Shipwreck Preservation in the Great Lakes Faces Threat of Aquatic Invasive Species

Post by Ryan Smazal, Maritime Preservation Intern at the Wisconsin Historical Society, and Sara Fox, Aquatic Invasive Species Outreach Assistant at UW-Extension. Also on Wisconsin Sea Grant’s Great Lakes Takes.

As many people might know, the Great Lakes house about a fifth of the freshwater supply for the entire world. A less commonly known fact is that the Great Lakes contain more than 700 shipwrecks. Among those shipwrecks live over 3,500 plant and animal species who generally coexist with the shipwrecks in peace. However, the introduction and spread of aquatic invasive species might threaten existing ecosystems and the preservation of shipwrecks in the Great Lakes.

The Great Lakes were once a massively important trading region because of their connection to inland rivers and lakes which helped transport goods. The shipping industry took advantage of this connection, as well as the Great Lakes’ many natural ports. For various reasons, including gales, scuttling, and fires, some of the same ships from this era remain at the bottom of the Great Lakes today. Fortunately, the cold water and low salinity of the Great Lakes create an ideal environment for preserving these shipwrecks. Historians have interest in uncovering new shipwrecks as a way to investigate old trade routes, discover cargo, and study differences in ship design. Additionally, fish tend to make their homes near shipwrecks, so divers enjoy the opportunity to explore freshwater ecosystems.

The La Salle has been preserved at the bottom of Lake Michigan since 1874. Photo credit: Tamara Thomsen

Although new wrecks are being discovered every year, there’s concern to preserve the ones we’ve already found. An example historians look to is that of The Alvin Clark, a ship that began to deteriorate as soon as it was removed from its cold and wet home in Lake Michigan. Apart from the natural preservation system the lakes provide, there are intervention-related options for conservation such as polyethylene glycol treatment or designating a wreck as a National Historic Place. Unfortunately, options like these tend to be expensive and time consuming.

Despite efforts being undertaken to preserve the shipwrecks, they face a new potential threat: aquatic invasive species.  Today over 180 nonnative species, both plant and animal, inhabit the ecosystems of the Great Lakes. The vessel most likely responsible for the introduction of many of these invaders are cargo ships that enter through the St. Lawrence Seaway. Large cargo ships uptake water at the beginning of their journey to provide stability on the high seas. When the ships arrive to their destination and it’s time to make room for cargo, they release the necessary amount of ballast water, along with aquatic animals and plants that may have hitched a ride. Some of these foreign species die immediately, but those that survive can thrive due to their reproductive capabilities or lack of native predators.

Aquatic invasive species that might pose a threat to the preservation of shipwrecks include mussel species like the zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena rostriformis bugensis). Here’s why:

  • Zebra and quagga mussels begin their lives as microscopic veligers, slowly taking in nutrients and growing until they become heavy enough to sink. Once they begin to sink, they use feet-like assemblages called byssal threads to stick on to the first hard substance they encounter whether it be a boat propellor, a dock, or a shipwreck. Many mussels on the same structure could cause a heavy pile up, and sometimes can corrode certain metals.  
  • Both zebra and quagga mussels are filter feeders. Did you know a single zebra mussel can filter up to a liter of water a day? Mussel respiration also produces carbon dioxide. Both of these characteristics can affect water quality and alter waterbodies in a way that may not be favorable to shipwreck preservation.
  • Zebra and Quagga mussels reproduce quickly and in large quantities. A female zebra mussel can produce as many as one million eggs in a season! Once introduced to an area, invasive mussels can take over and continue to affect water quality and damage underwater structures for decades.

Zebra mussels piled up on an old tennis ball. Photo credit: Paul Skawinski

Even though there are over 180 kinds of nonnative species on the Great Lakes, we shouldn’t be discouraged. It’s important to still be conscious of the cleanliness of our watercraft vehicles.  Not every patch of every Great Lake has a zebra mussel presence and shipwrecks could exist in an acre of water not yet infested. Aquatic invasive species can be accidentally transported in boat motors, livewells, and on fishing and diving gear. Individual lake users can help stop the spread of invasive species by following the WDNR recommended prevention steps:

INSPECT boats, trailers, and equipment

REMOVE all visible plants, animals, and debris

DRAIN water from boats, motors, bilges, and live wells before transporting away from a water or entering Wisconsin

NEVER MOVE live fish away from a waterbody

If every boater were conscious of their ability to spread invasive species and took actions to prevent the spread, existing populations could be easily contained. If populations were contained forever, shipwrecks in uninfested areas could be preserved and studied for decades to come.

For more information about aquatic invasive species, consult the NAS database:

For more information about shipwrecks in the Great Lakes, consult:

Posted in Other | Leave a comment

How Lake Lovers Become Lake Leaders

Post by Carroll Schaal, Lakes and Rivers Section Chief for the DNR’s Water Quality Bureau; adapted by Sara Fox, UW-Extension

The waters and beds of natural lakes and streams in Wisconsin are considered Public Trust property – they belong to everyone. There are more than 15,000 lakes in the state, providing plenty of opportunity for the public to get involved in helping to manage those bountiful resources.

Many of the state’s laws and programs are intentionally designed to create public/private partnerships that enable citizens to play a central role in getting positive work done. There are laws that allow the creation of qualified lake associations and lake districts for the express purpose of raising funds and conducting projects to enhance, protect or restore lakes. There are cost-share programs that provide up to 75 percent of the cost of a project. There are volunteer programs where citizens monitor water quality and aquatic invasive species or educate boaters about the threats of AIS.

A partnership between natural resources agencies and local citizen-run organizations helps protect our lakes. Credit – DNR Files


In these programs, the DNR provides technical assistance, support, supplies and sometimes funding, while relying on citizens to carry out much of the work. Partnerships between natural resources agencies and local citizen-run organizations are essential to effective natural resources management.

This has long been the mode of operation for the Wisconsin Lakes Partnership. The partnership seeks to join the technical and financial resources of the DNR, the educational capacity of the University of Wisconsin Extension and the organization of Wisconsin Lakes Inc., a nonprofit serving local lake groups and interests – all to empower local citizen-led lake management.

There are thousands of citizens serving as officers, board members, volunteers or staff for the state’s 220 lake management districts and 500-plus lake associations, not to mention the counties, towns, cities and villages essential to maintaining and protecting these precious resources. However, few possess any formal training that prepares them for the host of complex issues they may face, whether it’s managing algae or zebra mussels, seeking grants or recruiting and directing volunteers.

In 1998, to address the need for leadership in this realm, Wisconsin began a program called the Lake Leaders Institute. Its charge was to “proactively develop a pool of committed and prepared leaders who could assume leadership roles in the Wisconsin lakes and other statewide committees, countywide lake associations and watershed teams being organized by the Wisconsin Department of Natural Resources.”

Today, the Wisconsin Lake Leaders Institute is a statewide program that helps lake stewards gain a better understanding of lake ecology and how to work with state and local governments to ensure lakes get the attention they need. The training program enhances skills and broadens capabilities of people in our lake communities, champions effective and communicative collaboration, and fosters responsive and useful networks that support lake citizens.

The LLI is designed to assist in developing and enhancing both the technical and the people skills of citizen leaders. To date, more than 320 individuals have “graduated” from one of the institute’s 11 “crews,” and Crew 12 launched in May. A new crew is recruited every two years.

A “dream team” of lake professionals has given program organizers a hand in educating and motivating lake leaders. Instructors come from all walks of the lake world: academia adept in leadership development and citizen advocacy support; research limnologists; government officials; not-for-profit leaders; Native-American educators; technical experts from assorted natural resources agencies at the federal, state, county and town levels; private-sector lake-related businesses; and Extension outreach specialists, among others.

In addition to lake residents, participants may include staff from the DNR, UW Extension, county conservation and zoning offices, and private consulting. The mix of agencies, staff and citizens creates a unique dynamic that naturally fosters the collaboration and partnering necessary to succeed in today’s environment.

How it works

To participate in the Wisconsin Lake Leaders Institute, crew members must be nominated. Though they can self-nominate, it’s much more effective and meaningful for candidates to be nominated by others who see their leadership potential.

Candidate nominations require a letter of recommendation and a detailed candidate application. The completed applicants are reviewed by committee and the top 30 are selected per class. Crew members must commit to attend and pay $300, covering about half the cost.

Instructors are mostly volunteer and venues are modest to help keep it affordable. Courses within each seminar are designed to create an atmosphere of openness, trust and camaraderie.The training program consists of three two-day seminars in May, September and October.

Lake Leaders Institute trainees get a crash course on the science and ecology of lakes. Credit – UWEX Lakes

The first session focuses on building a sense of camaraderie exploring values, ethics, perceptive communications, what leadership means and the philosophy and history of Wisconsin lake management. The second session is a lakeside crash course on the science and ecology of lakes, how humans impact lakes and the basic building blocks of a lake management plan. It includes an afternoon in pontoon boats learning how water quality, habitat and fish and aquatic life are measured. The final session focuses on organizations, people, politics and the law.

Graduation from the Lake Leaders Institute takes place at the Aldo Leopold shack on the grounds of the Aldo Leopold Foundation near Baraboo. There, graduates share a commitment statement describing how they will use their leadership skills to enhance the community in which they live and become active participants in protecting in partnership our legacy of lakes in Wisconsin.

Advanced training and awards

In addition to the regular LLI sessions, single-day advanced training sessions are offered to graduates in odd-numbered years to continue to keep leaders inspired and connected. Topics for these programs cover timely issues on the cusp of new techniques or roll out new programs being offered by the state. Even after nearly 20 years, these advanced training sessions are attended by members from all the past crews.

Evaluation surveys show high levels of satisfaction with what participants learn in the program, but almost everyone mentions the personal connections they made as equally valuable. Roughly three-quarters reported becoming more confident and more active in local lake management affairs and in their ability to influence decision makers.

Several LLI graduates have been inspired to run for a local elected office and, in terms of meeting the original goal, the board of Wisconsin Lakes also has been well-stocked through the program.

In 2009, the Lake Leaders Institute received a national award for outreach and education from the National Fish Habitat Board, a division of the National Oceanic and Atmospheric Administration. Among hundreds of nominees, the institute was chosen by the board for its “extraordinary commitment to fish habitat conservation, science and education.” 

With the help of the Wisconsin Lakes Partnership, the LLI should hopefully continue that commitment well into the future.

Posted in Lake Leaders, Lakes Partnership | Leave a comment

Much Ado About Mussels

Post originally by Phil Moy, formerly Wisconsin Sea Grant; adapted by Sara Fox, UW-Extension

Dreissena polymorpha (zebra mussel) credit: Paul Skawinski for UW-Extension Lakes.

Zebra mussels have spread to more than 250 Wisconsin lakes and rivers since being first being identified in 1986. These small mollusks colonize docks, floats and boating equipment; their sharp shells can injure swimmers. They form dense colonies, up to 65,000 individuals per square foot, that can interfere with water supplies, disrupt food webs and alter ecosystems.

Like many other recent Great Lakes invaders, the zebra mussel is native to the Baltic region of Europe and was carried to our shores in the ballast water of ocean-going freighters. Zebra mussels were originally introduced to Lake St. Claire in the mid 1980’s. Since then, zebra mussels have spread throughout the Great Lakes region, into the Mississippi River, down to the Gulf of Mexico and into Canadian waters. They are spreading to inland lakes in many states including Wisconsin.

How Do They Spread? 

Zebra mussels are prolific breeders; a single female can produce tens of thousands of eggs annually. Eggs and sperm are released into the water column. After fertilization, the microscopic larvae, called veligers, float about in the water column for up to a month. At that time, the larval mussel transforms into a juvenile and settles to the bottom. Once settled, it adheres to a hard surface by means of sticky fibers called byssal threads.

Zebra mussels are able to spread easily due to the planktonic larval form and the adhesive adult form. The larvae can be carried in bilge water, live wells, bait buckets, or anything else that holds water such as dive gear. The juveniles and adults can attach to any hard surface that is submerged for a prolonged period of time including boat hulls, floats, anchors and lines, piers, swimming platforms, rocks, wood and vegetation. Adults are easily seen with the unaided eye; juveniles feel like sand or grit on the surface of boat hulls, motor or other submerged parts. Larval mussels can only be seen with a microscope.

The larvae need to remain wet to survive, but adults and juveniles can live out of the water for several days. A boat carrying adult or juvenile zebra mussels on the hull, larval zebra mussels in the bilge, live well water or plants tangled on the trailer can easily introduce zebra mussels from one lake to another.

Environmental Effects

Zebra mussels are filter feeders; they filter planktonic food from the water around them. Each zebra mussel can filter a liter (over a quart) of water per day. As they feed, they remove plant and animal plankton from the water. These tiny animals form the first food for the larvae of many desirable fish and are the food for other native species. As zebra mussels take plankton from the water, they compete with our native species for this food. The juveniles and adults can attach to any hard surface that is submerged for a prolonged period of time. Zebra mussels also make the water clearer. Though we often think of clear water as better water, clear water means there is less food for our native plankton-feeding organisms. Clear water also makes it possible for submergent vegetation to grow in areas that were previously too turbid to allow plant growth. This can contribute to weed-choked shorelines and changes in the food web and fish populations.

Zebra mussels adhere to the exterior of a clam.

Preventing the Spread

Lakes are usually identified as being colonized only after the mussels have been present for some time, perhaps years. People using boats, personal watercraft and diving in these and other waters may have unknowingly been vectors for the spread of zebra mussels into other lakes. Likewise, lakes not yet known to be colonized may already have zebra mussels in them. For this reason we need to take precautions to prevent the spread of zebra mussels and other invasive species every time we plan to move from one lake or river to another.


  • Drain water from bilge, live wells and motor.
  • Remove weeds from trailer, rudder, centerboard, anchor, motor and other areas.
  • Rinse mud from anchor and line.
  • Dispose of live bait.
  • Remove plant parts from the intake and run personal watercraft and jet boat engines for a few seconds out of the water.
  • Let boats, trailers and equipment dry for 5 days before moving to new waters.

As you pull docks, swim floats, anchors, lines and boats from the water, look and feel for zebra mussels on surfaces that were submerged through the summer season. Juvenile mussels may not be easily seen, but will feel like grit on the surface. Larger mussels are easily seen and may occur in groups or as separate individuals. If you find zebra mussels in a lake not known to be infested, save some of the specimens and please contact Wisconsin DNR, UW Extension or Wisconsin Sea Grant at the numbers below.

Other Invaders

Zebra mussels are not the only invaders trying to find their way into our inland lakes and streams. Recently, round gobies were found in Little Lake Butte des Morts near Lake Winnebago; the spiny water flea, a large predacious species of zooplankton, has been found in a handful of lakes in northern and southern Wisconsin. If these and other species find their way into our favorite lakes they may forever alter the ecosystem as they already have in Lake Michigan.

Round gobies are invaders like zebra mussels that threaten inland lakes.

The AIS Attack Pack

Wisconsin Sea Grant has developed a self-contained teaching tool for K-12 educators that can be checked out from the Wisconsin Water Library.

Contact Tim Campbell ( for more details.

Posted in Other | Leave a comment

Passion and commitment of volunteers help protect lakes in western Vilas County

Emily Heald, Water Program Coordinator for the North Lakeland Discovery Center

In 2017, almost 200 volunteers in western Vilas County put in about 1,500 hours of time spent monitoring for aquatic invasive species, reviewing management plans, completing Clean Boats Clean Waters surveys at boat landings, and monitoring lake levels. It has all been a part of the 7-year partnership between the North Lakeland Discovery Center (a nonprofit environmental education center) and nearby towns of Manitowish Waters, Boulder Junction, and Winchester, as well as the Manitowish Waters Lakes Association and Winchester Town Lakes Committee. Our work consists of obtaining WDNR funding to create management plans on 24 lakes (spread over the years), with each project utilizing town financial donations and volunteer support for the matching funds required by the grants.

A proud group of folks from Winchester celebrate the CBCW program at a boat landing barbeque.

“We are hopeful that these projects will give us the knowledge and tools to ensure that we can prevent any potential invasive species contamination in the future through education and diligence by our lake property owners, as well as the recreational boaters and fishermen who visit the lakes.” (Gary Engstrom, Rock Lake)

For each project, multiple AIS identification trainings are held to give volunteers the skills to go out on their own time to monitor their lakes for AIS. Each project also holds at least two meetings open to riparian owners where results of studies are presented, and attendees learn about lake ecology.

We are creating a culture with lake property owners to be aware of, and routinely monitor, their lake and its environs.”(Rolf Ethun, Hiawatha Lake)

Some volunteers felt they were born into these projects from living on lakes their whole lives, while others join the cause through lake associations, after retirement, or by hearing about it through friends. However the sparked interest occurs, all volunteers overwhelmingly agree that it is “exciting and rewarding to see all the townships and lake associations work together” (Karen Dixon, Manitowish River) and “to see how everyone in the community has pulled together to solve the AIS problem” (Bob Becker, President of Manitowish Waters Lakes Association).

A lesson learned from this partnership? A little education can go a long way in “turning dock-loungers into caring citizen scientists-some a little and others a great deal” (Rolf Ethun, Hiawatha Lake).

Thank you to ALL of the volunteers who work together on these projects protect lakes and rivers.

Now, I’m hoping that working on invasive species issues I might be able to help leave an area be in better shape than I found it” (Greg Holt, Benson Lake).

Volunteers Al and Paul endure freezing temperature to monitor lake levels.


Posted in Other | Leave a comment