When moon jellyfish gather in large numbers, the bloom is impossible to ignore. Hundreds or thousands of medusae can suddenly fill a bay or fjord. Because this swimming stage is so visible, it is often the focus of monitoring and research. But the familiar jellyfish is only one chapter in a much more complex life cycle. Before entering the open water, moon jellyfish can spend years as tiny polyps attached to rocks, algae or other hard surfaces on the seafloor. These polyps reproduce asexually and release young jellyfish when conditions are suitable. Our new study in Trondheimsfjorden, Norway, shows why this hidden stage deserves much more attention. The central finding is that the stage that moves the least may be the stage that gives a jellyfish population its greatest stability.

Image courtesy: https://sciencedigest.org/facts-about-jellyfish/

One animal two worlds

Moon jellyfish (Aurelia aurita) alternate between two contrasting habitats. Polyps remain attached to the seabed and can persist locally for years. Medusae live in the water column for a much shorter time and can be transported by currents across the fjord.

This creates an ecological puzzle. If medusae can travel widely, should populations throughout a fjord become genetically well mixed? Or can local structure survive because the stationary polyp stage retains diversity in particular places? Our new study in Trondheimsfjorden, Norway, shows that these hidden polyps may be crucial for maintaining genetic diversity. We combined field observations, genetic analyses of 572 samples and a model of movement through fjord currents. We found 70 genetic variants—and a striking difference between life stages.Polyps consistently held high genetic diversity. Medusae varied much more between places and years and were sometimes dominated by only a few variants. The polyps therefore appear to act like a biological seed bank: many possibilities remain stored out of sight, while each year’s conditions determine which ones emerge.

Currents alone could not explain the genetic patterns: the model predicted more mixing than was observed among medusae. Transport is therefore only part of the story. Local retention, temperature, food, survival and reproductive timing can filter which variants reach the visible stage.

This matters because jellyfish blooms affect food webs, fisheries, tourism and coastal infrastructure. Better forecasts will require more than counting medusae or following currents. We must also monitor polyp habitats and understand what controls transitions between life stages.

The wider lesson is simple: to understand the connectivity and resilience of marine organisms, we cannot study only the most visible, or most mobile part of their lives.

Paper: Majaneva, S., Ellingsen, I., Javidpour, J. and Aberle, N. (2026). Benthic life stages retain fjord-scale population structure despite pelagic dispersal. Frontiers in Marine Science, 13:1895768. https://doi.org/10.3389/fmars.2026.1895768

The jellyfish we see are only half the story

What do you think about when you hear the words “microplastic pollution?” Your mind may immediately go to imagery of colorful fragmented plastics broken off from bottles, buckets and other items we use in our everyday lives. Or, perhaps, you imagine a pile of microplastic fibers—the tiny, squiggly, spaghetti-shaped plastics that shed from our synthetic clothing. You may be surprised to hear there is another major source of microplastic pollution that’s hiding in plain sight, quite literally under our feet, that might change how you think about microplastics: tire particles.

We all know tires wear down over time—that’s why we have to replace them on our cars roughly every 60,000 miles or so. Every time a vehicle accelerates, brakes or simply drives down the road, the friction between its tires and the pavement creates tiny fragments of rubber, known as tire wear particles.

Tires are made from a complex mix of natural and synthetic rubber along with a range of additives, fillers and chemical compounds—some of which, like the preservative 6PPD, have been shown to be highly toxic to coho salmon when they break down into derivative product 6PPD-Q in the environment—even in tiny concentrations.

Some studies have shown that a single vehicle’s tires can emit more than two trillion particles per mile driven—and that the average person generates nearly two pounds of tire particles per year! Once these particles are shed from tires, they don’t just disappear. Some are small and light enough to become airborne, drifting away from roadways as dust. Others settle on road surfaces, where they accumulate until the next heavy rain washes them into storm drains and from there, into streams, rivers and eventually the ocean.

That’s why tire wear particles are now considered one of the top sources of microplastics to the environment. In fact, until recent developments in analytical methods, scientists weren’t reliably able to detect tire wear particles in microplastic counts—thus, these pesky microplastics may have been evading our detection for years.

Why green infrastructure may be one of our best near-term solutions

Unlike some sources of plastic pollution, we can’t simply stop driving overnight. Reformulating tire rubber to be less toxic or shed less material, while promising, will take time to develop, test and scale across the global vehicle fleet. So, what can we do about tire wear particle pollution right now?

This is where green infrastructure comes in. Green infrastructure refers to engineered natural systems (things like bioswales, rain gardens, roadside buffers and permeable pavement) that are designed to slow down, filter and treat stormwater before it reaches rivers, lakes and coastlines. Instead of routing runoff directly into storm drains and out to sea, green infrastructure gives contaminated water a chance to percolate through soil, plants and other natural filtration media, which helps trap microplastics, including tire wear particles, preventing them moving further downstream.

Early research on green infrastructure has been promising, showing that these systems are quite effective at capturing microplastics and other contaminants carried in road runoff. But there’s a critical piece we still don’t fully understand: What would it take to scale up green infrastructure across an entire city, and how much of a dent would that actually make in long-term tire wear particle pollution?

Our research on green infrastructure capture of tire wear particles

Funded by the Tire Industry Project, our plastics science and policy teams at Ocean Conservancy have partnered with the University of Toronto on a new study evaluating the costs and benefits of scaling up green infrastructure at the city level specifically to capture tire wear particles.

If you happen to be driving on the roadways of Portland, Oregon, you may spot our scientists crouched over, precariously scooping dirt with spoons from a sample area on the roadside. Don’t be alarmed—that’s just us doing science! Feel free to give us a wave.

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Ocean Conservancy is currently working to:

• Quantify the scale of pollution: Collect road dust samples from 30 cities globally to measure both total microplastic and tire wear particle concentrations and determine how different variables (population density, road size, rainfall) might influence those values.
• Assess feasibility: Determine what it would take realistically—logistically, financially and spatially—to scale up green infrastructure across an entire city.
• Model positive impacts: Estimate how much city-scale green infrastructure could reduce tire wear particle pollution entering aquatic ecosystems.
• Compare across cities: Understand how well these solutions might translate across different urban contexts, focusing on Portland, Oregon; Toronto, Canada; and London, England as case-study cities.
• Make our findings accessible: Produce a public-facing toolkit to help city planners, engineers and advocates guide real-world implementation of infrastructure that captures tire-wire particles. 

By pairing rigorous science with practical guidance, we hope to help cities move from asking “Could this work?” to confidently building solutions that we know can be effective.

How can I help?

Tire wear particle pollution can feel like an overwhelming problem. After all, it’s tied to transportation, which most of us rely on every day. But that’s exactly why research like this matters: It gives us a real, near-term path forward that doesn’t require waiting for the entire global transportation system to change first.

You can help by staying engaged with Ocean Conservancy as we continue to dig into solutions for the plastic pollution crisis—one roadway, one storm drain and one city at a time. Together, we can keep working toward a world and ocean free of plastic pollution, forever and for everyone.

The post What are Tire Wear Particles? appeared first on Ocean Conservancy.

What are Tire Wear Particles?

A small jellyfish-like animal recently reported from Vejle Fjord has attracted attention. Clear photographs suggest that it belongs to the genus Gonionemus and may possibly be the clinging jellyfish, Gonionemus vertens (Picture courtesy to Jonas Bøgelund Poulsen)

Unlike the large jellyfish commonly encountered along Danish coasts, Gonionemus vertens is a small hydromedusa, usually only around 1.5–2.5 centimetres across. Its transparent bell reveals four coloured reproductive structures arranged like a cross. Numerous fine tentacles surround the bell, often appearing bent or angled. Small adhesive pads near the ends of the tentacles allow the animal to attach itself to eelgrass, seaweed and other submerged vegetation.

This unusual behaviour explains its English name: the clinging jellyfish. During the day, it often remains attached to vegetation rather than drifting freely with the current. At night, it becomes more active and swims into the water column to feed on zooplankton and small crustaceans. Consequently, it can easily remain unnoticed even in places where it is already established. Another reason the species can be difficult to detect is its life cycle. The visible medusa is only one stage. For much of its life, the animal may persist as a minute polyp attached to a hard surface, shell or vegetation. These inconspicuous polyps can reproduce asexually and later release new medusae when environmental conditions become favourable.

Gonionemus vertens is generally considered native to the northern Pacific but has been introduced into several parts of Europe and the Atlantic. Transport on ship hulls, in ballast water or with movements of oysters and other marine organisms has been suggested as possible pathways, although the pathway responsible for any particular occurrence is rarely known with certainty.

Despite its delicate appearance, the animal should not be touched. Some populations possess powerful stinging cells and have caused intense pain, swelling, muscle cramps and, in rare cases, serious allergic reactions. Sting severity differs considerably among regions, which is one reason researchers suspect that animals currently grouped under the name G. vertens may represent a complex of closely related forms.

The Vejle Fjord observation is therefore scientifically interesting, but it should not yet be presented as a confirmed record of G. vertens. Anyone encountering a similar animal should photograph it without handling it and record the date, exact location, approximate size, number observed and surrounding habitat. Observations can be submitted to Denmark’s national species portal, Arter, where they can be evaluated and contribute to tracking changes in Danish marine biodiversity. Please use either my App: GoJelly JellySpotter or reprot to the Arter.dk: Gonionemus taxon page and Danish species-reporting portal.

References:

Edwards, C. (1977). A study in erratic distribution: The occurrence of the medusa Gonionemus in relation to the distribution of oysters. Advances in Marine Biology, 14, 251–284. DOI: 10.1016/S0065-2881(08)60448-4.
Govindarajan, A. F., Källström, B., Selander, E., Östman, C., & Dahlgren, T. G. (2019). The highly toxic and cryptogenic clinging jellyfish Gonionemus sp. (Hydrozoa, Limnomedusae) on the Swedish west coast. PeerJ, 7, e6883. DOI: 10.7717/peerj.6883.

A tiny but remarkable visitor in Vejle Fjord-Denmark?