Our vision

Meet our CEO, Daniel Lux, in this film presenting the vision and plans of Oxygen Valley and how we will work to restore life below water with Mariager Fjord in Denmark as a lighthouse project.

Here, ‘lighthouse project’ means a flagship demonstration project that tests new solutions at full scale and shows how environmental restoration can be done in a way that can guide future restoration efforts in Denmark and beyond

The environmental state of Danish fjords

Many Danish fjords experience recurring and sometimes severe oxygen depletion. When this happens, the seabed can be heavily affected: dark mud builds up on the bottom, and white bacterial layers can form where low‑oxygen water meets oxygen‑rich water. If low‑oxygen conditions last for a long time, poisonous hydrogen sulfide can build up near the bottom, and nutrients such as nitrogen and phosphorus can leak from the sediments back into the water. This “internal loading” can keep the water nutrient‑rich and delay the recovery of the ecosystem, especially in fjords with strong stratification of the water column.

In recent years, oxygen depletion has affected many Danish fjords and coastal waters, and only a minority currently meet the criteria for good ecological status (see the latest national assessments for coastal waters and marine areas on the Danish authorities’ websites: coastal waters under the Water Framework Directive and marine areas under Denmark’s Marine Strategy)

Reduced fish stocks and biodiversity

DTU Aqua has documented a dramatic decline in fish populations in Danish fjords over the past 100 years. For example, in fjords such as Mariager, Vejle, Isefjord, and Roskilde, the abundance of flounder today is only around one-fifth of what it was 100 years ago. In addition, species such as cod and eelpout have become rare in many Danish fjords.

For additional information, you can consult:

Severe ecological impacts

Monitoring data and scientific studies show that ecosystems in several Danish fjords are in very poor condition, with clear signs of severe ecological degradation. In some fjords, eelgrass has largely disappeared and other life on and in the seabed, such as clams and worms, have been heavily impacted in areas affected by repeated oxygen depletion.

For additional information, you can consult:

Persistent nutrient load

Despite many years of efforts to reduce nutrient discharges, nitrogen and phosphorus levels in many Danish fjords and coastal areas remain too high, and in the last decade the overall nitrogen load to coastal waters has changed very little.

For more background, see

With the recent Grøn Trepart agreement, Denmark has now decided on a new, more targeted nitrogen strategy that combines land‑use change and improved wastewater treatment to reduce nitrogen inputs to fjords and coastal waters and help meet the EU Water Framework Directive goals for good ecological status (see the government’s agreement on Den Grønne Trepart and the updated river basin management plans).

Alarming hypoxic state

Oxygen depletion in Danish waters has reached extremely worrying levels. In late September 2023, Aarhus University (DCE) reported that oxygen‑poor water covered one of the largest areas seen in decades, including parts of Limfjorden, Mariager Fjord and the southern Little Belt. A major storm in October helped for a while, but serious low‑oxygen zones remained in several fjords.

In September 2024, the situation was even worse: oxygen depletion covered an area of the inner Danish waters larger than Zealand and Funen combined.

At Oxygen Valley, we work to develop and implement solutions that can help restore healthy ecosystems in Danish fjords

For more background, see

Our “Life Below Water” Mission

“Life below water” is one of the UN Sustainable Development Goals and is about conserving and sustainably using the world’s oceans, seas, and marine resources for sustainable development. In a Danish context, this also links closely to the health of fjords and lakes.

At Oxygen Valley, this goal is our core purpose.

With Mariager Fjord as our concrete starting point, we work to turn knowledge into action that can restore and protect life under water.

The goal focuses, among other things, on protecting marine and coastal ecosystems and ensuring that there is life under water also for future generations.

At Oxygen Valley, this goal is our core purpose.

With Mariager Fjord as our concrete starting point, we work to turn knowledge into action that can restore and protect life under water.

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From problem to resource

Vi vil gennem projekter bidrage til genopretningen af økosystemet.

We will, through collaboration, bring back rich plant and animal life.

We will strengthen research and share knowledge in the field.

We will be a catalyst for innovation collaborations across research, business, authorities, and local communities.

KnowHow2 Academy

Oxygen Valley will contribute to the restoration of healthy ecological conditions in Mariager Fjord and beyond. We share our knowledge from research and innovation locally and globally along the way, so that our knowledge can be applied to life in freshwater more broadly, in lakes and fjords.

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