This post is the last blog of the GAME 2025 project. Unfortunately, it was delayed by several months (the project ended in December 2025), but it was not forgotten. Read now about the extraordinary and dramatic experiences that Andrea and Sarah made in Cabo Verde in 2025.
In April 2025, GAME returned once again to the islands of Cabo Verde, this time with Andrea (Technical University of the Atlantic, Cabo Verde) and Sarah (University of Potsdam, Germany). As in previous years, we were exploring the influence of artificial light at night (ALAN) on coastal organisms. The project in 2025 was supposed to bring more knowledge about its influence on the growth of marine epiphytes.
Cabo Verde comprises 10 main islands and a few islets, which are lined up in an arc in the Northern Atlantic. The archipelago was formed by underwater volcanoes that started to emerge from the depths of the ocean about 20 million years ago. The islands are characterized by a dry landscape that has arid and poorly permeable soils, which are almost infertile, and by rainfalls that do not appear every year. Hence, the inhabitants of the archipelago always found their greatest wealth in the sea. As the westernmost African country, its isolation has led to the evolution of marine species that are unique to the islands, while other species that arrived from elsewhere found favourable conditions here. As a relatively young nation, Cabo Verde has yet to explore much of its biodiversity, as well as the marine ecosystems in its waters. Partnerships between Cabo Verde and Germany, which result in projects such as the one we are participating in in the framework of GAME, are always celebrated as they contribute to the scientific enrichment of the country.
Our project was conducted in collaboration with the OSCM (Ocean Science Center Mindelo). The center is, on the one hand, linked to GEOMAR (GEOMAR Helmholtz Centre for Ocean Research Kiel) in Germany and, on the other hand, to IMar (Instituto do Mar) in Cabo Verde. It is dedicated to oceanographic observations and research, and also acts as a connection point for common research activities and the exchange between international scientific institutions. Laboratory work can, for instance, be carried out by using the center facilities and the available equipment. Our experiment, however, was conducted in the field, because of the need for a constant supply with seaweed spores that mediated the colonization of the substrates we provided by epiphytes.
To meet the specific requirements of our study, Porto Grande Bay, more specifically the Mindelo Marina, was chosen as the study site. As its name suggests, this bay is one of the largest in Cabo Verde, and it is located in the northwest of the island of São Vicente. Its calm and shallow waters made it the ideal site for the study we were planning. Except for the intense sun and very strong wind that we felt during the first months of our field work, the place was one of the most interesting and dynamic ones in Mindelo. We spent our days on pontoon B, in front of the Marina Bistro bar, working from morning to night.
In the mornings, we could smell the aroma of stewed “catchupa” and of the seafood that was served there. In the afternoons, the atmosphere was enlivened by the most famous pop songs played at the Ponte d’Água Hotel. Whenever a familiar song came on, we couldn’t resist singing along: “Kiss me hard before you go, Summertime sadness…” At dawn, everything then became calmer. The water was still, and under the lights of the pier, fish swam in circles and created a silent spectacle. Furthermore, in the months before the nesting season in Cabo Verde, it was common to see sea turtles coming to the surface to breathe. Unfortunately, they were so fast that it was almost impossible to get a photo. So fast that Sarah rarely managed to see them. If it were a game, the score would be: Cabo Verde 7 x 1 Germany.
During our work, we met people, both local and from other countries, who were friendly and willing to help, whether with a screwdriver, a tape measure, or a kayak. They were teaching us how to tie a knot, they took photos and videos of us, were giving us ideas and suggestions, or simply provided us company. However, there were also plenty of curious onlookers, mainly elderly tourists who came from the bar-bistro over to the pier, and were interested in what we were doing.
We started our work with one of the biggest challenges of the project: finding a macroalga that could be suitable for the experiment. This alga would needed to have a leathery texture, a flat and broad surface, and should inhabit the subtidal. This was no easy task for us, because although Cabo Verde has a rich marine biodiversity, the biomass of macroalgal species is limited by the nutrient deficiency in the oligotrophic waters of the archipelago. Hence, macroalgae can only be found in small quantities. Furthermore, as it is a tropical country, this task was further complicated by the fact that the waters are warm and shallow, and such conditions mainly favour encrusting and filamentous macroalgae. We began our endeavor by searching online for inventory lists of marine macroalgae on the island of São Vicente, but this was without success. We then invested in more practical approaches, such as diving and snorkeling. We went to the Laginha Coral Cove accompanied by Professor Guilherme, who is a marine biology enthusiast. There, we found two species of macroalgae, both potentially invasive and possibly belonging to the genus Grateloupia, which were qualified to serve as “living substrates” in our experiment.
We collected several specimens of the two species to hang them into the harbour in Mindelo for a pilot study. This was to test if epiphytes would settle on the macroalgae and whether the macroalgae themselves would survive the conditions in the harbour.
Both species made it into the final round. One of them had the perfect shape, but it was far too rare for our needs, while the other candidate was much more abundant. So, we focused on the second one. A further problem we faced was that the macroalgae we worked with had not been scientifically described for Cabo Verde. This meant that there was no literature that we could have consulted to learn about morphological or physiological traits. Furthermore, we had no idea how the algae would performed at different water depths or during low tide when exposed to air.
After some weeks, however, it became clear that our chosen species were rather trapping sediment on their surface than hosting a healthy community of epiphytes. Actually, even under the microscope, sediment and epiphytes were almost impossible to separate. Our supervisor, Corrine Almeida, suspected that the algae’s branched structure made it a natural sediment trap and this was not ideal for our purposes.
Given the high sediment load and the generally murky water in the harbour, we realized that we needed a new plan. We revisited the idea of using our first, more promising species, but after extensive searching, we had to admit that there simply were not enough specimens.
Due to this problem, we were unable to continue with the experiment, but the GAME programme coordinator, Mark, came up with a suggestion. The idea was to replace the living substrate with an artificial material that could, at least partly, simulate the traits of macroalgae, such as a flexible structure. Initially, we thought of using PVC tarpaulin, but this material has high chemical concentrations, which could affect the attachment of epiphytes. We continued searching in Mindelo until we finally found a silicone cooking mat in a Chinese store. The material was thin and malleable, requiring only to be soaked in drinking water for a few days to make its surface rougher. We bought eight green ones, which, after soaking, were cut into pieces that had the same size as the PVC plates.
For building the set up, we unpacked some materials that were left behind at OSCM by previous GAME teams, tested the LEDs, and cleaned the frames. One frame needed patching, while we built another one from the scratch. Mindelo does not have a giant all-in-one hardware store like the ones you can find in Germany – instead, you need to visit several smaller shops, while explaining every time at the counter what excatly you need. If they do not have it, they’ll usually send you to another store that might have it. After a few visits, the shopkeepers start to recognize you and let you rummage around in their storage rooms to find suitable alternatives.
We brought PVC panels from Germany and hand-cut them into 5 × 12 cm pieces. For the frames, we glued PVC pipes together and used thin ropes to create the inner structure. The panels were then attached to the ropes with cable ties, while the fake algae were sewed onto them with needle and thread.
We then installed the lighting system with the help of Eder, who is a technician at OSCM. All electronics were kept in waterproof dry boxes, and we built wooden arms with metal brackets to hold them in their place on the pontoon. We aimed to create similar light fields for both of our frames: Andrea’s with an intensity of 10–20 lux, while Sarah’s had 20–30 lux. After some trial and error, we managed to tune the LEDs perfectly.
However, the real challenge in June was not the construction – it was the wind. With daily gusts of 25–40 km/h, anything lightweight was instantly blown away and we are proud to say that we only lost one measuring tape to the sea. Along the way, we pulled plenty of harbour trash from the water, but also some unusual finds – like a fully inflated unicorn float. We even managed to recover the lid of our dry box from the seafloor, along with a couple of our caps. Hats, in fact, did not stand a chance in the winds of June and keeping them on our heads required constant hand support, so we eventually gave up.
By early July, just in time for our first experiment, the weather turned calmer. This made deploying the frames with our kayak much easier. Earlier, any pause in paddling would have sent us drifting straight back to the pontoon. The kayak also came in handy for measuring the water depth at the experimental site and for adjusting our mooring lines.
In this moment, we were optimistic: The project was starting to get on track. It seemed that we could finally switch on the autopilot and continue the work as outlined in the GAME 2025 manual. However, first we had to test the different steps of the analytical processes in the laboratory. We collected some of the fake algae that we had placed on the frames as backups in case of losses, put them in freezer bags and packed the freezer bags in larger black bags that we filled with ice and transported them to the laboratory. The first step, i.e. scraping the epiphytes from the substrates, went well, but a problem emerged when we tried to perform vacuum filtration. For this, the suspension of seawater, epiphytes, and sediment was poured into the funnel of the filtration unit, and the device was turned on. After a considerable amount of time, we could see that the volume in the funnel had not changed, because the sediment had clogged the flow of water through the filter. We were once again faced with a new impasse, and this one required a solution within a week. This was because the first experiment had already been running for more than seven days and could only continue for one more week. We tried decanting, but the epiphytes and sediment settled at a similar rate at the bottom of the beaker, making it difficult to separate them. Then we tried sieving through different sized meshes, but in doing so we lost a lot of biomass, what would have compromised our results. We also tried a method involving aliquots, which could have worked, but it took too long to test it a second time.
With no time left, we decided to remove the filtration step and to leave the sediment in our samples, as we simply could not get rid of it. Hence, the freezer bags were already drained at the study site. In the laboratory, the epiphytes were scraped off and directly transferred to test tubes, which were then filled up with ethanol. This method proved to be successful as we obtained chlorophyll a concentrations that were similar to those of the other GAME teams. For the biomass samples, a similar method was used, but their processing required the use of a muffle oven to obtain the ash-free dry weight. As none of the institutions here in Mindelo have such equipment, the samples were transported to Germany to muffle them at GEOMAR.
At this point, we were already thinking about what aspects could be improved in our second experiment, which was already underway. Furthermore, Sarah recently completed her first dive, spotting a nurse shark, plenty of fish, and sea turtles. She was hoping to spend more evenings at the beach in the coming weeks, playing volleyball and enjoying live music, especially during the Baía das Gatas Festival—one of the largest festivals in the country—which was approaching. In the words of our advisor, “The project is now running smoothly.” However, no one expected that in August a country that rarely receives rain throughout the year would be shaken by the biggest storm in living memory.
In the early hours of August 11th, storm Erin arrived without warning, causing material losses and, sadly, claiming the lives of nine people on the island of São Vicente. During the night, the scene was one of horror, with streets turned into rivers, lightning illuminating the entire city, and people desperately fighting for their lives and those of their loved ones as rainwater flooded their homes. In the morning, it was then possible to get a real sense of what had happened. Buildings had been knocked down, cars carried out to sea, shops destroyed, all caused by the force of the rainwater. The Mindelo micro-watershed, characterized by a mountainous terrain and a rugged topography, allowed the rainwater that fell on the city to flush to Porto Grande Bay, resulting in an exacerbated discharge of muddy water accompanied by trash. Experiment 2, which had already been in the water for a week, was canceled as the conditions in the bay no longer met the requirements for conducting an experiment. Square kilometers of water that had been crystal clear had turned brown and opaque, and we had no idea how long these conditions would last.
Soon after the storm, it was decided that the team would split up: Sarah would go to Finland to continue her project with the GAME team there, and Andrea would stay here to continue as soon as conditions had improved. A month passed, and the bay was slowly returning to its normal colour, but then another rain came and turned it brown again. Then it was too late to repeat experiment 2. But all is not lost. In January 2026, after we had completed the last phase of the project at GEOMAR in Kiel, Andrea considered to continue with the experimental work. At this time, the rainy season in Cabo Verde was over, and the water was still at mild temperatures.
The unforgettable catastrophe of August 11th 2025 in São Vicente allowed us to speculate on the origin of the mud/sediment that affected our experiment. The sediment that accumulated on the substrates probably came from the muddy water that floods Porto Grande Bay every year during the rainy season. Somehow—possibly due to the regular entry and exit of ferries from the port—the sediment gets resuspended frequently and travels through the water column by the forces of tidal currents and others. At least one riddle was solved.
Ocean Acidification
Barnacles, buoys and boat engines: researching the effects of underwater sound in Malaysia
Selamat Datang and welcome to the hot and sweaty country of Malaysia! Ever since we, Leonie and Najwa, have arrived in Penang, the northwestern island of Malaysia, in April this year, it has been a constant 30 degrees with an average humidity of 70%. However, it feels both hotter and more humid than that. Unfortunately, the weather will not change much during our stay as Malaysia lies very close to the equator (at latitude 5°N). Thus, it has no seasons, but a nearly constant temperature and day/night rhythm of 12 hours.
Beginning to adapt
The sun is just peaking above the sea when I (Leonie) have to leave my house. The bus leaves (more or less) always at the perfect time to watch the sun slowly rise over the ocean. I use the 30 min bus ride, which costs me about 2 Ringitt (or ~20 cent), to wake up and prepare for the day ahead at the Centre for Marine and Coastal Studies (CEMACS). During the bus ride beaches, restaurants, cafés and small towns pass by in the window. Especially, one secluded beach and its beach house, which is for sale, make the bus ride go by fast – thanks to daydreaming about living there. When I arrives at 8 am at the entrance to the National park, in which the institute is located, Najwa is already waiting for me. She only needs a 5 minute car ride to get there from home, since she found an apartment close by. Now we just have to wait for the boat to take us to the institute within the national park. Technically, a 40 min hike through the park would also do the trick, but both of us are not ready for such a sporty activity at 8 in the morning and a daily boat ride is so much more fun anyways.
CEMACS lies in the heart of the Taman Negara Pulau Pinang, the national park of the island of Penang in northwestern Malaysia. Because of that, it’s quite a way to the big city of Georgetown and thus sources of noise, disturbances and pollution are far away. This is especially important for this year’s GAME project as we aim to find out whether underwater soundscapes influence the formation of hard-bottom communities.
The sunset by the institute (right, © Leonie).
We are trying to find answers to this question in the warm and salty ocean right in front of the gates of CEMACS. For that we deploy large metal frames that carry settlement panels into the sea. Two of those frames will additionally be equipped with an underwater speaker with which we can playback – in principle – any kind of sound we like (trust me, it was tested and it was a good day). To distinguish between the experiments that the two of us will conduct, we will use different soundscapes. One will focus on anthropogenic noise, i.e. the sound that is emitted by either a fishing or a container vessel. The noise will be played back at random times during the day, but will accumulate to a total of 30 minutes every hour. The other team member will focus on a natural soundscape that will be recorded at a healthy underwater location close by. The settlement panels will be retrieved regularly in order to find out how and if the playbacks are affecting the composition of the establishing hard-bottom communities.
Sounds easy enough, yea? Technically it is, but the nature can be treacherous around here. Jellyfish, like the Ribbon Jellyfish (Chrysaora chinensis), are daily visitors and as pretty as they are, as much does it hurt to get stung by them. After some painful incidents, we now wear full body coverage whenever we are in the water to minimize the skin contact. One person, who stands on land, is always watching the water surface to give a warning in case one of us comes too close to one of the jellies. It’s important to always have someone watching, since we don’t see a lot when we are in the water ourselves. The visibility can be so poor that you cannot even see your hand in front of you. Which is why we struggle to detect the up to 50 cm long tentacles that can sting us. The jellies drift with the currents and like to hang around the jetty, where our frames are deployed.
But even on the land, it’s not entirely safe. Since CEMACS is in the middle of the national park, it is not uncommon to see animals around the institute. The cats and even the lizards are rather cute to look at but the monkeys and the mosquitos? A nightmare! Before the morning boat even leaves at 08:10 both of us already have 5 mosquito bites, a constant buzzing in the ear and are always itchy. Want to have your lunch by the water on the beach? Think twice because monkeys can and will steal your food. Even the laboratory is not safe and has to be locked up monkey-proof.
When we are not blasting ABBA or LinkinPark while setting-up our experiment or trying not to get stung by jellyfish during maintenance work in the water, we can actually enjoy Georgetown. The city is about 1 hour by bus from our living quarters and offers the exact opposite of CEMACS. It is loud, full, bright and brimming with life (humans, not animals). Due to its rich mix of Malay, Chinese, Indian and indigenous cultures clashing together, you can find every kind of food downtown. From delicious savoury food over sticky fruits and drinks to sweet desserts. You can find these tasty items all over the island often in hawker stalls or cute restaurants. Of course, you can also go shopping wonderfully (much to the dismay of Leonie and her limited baggage weight for the flight back home) or just walk around the town and get swept up by the street murals, salty breeze and picturesque buildings.
Do we have to restart?
The deployment of our frames went smoothly, attaching and retrieving the HydroMoths (i.e. hydrophones) went smoothly, and the preparation for the sampling week went smoothly. Probably, everything went a bit too smooth in hindsight, because when the sampling week arrived, nothing went smoothly.
We seemingly lost our entire control frame (i.e. frame without sound playbacks).
During our daily boat ride towards CEMACS we have normally perfect view to see the white buoys of our control frame floating in the distance. Except on that Tuesday. The weather was a bit rough over the weekend and it was still windy and wavy, so we tried to argue that the glare of the sun plus the waves are messing with our eyesight. Surely, we would see it once we get out there to take off and analyse our panels. But when our boat reached the exact coordinates, at which we deployed the frame, there was nothing. No buoy. No rope. No frame. No hint whatsoever. Immediately, we got into the water and were searching the area with the help of two colleagues. But still, we found nothing. The visibility was not in our favour and Najwa got stung by a jelly, what didn’t make the situation better.
After we had to realize that the possibilities were high that our frame got either stolen by someone or it got washed away during the storms, we accepted defeat. Over the next couple of days, we were analysing the panels from the frame with sound playback (aka speaker frame) and discussed options with our supervisors. Upon agreement we started one more search and rescue mission. This time we were dragging an anchor across the seabed for quite some time. Clammy hands, shallow breath and elevated heartbeat. Everyone on the boat was on edge after 30 min of searching. Our colleague held up his hand. The boat stopped. He got something. To everybody’s surprise he pulled up our control frame!! It was completely covered with barnacles, so that the frames and panels were barely distinguishable but we got it back. It obviously became to heavy for the buouys that we attached to it and sank to the seafloor. Immediately, we got to work: Pulling the frame onto the boat, cutting off each panel to inspect it in the lab and cleaning the frame (which was equally stinky, disgusting and difficult).
Now the hard work began: analysing the panels. We first weighed and photographed them to estimate the biomass and the degree of coverage on them. Then each and every panel needed to be inspected through a stereomicroscope to identify as many organisms as possible. Most of the panels were covered with barnacles, to be precise it was Amphibalanus amphritite. But apart from that we also found some worms that built themselves tubes on our panels (probably individuals from the family Sepulidae and Spionidae) and were thus sessile too, some bryozoans, colourful tunicates and a lot of small shrimps, crabs and flatworms that were roaming around. Just within four weeks, the sad-looking grey PVC panels have become a location for the smaller animals of the ocean to settle and start their lives.
Before we deployed the frame again, we attached a total of 13 buoys and have now a little buoy party in the water which never fails to make us giggle. They are supposed to prevent the frame from sinking again.
The natural soundscape dilemma
Now that Leonies experiment is running (more or less smoothly) it is time to concentrate on the preparation for Najwas experiment which will focus on the natural soundscape.
At first, CEMACS and Penang seemed like the perfect place to begin collecting natural soundscape recordings. We believed it would provide a healthy, natural, and undisturbed underwater acoustic environment. However, despite being located in the national park with little human activity per se, Penang is one of Malaysia’s busiest coastal regions. The constant movement of ferries, fishing boats, tourist vessels, and commercial shipping creates a persistent layer of anthropogenic noise beneath the water. Instead of capturing the quiet rhythms of marine life, many of the recordings that we made were dominated by human activity. It became clear that Penang was not the ideal location for getting an undisturbed soundscape on tape. But where can we find that?
The search led us to Langkawi, an archipelago of 99 islands located just 100 km north of Penang near the border with Thailand. Renowned for its clear waters, rich marine biodiversity, and relatively low levels of coastal development in certain areas, Langkawi offered a far more promising environment for natural underwater acoustic recordings.
Within Langkawi, our attention turned to Pulau Anak Datai, a small island situated off the northwestern coast of the main Langkawi Island. It’s surrounded by coral reefs, rocky shorelines, and lush tropical rainforest. Compared to many of the more popular tourist destinations in Langkawi, Pulau Anak Datai experiences considerably less boat traffic, allowing its underwater environment to retain a more natural acoustic character. These conditions make it an ideal site for our needs.
With the study site finally selected, the next challenge was deploying the HydroMoths.
The recordings were scheduled over five consecutive days, with two HydroMoths deployed simultaneously to maximize the number of sites we could survey. To secure the HydroMoths underwater, we brought along two concrete blocks fitted with metal poles from CEMACS. These were previously used by another GAME team, and at the time, they seemed like the perfect solution. The concrete blocks were heavy, stable, and, most importantly, gave us peace of mind. We were worried about the HydroMoths moving with waves and currents, creating unwanted handling noise in the recordings. We were also concerned about the possibility of losing the devices whether due to storms, strong currents, or even someone discovering and taking them. But due to the seabed at Pulau Anak Datai being covered in rocks, corals and just life, it was difficult to position the blocks securely. The handling became a struggle, above and underwater.
No, we needed to adapt. Field work has a funny way of destroying the illusion of a thought through plan and pointing out every little flaw. We thought the original plan was fool proof. Turns out, it was not.
After surveying the area more closely and brainstorming some ideas, we purchased ~100 cm long metal poles, which we would simply hammer down into the ground between the corals. We then could attach the HydroMoths onto them. Fool proof, for real.
The new setup was lighter, easier to transport, quicker to deploy, and required only a fraction of the energy needed for the concrete blocks. What initially felt like a major setback showed us that flexibility and adaptability are the most important qualities during field work. And keeping a cool head, which can be the most difficult part.
Najwa is now owner of hours on end of the natural underwater soundscape in Langkawi. In order to actually use it as a playback, though, she has to listen, filter, crop and edit the recordings.
Every obstacle from searching for a truly natural soundscape to redesigning our deployment method became a lesson that no classroom could have taught. In the midst of our experiment, we are still learning to adapt, be patient with ourselves and stay curious about the processes and solutions that fieldwork demand. The ocean rarely follows our plans, but perhaps that is exactly what makes studying it so rewarding. Jumpa lagi! (See y’all!)
Barnacles, buoys and boat engines: researching the effects of underwater sound in Malaysia
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
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.
Driving a car or even riding in a bus is a bit like dragging an eraser across the planet, except the crumbs are microplastics. Toxic microplastics.
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.
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.
Give today and make a difference!
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.
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