- Angela DePalma-Dow
- Posted On
Lady of the Lake: Preventing invasive mussel introductions, part one
Dear Lady of The Lake,
I am an avid fisherman and moved to Lake County to enjoy my retirement fishing on Clear Lake. I recently purchased a bass boat and had to purchase a Lake County quagga mussel sticker. I don’t know much about these mussels or what would happen if they got into our lake. Can you provide some information so I can make sure we are doing all we can to protect Clear Lake?
Thanks,
Frank the fisherman
Dear Fisherman Frank,
Thanks for this very important and timely question. This is a question I get asked about quite frequently, and I am glad to be able to “dive” into this topic in breadth. Since this topic is so important, I will be writing about it in two columns.
In part 1, we will discuss the origins of invasive mussels, how they came to the United States and what it would mean for Clear Lake should an invasive mussels become introduced or established in the Lake, or any Lake County water bodies.
In my next column, part 2, I will describe our prevention program and how it works and how we can all help keep invasive mussels out of Clear Lake. Lastly, we will talk about what would happen if we got an introduction into Clear Lake, and the County of Lake’s current plans for a rapid response, control, eradication and containment plan. There is even a way for the public — you! — to be involved in the planning process.
Before we go further, let’s be clear about what defines an invasive species. According to the US EPA Watershed Academy, an invasive species is defined as “ A species that is not native in origin, whose presence in the environment causes economic or environmental harm or harm to human health.”
A non-native species that becomes introduced, or brought into a new environment, but does not successfully reproduce and become prolific is not considered an invasive species.
A non-native species that is introduced into a new environment, and successfully reproduces, and those offspring reproduce, is also not considered an invasive species. For this last one think about the Florida Black Bass in Clear Lake, who are successfully established and whose presence is a benefit to the local economy.
For a species to be really considered invasive, they must be introduced into a new environment, successfully reproduce, thrive, and cause some damage to native species, the environment in general, cause economic negative impacts, or cause human or public health impacts.
We will discuss how invasive mussels will impact the environment, or ecology, of Clear Lake, and the local economy. Invasive mussels can indirectly impact human health.
As an example, an invasive species that facilitates public health or human harm can include the invasive creeping water primrose that stagnates channels and coves and creates habitat havens for West Nile mosquitoes. Invasive species that directly cause human harm are perfectly exemplified in the several invasive mosquitos that carry and transmit diseases such as the Asian tiger mosquito (Aedes albopictus) that can transmit West Nile and Dengue fever.
In this case, invasive mussels as demonstrated in other aquatic systems, where they have been introduced and established, have caused impacts on all three facets of the US EPA definition.
Where invasive mussels are native
Invasive mussels, or specifically Quagga (Dreissena rostriformis bugensis) and Zebra (Dreissena polymorpha) mussels, are freshwater mussels in the Dreissenidae family. I will refer to these mussels as invasive dreissenid mussels. They are relatively small mussels and at a maximum cna grow up to 2 inches. They are shaped like a “D”, with a straight edge and striped shells, with black, gray, brown and white patterns — hence the reference to zebra common name.
Dreissenid mussels are native to lakes and tributaries in the region around southern Russia, Ukraine, Georgia, Romania, and Uzbekistan in water bodies such as the Black Sea, Sea of Azov, Caspian Sea, and Aral Sea. While there are fish and diving ducks native to the eastern european region where Dreissenid mussels are from, there are not the same predators in North American waters where these mussels have been introduced. Some natural predators of dreissenid mussels have also been introduced to North America, but they don’t prey upon the mussels like they do in their native habitat.
The round goby fish is an example, as it’s a species native to the eastern european waters alongside dreissenid mussels, where they are a main food source. Round gobies have been introduced into the Great Lakes, yet they are a food source for many native and invasive species, which keeps their abundance regulated. Round gobies have also been shown to prefer to forage on native north american mussels compared to their homeland’s Dreissenids.
How invasive mussels got to the United States
Invasive dreissenid mussels were introduced into North America through transatlantic freighter ships that started their voyage in the Black Sea and traveled across the Atlantic and through the St. Lawrence Seaway channel and lock system between US and Canada and into the Great Lakes.
From the Black Sea, freighter ships would drop off and pick up goods while also picking up water in their ballast tanks. Large ships use ballast tanks, which are large holding tanks with pumps, to balance loads and distribute weight evenly across the vessel, to ensure stability and safety when the ship is traveling and when they are loading or unloading cargo.
Ships leaving the Black Sea would travel through the Turkish Straits, a system of international water passages that connects the Black Sea ultimately to the Mediterranean Sea and then the Atlantic.
Once the ships had crossed the Atlantic, to gain access to large, safe ports of Canada such as Quebec City, Toronto, Hamilton, and Thunder Bay and US ports such as Toledo, Chicago, Duluth-Superior, Thunder Bay, they would have to enter the St. Lawrence River and into the man-made channel and lock system of the Great Lakes St. Lawrence Seaway.
The system of Canadian and US locks, canals, and channels has several locations where ships have to raise and lower to be level with the seaway, and at each of these junctions, they can release and take on water in their ballasts, to balance their load and adjust the weight of their ship. Likewise, any stops at ports along the Seaway, or within any of the Great Lakes, would require a release and intake of ballast water, to adjust as loads are changed.
During all this movement of water coming and going from a ship’s ballast tanks, there is ample opportunity for aquatic invasive species, that have been picked up in the ballast water from the ships point of origin — or anywhere else along their route — to be released into the “new environment” during a ballast adjustment.
Normally, and obviously, freshwater species and saltwater species don’t occur in the same habitat, so one way for freighter ships to prevent the spread of invasives along transatlantic routes is to implement ballast water management. The requirements are designed by the International Maritime Organization or IMO. The US governmental arm that participates in the IMO is the Shipping Coordinating Committee which is part of the Office of Ocean and Polar Affairs within the State Department.
Besides invasive dreissenid mussels, proper ballast water management programs have been successful in preventing the spread of other threatening and dangerous invasive species such as Asian Kelp, cholera, European green crab, and North Pacific seastar. Each of these species, in areas where they have been introduced and established, have caused significant economic and ecological harm, and in the case of cholera, significant human harm.
Invasive dreissenid mussels, once introduced into the Great Lakes, found suitable habitat in the freshwaters that were similar in latitude and habitat to their native waters. Once established in an area, they proliferated throughout the entire watershed, downstream throughout the Mississippi Basin, the Ohio River, and throughout the midwest, eastern seaboard, and into the Southern United States.
While it’s unknown when the first introductions took place, the first detections of mussels occurred in New York in the 1980s. By the 1990s mussels had been found west of the Rockies and the first detection in California occurred in 2007 in several border counties in southern California.
Invasive dreissenid mussels spread throughout non-connected water bodies on trailered boats overland. While adult mussels are sessile and attach to substrates and structures in water bodies, the juveniles, called veligers, are free floating in the water column and can survive in very small amounts of water that doesn’t get above 120 degrees F. Any boat or watercraft that has a compartment or space that holds water, could potentially be moving veliger - mussel - infested water over land.
Once a veliger, or adult mussel is introduced to a new water body, and the local water conditions are suitable, they can easily reproduce and a population is therefore established.
A single mussel can produce a million gametes sometimes up to six times a year. When fertilization occurs in the water column, the fertilized zygote turns into the larvae stage of a juvenile mussel, called a veliger. While the individual number of veligers that survive is low, the abundance of gamete production ensures high reproductive rates and lakes that were previously uninfested, quickly transform once the mussels spread.
Impacts of invasive mussels
Invasive Quagga and Zebra mussels, if introduced into Clear Lake, would cause significant negative impacts. These impacts can be divided into ecological, economical, and public health. And some impacts overlap more than one category.
For example, invasive dreissenid mussels are filter feeders, removing green algae from the water column, sometimes up to 3 liters a day. Green algae is the base of the food web in fish-dominated lakes like Clear Lake. Drastic changes to the food web will impact the current lake ecology and the local economy that depends on current lake ecology - like the presence of large and abundant game fish like catfish, black bass, and crappie.
Green algae are consumed by zooplankton (small aquatic insects or copepods) which is the main food source for small bait fish, like minnows, shad and sunfish. Larger game fish can consume both bait fish and zooplankton. Almost all small, juvenile fish feed off both green algae and zooplankton. If Invasive dreissenid mussels were introduced into Clear Lake, they would significantly disrupt the base of the food web, with high probability of causing a fishery decline or crash.
This effect has been identified in other aquatic ecosystems with most impacts occurring to recreationally and commercially important species. For example, in Lake Ontario, following Zebra mussel introduction, Lake Whitefish and Walleye populations declined and recruitment reduced as the mussels compete directly with preferred fish food.
Some local myths exist that suggest that mussels would “clear up the water” and “take care of our harmful algae problem” in Clear Lake. Unfortunately, lab and field studies have demonstrated that this would not be true. Laboratory studies have shown that dreissenid mussels selectively eat green algae (phytoplankton) as opposed to cyanobacteria (which is the category of organism responsible for creating harmful algal blooms in Clear Lake).
Specifically, the dreissenid mussels will spit out the cyanobacteria, and only metabolize the green algae. And since cyanobacteria are not fish food, we will see declines in food available for fisheries, and more space and resources available for cyanobacteria as the valuable green algae declines.
One just has to look to Toledo, Ohio, located on Lake Erie, which has an abundance of invasive dreissenid mussel populations and worsening annual cyanobacteria blooms, to understand that the presence of invasive dreissenid mussels does not benefit water quality.
Invasive dreissenid mussels can have direct impacts to the economy through their disruption to drinking water systems. Clear Lake provides drinking water to about 60% of the Lake County population via 17 private and public drinking water purveyor systems. Intakes located within the lake could suck in juvenile mussels, or veligers.
Once inside the drinking water intake infrastructure, the dreissenid mussels could settle and attach and eventually accumulate within the pipes reducing the available space for water volume. Additionally, the dreissenid mussels produce waste and as they die, the bacteria can contaminate the water headed to treatment, creating complications for treatment systems. This is where invasive dreissenid mussels could heavily harm human health and could cause public health concerns.
As dreissenid mussels in drinking water pipes die, they decompose and the bacteria, smells, and particulates within the systems would lead to cost increases to produce safe drinking water. And if the water couldn’t be treated adequately, the system would have to be purged, wasting millions of gallons of Clear Lake water. The time, staff, tools, and effort needed to remove the mussels from the infrastructure within the lake would also be expensive.
All these costs would be passed down to the consumers, or residents of Lake County. I would further suggest that the costs associated with mitigating invasive dreissenid mussels in drinking water would bankrupt some of the smaller water treatment systems, as water rates from Clear Lake are already the 3rd highest rate in the state.
Additionally, invasive dreissenid mussels can cause economic impacts by their contribution to the decrease in recreational value in freshwater lakes. Dreissenid mussels grow exponentially and when they die, their sharp shells can accumulate on beaches and shorelines causing difficulty for people and animals to safely access the water.
Some beaches in Michigan, and other states, that have miles of dunes composed of sharp, dead mussel shells, are basically abandoned, and can’t serve any recreational purpose. Businesses that rely on that water access struggle to survive and stay afloat.
Adult mussels can also settle and attach to any structure in the water, including ramps, docks, anchor lines, and boat hulls and propellers. Imagine having to laboriously scrape your boat hull of mussels twice a year, or not being able to launch your kayak on your ramp because it’s covered in sharp mussels.
This is the reality of people with lakeside properties that live on mussel-infested lakes and could be the fate of Clear Lake shoreline residents should mussels become established in our lake.
To be continued…
I hope you learned a little bit about invasive dreissenid mussels, Fisherman Frank. I hope you read my next column, where I will focus on our Invasive Mussel Prevention Plan and Program, including how the stickers work to prevent mussels in our lake and how the ramp monitors are key in the prevention program.
Also in my next column, I will discuss what is being planned at the County of Lake Water Resources Department, should an invasive mussel make it to Clear Lake and a population establish. The goal is to maintain Clear Lake ecology so that we can maintain our way of life, and prevent the spread to other northern California lakes.
If you wanted to learn more about the current prevention program, you can visit the County of Lake Invasive Mussel webpage at www.nomussels.com.
To learn more about Invasive Dreissenid mussels in general, you can visit very user-friendly and interactive Invasive Mussel Collaborative website here: https://invasivemusselcollaborative.net/.
Sincerely,
Lady of the Lake
Angela De Palma-Dow is a limnologist (limnology = study of fresh inland waters) who lives and works in Lake County. Born in Northern California, she has a Master of Science from Michigan State University. She is a Certified Lake Manager from the North American Lake Management Society, or NALMS, and she is the current president/chair of the California chapter of the Society for Freshwater Science. She can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..
The County of Lake Water Resources Department wants to know what you know about invasive mussels! Take this 2-minute survey and get entered to win a FREE 2024 resident or visitor sticker for your boat (a $20 value!). You can access the survey from a computer, tablet, or smartphone at this link: https://forms.gle/5YRq5hPcAdR8NBm56