top of page

Preserving Lake Superior Water Quality

A Conversation with Phyllis Green On Ballast Water and Invasive Species

Ballast Water - Ore Ship - Taken By Christian Dalbec
Phot credit: Christian Dalbec

Lake Superior, the largest of the Great Lakes, is not only a majestic body of water but also a fragile ecosystem that is vulnerable to invasive species. One of the main culprits for the introduction of these species is ballast water, which is used by ships to maintain stability. When ships take on water in one location and discharge it in another, they inadvertently transport non-native species, such as zebra mussels and viral hemorrhagic septicemia, which can have devastating effects on the lake's ecosystem.


Phyllis Green, board member with the National Parks of Lake Superior Foundation and a former superintendent at Isle Royale National Park, recently shared her perspective on the issue with Lake Superior Podcast hosts Walt Lindala and Frida Waara. (Listen here!)


A severe and growing problem

The introduction of invasive species through ballast water has had severe consequences for Lake Superior, Green says, noting that when ships pick up ballast water it “becomes an aquarium, if you will, on the way over. And then when they discharge for cargo operations, they let loose these invasive species.”

The rapid spread of zebra mussels is one of the most prominent examples, she says. Zebra mussels spread so far and so fast they have clogged water distribution systems in the western states and disrupted the intake of water for crops. Additionally, lampreys, another invasive species, have required significant financial resources to control and prevent damage to the sport and commercial fisheries in the lake.


Furthermore, the issue extends beyond non-native species. Native species from the lower Great Lakes are also being transported to the colder waters of Lake Superior, disrupting the delicate balance of the ecosystem. It is clear the problem of invasives isn’t going away. Five new invasive species have been discovered in the lake in the past five years. The movement of these species highlights the need for comprehensive treatment of ballast water to prevent further damage.


Challenges in implementing filtering systems

While the need for ballast water treatment is evident, the implementation of effective filtering systems has faced numerous challenges. One of the main obstacles is the reluctance of the shipping industry to adopt chlorine-based treatment systems, Green says. Despite the widespread use of chlorine in water systems, the industry has concerns about its impact on ship safety. However, research has shown that lower doses of chlorine, combined with extended treatment times, can effectively treat ballast water without compromising ship safety.


Another challenge lies in the slow pace of regulatory processes. Recounting her experience in developing an emergency treatment system for the Ranger III, a ship at Isle Royale National Park, Green notes that the system was successful in preventing the spread of invasive species, but the approval process took years. The lack of clear regulations for emergency treatment and the slow progress in approving permanent treatment systems for lakers have hindered the implementation of effective solutions.


The need for stronger regulations

To address the issue of ballast water and invasive species, stronger regulations are necessary, Green states. Canada has taken a proactive approach by requiring lakers to install treatment systems and providing funding for research and development to overcome industry concerns. However, the lack of regulation in the United States creates an uneven playing field, with Canadian ships treating their ballast water while their American counterparts remain untreated.

Green has been actively involved in addressing the issue of ballast water and invasive species in the Great Lakes for more than 15 years and she is frustrated with lack of progress. "We're not doing it, and that's wrong,” Green says.

You can make a difference

By raising awareness and engaging with legislators, concerned members of the public can play a vital role in protecting Lake Superior from the devastating effects of invasive species.

NPLSF has been advocating for the implementation of treatment systems on all lakers and the establishment of an avenue for emergency treatment. Engaging with legislators and raising awareness about the importance of protecting Lake Superior's ecosystem is crucial in pushing for stronger regulations. 


NPLSF encourages concerned citizens to voice their support for ballast water treatment and to hold their elected officials accountable for protecting the lake. A copy of our recent comment letter to the US Environmental Protection Agency is available here. For more information, contact us at

Listen to the full episode on ballast water, invasive species, and Lake Superior—and stay tuned for more insightful discussions on the Lake Superior podcast.


About The NPLSF

The Lake Superior Podcast is a project of the National Parks of Lake Superior Foundation. 

NPLSF is the official 501(c)(3) friends group for Lake Superior’s national parks: Apostle Islands National Lakeshore, Grand Portage National Monument, Isle Royale National Park, Keweenaw National Historical Park, and Pictured Rocks National Lakeshore.


bottom of page