Microplastic debris found in the Great Lakes. Photo by National Oceanic and Atmospheric Administration.

When most people think about plastic pollution, images of floating bottles or ocean garbage patches often come to mind. But the plastic causing some of our biggest environmental concerns today is far smaller, often invisible to the naked eye, and it is right here in the Northland.

These tiny fragments, known as microplastics, are now found everywhere scientists look: oceans, rivers, lakes, sediments, wildlife and even the air we breathe.

In the past two decades, my research on microplastic pollution has progressed from marine systems to freshwater environments, sediments, organisms and interdisciplinary contexts. I have studied microplastics in environments ranging from the North Pacific Ocean, coral reefs and kelp forests to Antarctic waters and, importantly, Western Lake Superior.

What I have learned is both sobering and motivating.

What are microplastics?

Microplastics are pieces of plastic smaller than a grain of rice. They come from two main sources: Plastics intentionally made small, such as microbeads once used in cosmetics, and larger plastic items that break down over time due to sunlight, waves and mechanical wear. Synthetic clothing fibers released during laundry are also a major contributor.

Because plastics do not biodegrade like natural materials, they persist and continue to fragment. Once they reach lakes, rivers and oceans, microplastics can be transported long distances or settle into sediments, where they may remain for decades.

Lake Superior Is not immune

Lake Superior is often celebrated for its pristine waters and remote shoreline. Yet my research, conducted in western Lake Superior and the St. Louis River Estuary, in collaboration with my students and colleagues, revealed heterogeneous distributions of microplastics in sediments and surface waters, driven by hydrodynamics, watershed inputs and urban influence.

This research shows that microplastics are present in beach sands, nearshore sediments and surface waters along the western part of the lake.

The sources are varied – urban runoff, stormwater discharges, wastewater effluents and recreational activities all contribute. 

Wind and waves redistribute particles, creating patchy “hotspots” of accumulation. In some areas, microplastic levels in Lake Superior sediments are comparable to those measured in coastal marine environments.

This matters because freshwater bodies are not just endpoints – they are pathways. What enters Lake Superior does not necessarily stay there; it can move through connected waterways and eventually reach the ocean.

Why size matters

Microplastics are small enough to be mistaken for food by aquatic organisms. Fish, insects, mussels and even microscopic plankton may ingest them.

In studies conducted in freshwater and marine systems, microplastics have been found in the digestive tracts of species at all levels of the food web.

While the physical presence of plastic is concerning, what’s equally troubling is what microplastics can carry. Plastics attract and absorb toxic chemicals already present in the environment, including persistent organic compounds such as flame retardants and petroleum-related compounds.

When organisms ingest microplastics, they may also be exposed to the hitchhiking chemicals they carry.

From the ocean back home

Earlier in my career, much of my research focused on marine ecosystems, including the Gulf of California and the Pacific Ocean. These environments taught us early lessons about plastic accumulation and ecological risk.

It has become increasingly clear that freshwater systems like Lake Superior face many of the same threats but often receive less attention.

The scientific tools developed for ocean research – advanced microscopes, infrared spectroscopy, and contamination-control protocols – are now being applied locally.

At the University of Wisconsin-Superior and through collaborations worldwide and in the region, students are actively sampling rivers, beaches and sediments, contributing data that help clarify local conditions.

 Why this is a community issue

Microplastic pollution is not caused by a single action or industry. It reflects how we produce, use and dispose of plastics in daily life. Synthetic clothing, takeout containers, vehicle tires and packaging all leave a footprint that eventually reaches the environment.

That means solutions also exist at multiple levels. Policy changes, such as bans on certain plastic products, have already reduced some sources. Improved wastewater treatment, better stormwater management and responsible product design can make a meaningful difference.

Equally important is public awareness.

Communities like Superior-Duluth, with strong ties to water and outdoor recreation, are well-positioned to lead by example by supporting research, reducing unnecessary plastic use and advocating for sustainable infrastructure to support healthier aquatic systems.

Training the next generations

One of the most hopeful aspects of my work has been mentoring undergraduate and graduate students deeply committed to environmental stewardship. Many of them begin research projects expecting to confirm that our local waters are “clean,” only to learn how complex and interconnected pollution issues can be.

These students go on to careers in science, policy, education and conservation, carrying with them an understanding that environmental problems require long-term, collaborative solutions.

Looking ahead

Microplastics are not an isolated problem, and they will not disappear overnight. But science has already made tremendous progress in understanding their origins, where they accumulate and how they interact with ecosystems.

By combining local research with global knowledge, communities around Lake Superior can make informed decisions that safeguard water quality for future generations. The story of microplastics is not just about pollution — it’s about responsibility, resilience and our relationship with the waters that define us.

Small choices, big impact: What we can do about microplastics

Ultimately, while microplastic pollution is a global issue, meaningful change begins at the community level. Citizens have the power to influence both behavior and policy. Writing to local and state legislators, supporting science-based environmental legislation and advocating for improved waste management and stormwater systems can drive systemic change.

At the individual level, small daily choices add up: reducing single-use plastics, choosing natural over synthetic fibers, using reusable containers and being mindful of how products are disposed of can significantly reduce plastic inputs into our waterways.

Supporting businesses that prioritize sustainable practices and participating in local cleanup efforts also contribute to solutions.

Perhaps most importantly, staying informed and fostering conversations about the long-term consequences of plastic use help build a culture of environmental responsibility.

Protecting Lake Superior – and waters around the world – depends not only on scientific research but also on collective action and shared commitment.

Dr. Lorena M. Rios Mendoza is a professor in the Natural Sciences Dept. at the University of Wisconsin-Superior.