Wild Atlantic salmon are opportunistic carnivores, with a broad menu that includes small fish and crustaceans. Farmed salmon are fed nutrient-dense pellets that are carefully formulated to maximise growth. The list of ingredients includes soy protein, vegetable oils, fish oils and fish meal. Yet while the salmon may struggle with digesting their peculiar processed diet, the main environmental peril is the free-flow design of the pens.
Sunstone Institute research reveals that less than half of the nutrients fed to the salmon are absorbed and help the fish to grow. The other generous half is excreted as faeces and urine, or remains uneaten.
Mixed together, this waste rains down through open pens into the surrounding water. The result is a rich nutrient soup of dissolved nitrogen, phosphorus and organic carbon.
Other human sources of nutrients pollute Norwegian coastal waters - agricultural run-off, municipal wastewater and sewage, industry and run-off from built-up areas - but from the southern tip of Norway and all along the coast up north, aquaculture is the single largest source.
In line with the colossal spread of salmon farms, the amount of waste entering Norway’s fjords and coastal waters has been rising, year on year. Sunstone Institute research reveals that, reaching a pinnacle in 2025, the nitrogen and phosphorus in this waste were equivalent to the raw sewage from 17.2 million and 20 million people, respectively. That’s more than three times the population of Norway. Triple the toilet waste from an entire country.
More unsettling is the figure for organic carbon. Imagine the entire population of Australia (29.6 million people) relieving themselves directly into Norwegian fjords. That’s the scale we’re dealing with.
“The discharge of nutrients and organic matter from aquaculture can be significant when expressed as population equivalents, but such conversions must be interpreted carefully”, writes State Secretary to Minister of Climate and Environment, Kristoffer André Hansen, in an e-mail to Sunstone when presented with our findings. The environmental impact depends on local conditions and the ecosystem’s capacity to absorb them, he says, but admits they can harm vulnerable fjords and coastal areas.
So what’s the problem with all these extra nutrients swilling around the coast? Nutrients help things to grow, isn’t that good? Unfortunately not.
Return to Herand
A year after he was there investigating with his underwater drone, Nordahl is back in the Hardangerfjord and joined by Hartvig Christie, pioneering marine scientist at Norwegian Institute for Water Research (NIVA). Christie has dedicated his whole life to kelp ecosystems and has shaped our understanding of these underwater forests. At the age of 76 he is still diving.
It is August, 2025. The plan is to take their boat and freedive around the islands of Storeklubbena and Herandsholmen, west of Herand.
They aim to document how the kelp forest looks in the light of its proximity to both the salmon hatchery and several open-net sea farms in the fjord. Not far from where they plan to dive, the fjord plunges to depths of more than 800 metres, providing a generous sweep of water to dilute waste from the salmon facilities.
Setting off from the launch site near Herand, they arrive at the islands and anchor the boat in a sheltered bay. Pulling on their dive gear, they flop over the side and swim out along the rocks.
Near the surface, signs are encouraging. The gardens of shallow water seaweeds are thick and healthy.
But as they descend just a few metres, the scene takes on a shabbiness typical of a suffocating algae; lurv.
These algae bloom when nutrient levels are high, smothering other marine life, and when they die in autumn and sink to deep water to rot, they deplete the seabed of oxygen.
Swimming on with a growing unease, they reach deeper water where kelp grows. Below them, the canopy of golden fronds looks strange. Inhaling deeply, they dive down to investigate. Looming into view is a woolly layer of lurv blanketing the kelp.
Rising and bobbing back to the surface, Christie and Nordahl exchange exasperated head shakes, their shared fear coming to fruition. Another spot is added to the map of kelp forests struggling under the load of excess nutrients.
They dive back down. Between the two islands, lurv has established itself on the rock walls too, draped like rugs over dishevelled-looking kelp. But on the outside of the islands, the walls are strangely bare. Looking closer, Nordahl spots them. Armies of white sea urchins among the sand and rock on the seabed.
Usually, they are restricted to deeper waters. Yet here, instead of a diverse mosaic of marine life, the surroundings are scoured clean by their grazing. As Nordahl descends the wall to 18 metres, he catches up with another swathe of urchins. Full, they are returning to the depths.
What nutrients do in the sea
Three nutrients are fundamental to how ecosystems grow and function: nitrogen, phosphorus, and carbon. In the sea, nitrogen and phosphorus act as fertilisers but are naturally scarce and are the limiting nutrients that keep algal growth in check.
When nitrogen and phosphorus loads in the water increase, they trigger blooms of rapid algal growth. As the algae die, their decay depletes the surrounding water of oxygen. This is called eutrophication and it is a global problem.
An excess of organic carbon provides a feast for oxygen-hungry bacteria which compounds the problem further.
Salmon farms release nitrogen, phosphorus and organic carbon continuously and largely uncontrolled, with levels increasing every year. In the summer, salmon are fed more than twice as much as they are in the winter, creating a massive surge of nutrient waste in warming waters—exactly when lurv thrives.
Scientists have suspected for years that salmon farm waste harms Norway’s kelp forests, yet few studies have addressed the link. The expansion of the industry from small farms in sheltered fjords to larger farms in open, coastal locations where kelp forests thrive prompted a study in 2015 by NIVA and Institute of Marine Research (IMR). Overall, the scientists found less biodiversity and more lurv in kelp forests at sites with bigger farms and higher waste levels.
This was in August 2015. Since this study, the number of commercial licenses has grown, and annual averages of both nitrogen and phosphorus in salmon farm waste have risen by more than a third. A recent report from Havforskningsinstiuttet (Norway’s Institute of Marine Research) found that Norwegian fjords and coastal systems are increasingly vulnerable due to climate change, which reduces their ability to tolerate pollution from fish farming.
In recent years, Nordahl and Christie have documented scenes of lurv proliferation in fjords and on the open coast that span a geographical sweep of around a thousand miles, from the south-west of Norway, all the way up to just north of Lofoten.
Another creature greeting Nordahl and Christie along the coast, is the red sea urchin. The explosion in their growth becomes apparent on a dive close to a hatchery in the Lofoten islands on Norway’s northwest coast.
In contrast to its white relatives, red sea urchins (Echinus esculentus) naturally belong among the kelp. But not in these numbers: From the surface to a depth of six metres, they cover the seabed in their thousands.
Ranging from walnut to grapefruit in size, generations of urchins crowd bare rock where kelp might normally grow, amidst a slow rain of waste water spewing from the pipe.
“I’ve never seen this species in such high densities before”, Christie said. “When we snorkel at other sites in Lofoten we see maybe one per square metre”.
When contacted for comment, Ellingsen Seafood referred Sunstone to independent environmental surveys taken outside of their Lofoten facility, where these videos were filmed. A representative noted that the latest of these standardized surveys, or “MOM” tests, categorised the surrounding oceans into the “best” condition class. They did not specify when these tests were last taken.
The role of the red sea urchin is to graze on the kelp forest understory of animals and plants, maintaining biodiversity as a natural part of a balanced system. But here, like the white urchins, they are feeding on waste from the pipes.
These booming resources supercharge sea urchin reproduction. Collectively, they produce millions of swimming larvae that are swept off to fresh pastures. Here, they settle on the seabed and transform to begin their adult lives as spiny munching machines. They devour kelp forests and seaweed gardens and make barrens of the seabed.
This is a tragedy not only for biodiversity but for us too. The kelp plays the same vital role in the ocean that forests do on land. They absorb carbon dioxide and release oxygen through photosynthesis, forming the foundation of the marine food web. They stabilise our climate by capturing and storing vast amounts of carbon, furnish us with food, resources and livelihoods, protect our coastlines from flooding and erosion, and nourish our mental well-being. Seaweed forests are essential to life on Earth.
Fish feed frenzy
Continuing his summer tour, Nordahl witnesses the feed station effect first hand on another dive at a Mowi-owned hatchery pipe near Imarsundet, not far from Kristiansund on the west coast. This area is famed for clipfish, a traditional method for preserving cod, haddock and saithe of salting, drying and pressing.
Accompanied by spearfishing friends, Nordahl enters the water and notices the surface is slick with slime, oil, and fish faeces. As they swim for deeper water, strings of waste sludge snag on their dive masks and drape across their lips. The potent fishy odour fills their snorkels so that as they breathe in, they taste it too.
Below them is the source: a snowstorm of waste billows from the pipe's mouth. Circling it is a huge shoal of saithe and among them, cod. Usually wary of humans, these ones are sluggish with bulging bellies and little fear.
As part of their investigation, the spearfishers shoot one saithe, one medium-sized cod and one large cod of more than 20 kg. Cutting open the saithe, a shower of half-digested pellets sprays from the stomach; the same spills from the belly of the medium cod. Finally, a large cod is speared, an easy shot today. As they slit it open, they notice the liver is enlarged and fatty, and from the stomach they pull the remains of a saithe. This cod, at least, was feasting on natural prey. But his saithe dinner is full of pellets too.
In a statement, Mowi said it was investigating the issues raised in our report, and that it complies with national emissions requirements.
Sunstone calculations show that the waste of uneaten feed from salmon farms added up to 63,871 tonnes in 2025.
Picture 4,500 commercial dump trucks backing up to the water’s edge and emptying their load of salmon feed directly into the fjords, one after another, year after year.
This provides plentiful opportunistic feasting for marine wildlife.
But at what cost to their health, and value as wild, commercial species?
The regulatory gap
How exactly is the salmon farm industry monitored, and who is responsible for regulating waste discharge from salmon production facilities? The answer is not straightforward.
Regulation is the responsibility of two different ministries with opposing goals. The Ministry of Trade and Industry prioritises growth and controls licensing according to their traffic light system of sea lice impacts on wild fish, a parasite that kills salmon. The Ministry of Climate and Environment’s primary focus is on regulating pollution. Each operates largely in isolation, creating a system where expansion licenses are granted based on narrow metrics like sea lice, while the discharge of waste often gets overlooked.
Tom N. Pedersen has worked with governance of the Norwegian salmon industry on and off since the 1980s. He is a senior advisor to the county governor of Vestland. When asked how waste outputs from fish farms are monitored and managed, Pedersen explains, “Monitoring of discharges from aquaculture facilities, both sea-based and land-based, is carried out by surveying local impacts to the seabed only. What happens elsewhere in the fjord has in general not been measured.”
He describes his experiences as an example of the boiling frog syndrome, where regulation is based on narrow, local surveys and the wider context is overlooked.
“The challenge is that the industry has grown so fast that the regulatory bodies are struggling to keep up. This shows the necessity of large scale and long term environmental monitoring”.
In a damning audit of land facilities in 2025, the Environment Agency found that nine out of ten violated pollution regulations. Just weeks before, the government released a new White Paper proposing a complete overhaul of the framework monitoring open-net sea farms. At the core was a commitment to move the entire industry toward standardised national regulations based on actual environmental impact. Yet it remains to be seen how and when these rules will be enforced.
“Only in recent years have we obtained monitoring data showing what happens across entire fjords. Discharges from aquaculture are not just about quantities but also about where they end up”, says Pedersen. “Pollution is defined as too much of something in the wrong place at the wrong time”.
The route to change lies with the licensing authority and a preemptive approach from the government, according to Pedersen. “County governors have the power to pull the brake”, he says.
They have recently done so in Hardangerfjord.
The oxygen crisis
It started when scientists wanted to find out how the amount of life-giving oxygen in the Norwegian fjords water has changed over time. For the Hardangerfjord, the County Governor searched all available archives for older hydrographic data in order to expand the ongoing monitoring programme. The result was a time series stretching back to 1955.
The study produced a graph with a profile that looked like a slide in a children's playground. This slide would be particularly thrilling to ride due to its angle. As you gather momentum through the 1970s, 80s and 90s, oxygen levels plummet. By the time you reach the present day, you’d be gasping for air.
“When I saw that graph, I was shocked”, says Tom N. Pedersen. It showed a one-third decrease in oxygen levels in the deeper parts of the fjord between 1955 and 2024. They now have two more years of monitoring showing the same trends.
The Hardangerfjord is Norway’s second longest fjord system, and is the region in Norway with the highest density of salmon farms.
The changes are also connected to climate change, whereby water exchange in fjord basins is weakened. When this coincides with increased discharges of nutrients from salmon farms, there is a clear correlation with reduced oxygen saturation in deeper water layers.
The Gjeravågen facility maintains that it complies with all Norwegian regulations.
On 26th March 2026, the County Governor of Vestland announced they were implementing a strict halt on aquaculture expansion to protect the fjord.
“Here in Vestland, we are currently at a crossroads. Recent data confirms how drastically the ecosystem has declined since the first hydrographic measurements began in the 1950s“, Pedersen explains. “In order to save the fjord all pending applications for increased production or new aquaculture sites will be rejected.”
This represents unequivocal emergency action taken in grave circumstances.
"Where evidence shows a need, particularly in vulnerable fjords, more targeted monitoring may be required", admits State Secretary to the Minister of Climate and Environment, Kristoffer André Hansen. “The government’s goal of further growth in aquaculture cannot come at the expense of fjord and coastal ecosystems”, he says.
"Four hundred million salmon in farms each year are bound to affect how the whole ecosystem functions,” Pedersen warns.
Nordahl and Christie dive together in the neighbouring Sognefjorden,
the deepest in Norway.
The lurv is prolific here too, completely covering the tangle kelp forest where they dive.
The collapse of the reference site
There are hallowed places in Norway that were thought too wild, too tide swept, too resilient to be tainted by the salmon industry, and bothered by sea urchins and lurv. In the far west of Norway, lie the islands of Finnøy, Kvaløy, Seterøya. On the seaward side of these lies the celebrated Purkeskjæret.
For decades, this small island has resisted urchin grazing, heatwaves and overgrowth by lurv, a pristine, primaeval forest at the edge of the sea. It is as lush and biodiverse as any rainforest on the land. For marine scientists like Hartvig Christie, it is an important reference site for kelp research. Their studies have gathered historical data spanning 25 years, providing a reference point, a baseline, and gold standard for what a healthy North Atlantic kelp forest ecosystems should look like.
It’s mid-July 2025 and Nordahl is waiting at the ferry quay on Finnøy. In the water below he spots lurv and some withered seaweed and kelp plants. A familiar sight along much of the coast now, he pins the blame on sewage from a local hotel.
The next day he anchors his boat below Purkeskjæret. Quiet coves on wild skerries provide shelter from the wide-open Norwegian sea. Underwater, steep rock faces plunge to cobbled plains scoured by the rushing tide. A fishing boat is headed for Ona Lighthouse, the last stop before Iceland. As he begins the dive, all looks well. Over the drop-off, where the current tugs at their fronds, the kelps look healthy and vibrant.
But he dives down over the edge and into dismay. Both the kelp and the plains between the islands are covered with robust wigs of lurv. Later that autumn, he shows the visual material he gathered to Christie, who has dived in the same area for the last 25 years. “I’ve never seen such growth there before.” His voice is hushed, mournful, “This is terrible.”
The day after the dive from Purkeskjæret, Nordahl continues the trip by ferry via the small islands on the Atlantic Road. Behind the islands, he passes another fish farm he can't remember seeing before.
Purkeskjæret is no longer an untouched reference point. The resilience of this wild underwater forest, exposed to the open ocean, swept by powerful currents, far from human settlements and their waste, is faltering too.
Not too late
The evidence from around the coast suggests Norway’s great underwater forests are at a tipping point. Sea urchins, lurv and falling oxygen levels are spreading around the coast.
“More work is needed to alert the responsible authorities to how bad it is. It is very serious,” urges Christie. Having spent almost half a century diving and studying Norway’s coastline and fjords, he should know.
He worries that the kelp is beyond saving in several areas. At the same time, he stresses that these rich underwater jungles still maintain resolve elsewhere.
And it is not a lost case. In a study of kelp forests along an urbanised stretch of Australia’s south coast, scientists found that by reducing nutrient runoff and improving wastewater treatment kelp recovery was possible. Although this required considerable initial investments and political will, on a small scale the outcome was highly effective.
By cleaning up the water, the lurv receded and the kelp came back.
In April 2026, Aleksander Nordahl is back in familiar surroundings in Herand, in the Hardangerfjord. A blanket of snow still clings to the mountain slopes. Nordahl slips into ice cold water at the usual spot outside the islands of Herandsholmen and Storeklubben.
Tufts of lurv cling to seaweeds less than a metre below the surface. Here it is flourishing, even in late winter.
Continuing the descent, he reaches a rock plateau at eight metres. The seabed is dotted by a blaze of white sea urchins and scoured bare of all but the hardiest life.
There is kelp here, too. But the kelp sporelings one would expect to see this time of year, the new generation, he cannot find. Their tender growth has been eaten by urchins or smothered by lurv.
With the urge to breathe building, he begins the journey to the surface. On the way up he thinks of how the Hardangerfjord is running low on oxygen too.
Additional credits:
Data analyst and design: Carter Ronald Brown
Data scientist: Alexandra Pires Duro
Additional video and animation: Svein Olav Hyttebakk
Illustrations: Espen Aaeng
Additional design and development: Alicia Harris
Story editor: Ingerid Salvesen
Copy editor: JohnJo Devlin
Digital Producer: Xochitl Vavik
Managing editor and creative director: Aleksander Nordahl
Publisher: Jan Grønbech
Special thanks to external experts Tom N. Pedersen (Senior advisor on aquaculture) and Hartvig C. Christie (Marine biologist and senior scientist), and to Reflections, for whom some of the visuals are taken.