The North Sea is changing; data shows just how quickly

For Anouk Blauw, ecosystem modeller and strategic scientific adviser at Deltares, it is clear: “Observation data by itself is not enough. You need to know what you see.” When Anouk talks about monitoring – the systematic tracking of ecosystems based on observation data – you hear the experience of someone who has been researching marine ecosystems, harmful algal blooms and eutrophication for over twenty years: from the North Sea to the Caribbean.

From a bucket of water to a world full of pixels

Anouk began her career like many marine ecologists: with measurements in a bucket of water. A sample, a lab analysis. “That would yield a single figure,” she explains, “a snapshot that actually says very little about how dynamic the sea is.”

Now she sees the field changing at breakneck speed. Satellite data show the sea as a living, moving pattern of colours and concentrations. Sensors on buoys and ships provide observations every minute, rather than every month.

“Those continuous observations form the basis for monitoring: tracking changes over time. And then there are citizens – surfers, sailors, divers – who use simple sensors to contribute observations from places researchers cannot reach through citizen science."

The beauty of it is that you suddenly see things that were hidden for years. But the tricky part is that much of that data is noisy, inconsistent or contradictory. That’s when the real work begins: interpretation.

Anouk Blauw, expert in monitoring and modeling of marine phytoplankton

Insights that didn’t fit into an Excel spreadsheet

The turning point came when Deltares, together with Rijkswaterstaat, investigated how satellite data could be used for the OSPAR assessments of eutrophication in the North Sea. OSPAR assessments are the official assessments within the framework of the OSPAR Convention (Oslo-Paris Convention) and form the basis of assessments under the Marine Strategy Framework Directive.

They provide insight into the environmental status of the North-East Atlantic, including the North Sea, and are carried out by the fifteen participating countries.

Eutrophication occurs when water contains too many nutrients (mainly nitrogen and phosphorus). This causes algae to grow explosively, resulting in turbid waters, oxygen depletion and ecosystem disruption. In the North Sea and the Wadden Sea, this process is therefore monitored, under the policy frameworks of OSPAR, the Marine Strategy Framework Directive (MSFD) and the Water Framework Directive (WFD).

Anouk compared traditional Excel spreadsheets with observations against satellite images. “When I saw them side by side, gradients and patterns that had previously remained hidden suddenly became apparent,” she explains. “It also showed that monitoring locations, were not often not representative of what we were trying to monitor.”

That observation touched on a broader issue hampering coherent ecosystem assessments: in different countries, field observations were carried out in varying ways, making it difficult to compare results. These issues triggered the international JMP-EUNOSAT project. With Rijkswaterstaat as project coordinator Deltares and European partnersdeveloped a new assessment methodology that combines satellite information, sensor data and model .

And that’s no small feat: you’re asking countries to take a critical look at their familiar ways of working with observations. But when it is clear that differences in approaches undermine comparability, then you simply have to work together to find a better solution.

Anouk Blauw, ecosystem modeller and strategic scientific adviser at Deltares

This method has been applied for the first time in the most recent OSPAR assessments of the North-East Atlantic waters and is also used within the Marine Strategy Framework Directive.

The sea is changing; monitoring must change with it

As if the ecological challenges were not already great enough, the North Sea is now facing a massive transformation: dozens of new wind farms are altering current patterns, food webs and habitats. “This also changes the monitoring task,” says Anouk. “You need to know where these new wind farms have most impact, where you need to measure, how deep and which sensors are suitable.”

Deltares is currently supporting Rijkswaterstaat in the design of a new buoy network in the North Sea: DEM (Digitalisation of Ecological Monitoring). In collaboration with experts from NIOZ, Rijkswaterstaat and the University of Amsterdam we advise which variables need to be observed, and how these observations together provide robust observation data for science, policy and ecosystem assessments.

From nutrients and oxygen to chlorophyll (an indicator of the amount of algae in the water), primary production and sediment, and how this data can be integrated into ecosystem and eutrophication models.

“You don’t just build a network like that,” she says. “It has to be robust and appropriate both for science and policies. That is precisely where scientific knowledge makes the difference.”

Europe wants to work together

The North Sea does not stop at the Dutch border, so Deltares is closely involved in the development of European research infrastructures such as JERICO and DANUBIUS. JERICO is building a joint observation infrastructure for coastal waters across Europe. Within JERICO, Deltares contributes for example to modelling nutrient and carbon cycles in the North Sea, in combination with innovative data from buoys, ferryboxes and satellites.

Anouk was the project leader for the Netherlands within various JERICO projects and contributed to the development of the European coastal observation network, including by drawing up a gap analysis.

“It is absolutely essential that countries adopt the same monitoring approach, using comparable observation strategies, protocols and data processing,” she says. “You cannot make a sound assessment of the Wadden Sea for example if the Netherlands and Germany use different protocols for marine observations.”

Deltares is also closely involved in the development of DANUBIUS (DANUBIUS-RI), the European ‘river-to-sea’ research infrastructure that studies processes across the entire water cycle in an integrated manner. For example, Deltares contributes as partner to the NWO-projectDelta-ENIGMA, which forms the Dutch national node of DANUBIUS.

The EU-wide research project LandSeaLot goes one step further by developing a joint observation strategy for the entire interconnected system of land, coast and sea, including all physical, ecological and human processes that influence one another. It combines field observations, satellite data and models to support better ecosystem understanding and decision-making.

Or as Anouk puts it, referring to LandSeaLot’s motto: "Land-Sea interface: Let’s Observe Together. That is the only way to understand ecosystems that transcend borders." In this project, JERICO and DANUBIUS collaborate with other European research infrastructures, such as ICOS (for carbon observations).

Artificial Intelligence (AI) is accelerating, but the expert explains

The enormous data streams from satellites, buoys and drones call for new methods for data analysis. Artificial Intelligence (AI) and Machine Learning can uncover connections between large datasets that complement each other but are not identical.

“AI can help to identify patterns we would miss otherwise,” says Anouk. “But the interpretation remains a human task. You need to know whether something makes ecological sense, or is simply an artefact of the algorithm or limitations of the dataset.”

That is why AI is not a replacement but rather an enhancer of domain knowledge: without an understanding of hydrodynamics, ecology, optics, statistics and modelling, you cannot assess which correlations are genuine. Deltares can make a significant contribution here, through its combined knowledge of technology and ecosystems.

The future of monitoring: more data, more integration, more insight

When we ask her what monitoring will look like in ten years’ time, she pauses for a moment. Then Anouk says: “I hope that by then we’ll really be working based on information needs. Not: what data do we have available? But: what do we need to know and observe to make scientifically sound policy implemantation? And how do we organise that?”

She sketches a future in which Europe moves towards a single shared observation strategy, in which data flows are designed to be automatically ‘AI-ready’, in which citizen science is reliably embedded, and where policymakers aren’t drowning in raw data but can rely on clear, meaningful insights.

“That is ultimately what we do,” says Anouk. “We help to understand the North Sea, so we can make better choices for the future.”