra-mussels-still-a-threat-to-vermont. Accessed 15 Nov 2018.

McCabe, D. (2015). Zebra mussels: Good, the bad and the ugly. Retrieved from https://www.burlingtonfreepress.com/story/news/local/2015/10/02/zebra-mussels-champlain-invasive/73177896/

Zebra Mussel Monitoring Program | Department of Environmental Conservation. (2018). Retrieved from https://dec.vermont.gov/watershed/lakes-ponds/aquatic-invasives/monitoring/zebra-mussels

Watzin, M.C. (2008). “Significant fish predation on zebra mussels Dreissena polymorphain Lake Champlain, U.S.A.” Willey Online Library Retrieved from https://doi.org/10.1111/j.1095-8649.2008.02033.x

Beekey, M.A. (2004) “Zebra mussel colonization of soft sediments facilitates invertebrate communities” Willey Online Library https://doi.org/10.1111/j.1365-2427.2004.01207.x

Cengeri, R. (2015). VPR Cafe: Delicious Fish From Lake Champlain. Retrieved from http://digital.vpr.net/post/vpr-cafe-delicious-fish-lake-champlain#stream/0

Figure 1: Bay locations along and within Lake Champlain