Kelp Restoration in the Dutch North Sea

Native kelp species such as sugar kelp (Saccharina latissima) and oarweed (Laminaria digitata) have become rare along the Dutch coast, despite their important ecological role. Kelp forests provide structurally complex habitat for fish and invertebrates and contribute to wider ecosystem functioning and biodiversity. This project explored whether active kelp restoration can be technically and ecologically feasible under Dutch conditions. Historical and ecological research was combined with laboratory experiments, semi-natural validation, and field deployments to investigate restoration opportunities.

 

The objective of this project was to identify promising locations and ecological boundary conditions for kelp restoration in the Dutch North Sea, validate scalable restoration techniques under Dutch conditions, and translate the results into practical guidance for future pilots and larger-scale demonstration projects.

Program: Nature Regeneration North Sea (NN)
Image: Kelp that has been growing for 6 months on a stone that was deployed in the NIOZ harbour (2025-2026)

September 2025 – July 2026

Project dates

Laboratory and outdoor facilities on Texel, with field pilots in the NIOZ harbour on Texel, and the Port of Scheveningen. Potential future restoration areas assessed included the Grevelingen, Marsdiep, Oosterschelde, Dogger Bank, Cleaver Bank and Borkum Reef Grounds.

Location

Ebbing Tides Seaweed BV, Wageningen Marine Research, Seawiser BV, MECAL and Campus@Sea. The project was carried out for the Nature Regeneration North Sea programme.

Project lead and partners

Sugar kelp (Saccharina latissima) and oarweed (Laminaria digitata)

Target species

  • Stand-alone structures

Methods

This project followed a staged learning-by-doing approach to investigate whether active kelp restoration is technically and ecologically feasible under Dutch conditions. The study combined historical and ecological research with laboratory experiments, controlled flow testing, outdoor validation, and field deployments. The focus was primarily on sugar kelp (Saccharina latissima), while also considering the potential role of oarweed (Laminaria digitata) in future restoration efforts.

 

Young kelp was produced from traceable Dutch gametophyte cultures and applied directly to a range of substrates using direct-seeding techniques. Substrate-material combinations including MECAL concrete, wood, stainless steel, plastics, and glass were tested to assess their suitability for kelp attachment and growth. The most promising concepts were subsequently evaluated in outdoor and field conditions, using MECAL nodes as recoverable pilot units representing stone substrates.

 

The direct-seeding approach was developed and refined through a series of experiments aimed at improving propagule distribution, attachment, and resistance to hydrodynamic stress. A dedicated flume system was constructed to assess attachment success and seed retention under controlled flow conditions. Additional laboratory experiments investigated the ability of juvenile kelp to grow under low-light conditions representative of deeper or more turbid Dutch waters.

 

Monitoring took place throughout the project and included assessments of sporophyte development, juvenile kelp growth under different light conditions, and densities, substrate attachment, flow resistance, and repeated visual and photographic monitoring of field-deployed substrates. Kelp survival, attachment success, growth and the presence of associated organisms were recorded at the pilot locations.

 

The project also explored the potential integration of kelp with existing and future hard marine infrastructure, including harbour structures, dikes, rock armour, scour protection, and nature-inclusive offshore infrastructure. The use of local genetic material was an important consideration throughout the project to help preserve the genetic diversity of Dutch kelp populations and support future restoration efforts.

Results

This project demonstrates that active kelp establishment under Dutch nearshore conditions is technically feasible while also identifying several important considerations for future restoration efforts. Through laboratory experiments, controlled flow testing and field deployments, the study generated new insights into the environmental conditions, substrates, and techniques that can support kelp restoration in the Dutch North Sea.

 

The results show that juvenile kelp can grow under relatively low-light conditions, indicating that light availability may not be as restrictive as previously assumed in some Dutch coastal environments. Growth was strongly influenced by starting density, with lower-density cultures generally producing larger sporophytes. This highlights the importance of optimising propagule density rather than simply maximising the amount of seed material used during restoration.

 

Substrate characteristics proved to be a key factor in restoration success. Rough and structurally complex surfaces, particularly wood, and stone-like MECAL nodes, supported substantially better attachment and growth than smooth materials such as glass, stainless steel, and flat plastics. These findings suggest that kelp restoration can be effectively integrated with rough mineral structures, including rock armour, scour protection, and other nature-inclusive marine infrastructure.

 

The direct-seeding approach also showed promising results. Kelp remained attached under controlled flow conditions, demonstrating that direct seeding can perform beyond static hatchery environments. Further optimisation is still required, particularly regarding propagule distribution, binder use, and performance under more exposed hydrodynamic conditions, but the results indicate strong potential for future upscaling.

 

Field deployments provided an important proof of concept. Kelp successfully established and developed on artificial substrates at both Texel and Scheveningen, providing the first field validation within this project that hatchery-produced, directly seeded kelp can grow in Dutch coastal environments. In addition, retrieved substrates supported a range of associated marine organisms, demonstrating the potential for kelp-based restoration measures to contribute to habitat complexity and ecological value.

 

The study identified several promising areas for future restoration and demonstration projects. The Texel-Marsdiep region stands out due to successful pilot results, the availability of local genetic material and nearby research infrastructure. The Oosterschelde also shows potential because of its relatively favourable water clarity and historic occurrence of kelp populations, while Scheveningen offers opportunities as an accessible innovation and demonstration site. Offshore locations such as the Dogger Bank, Cleaver Bank, and Borkum Reef Grounds may also be suitable but require additional site-specific assessment before restoration measures can be implemented.

 

While the project successfully demonstrated kelp establishment and early growth, it does not yet demonstrate self-sustaining kelp restoration. Long-term survival, reproduction, natural recruitment and wider biodiversity benefits remain important next steps that should be addressed through larger, multi-year demonstration projects. This will be essential for determining the long-term ecological contribution of kelp restoration in the Dutch North Sea.

Tips & Tricks

 

  • Start small, but design for scaling.
    Laboratory success alone is insufficient for restoration. Accessible nearshore pilots and semi-natural facilities provide an effective intermediate step before moving to larger offshore demonstrations.
  • Surface roughness matters.
    Rough and structurally complex substrates support kelp attachment more effectively than smooth technical surfaces. This should be considered from the earliest stages of nature-inclusive design.
  • More seed is not always better.
    High propagule densities can suppress juvenile kelp growth. Restoration efforts should focus on optimising seeding density rather than maximising it.
  • Use local genetic material whenever possible.
    Traceable local gametophyte cultures help preserve genetic diversity and can form the basis of a living kelp seed bank for future restoration projects.
  • Choose accessible pilot locations.
    Early-stage pilots benefit greatly from locations where monitoring, retrieval and design adjustments can be carried out efficiently.
  • Design experimental structures for retrieval.
    Recoverable substrates facilitate monitoring and improvement while helping to prevent marine litter during testing phases.
  • Establishment is only the first step.
    Successful attachment and growth do not yet demonstrate restoration success. Long-term survival, reproduction and natural recruitment must also be evaluated.
  • Integrate monitoring into project design.
    Features such as identifiable modules, fixed photo locations and removable reference units can improve data collection and support future scaling efforts.

 

Short explanation of the state-of-the-art of kelp domestication, and the potential of kelp.

This video provides an introduction to the potential of kelp as a nature enhancement measure in the North Sea and highlights the research and development activities that underpin kelp restoration efforts. Filmed during a PhD project at NIOZ, the video showcases key insights that contributed to the development of Precision Kelp Farming and ongoing work on kelp restoration and cultivation techniques.

Let's talk

Would you like to know more about this project or get involved? Send an email to the project lead.
alexander@ebbing-tides.com