Sea Rangers start seagrass restoration in Eastern Scheldt

12 Sep 2023 | Dan Benham

Replacing their sailing gear with waders, Sea Rangers have been working in the Eastern Scheldt estuary in the south of The Netherlands to begin important restoration of seagrass meadows. In June, the Sea Rangers joined forces with the University Groningen, for scientific oversight, to transplant 2,232 cores across 13 different local sites, making up over 100,000 seagrass shoots. The team is now monitoring their survival and growth which will help the scientists identify suitable restoration locations.

For the Sea Ranger Service this seagrass restoration project is a huge step towards our larger mission to restore 1 million hectares of biodiversity. In close collaboration with Project Seagrass, University of Groningen, Rijkswaterstaat and other partners, the initial successful planting paves the way to further scale seagrass restoration efforts.

What is seagrass?

Simply put, seagrasses are marine flowering plants that live in shallow waters and tide flats and, similar to  grasses on land, require sunlight to grow. There are 72 different species of seagrass that grow on every continent except Antarctica, all with different characteristics.

In contrast to algae, seagrasses are strongly rooted in the seafloor while their leaves stick up into the water column. They can expand clonally by their rhizomes that branch out just under the surface of the seabed to form new shoots and leaves. Another way through which seagrasses can disperse is by producing and distributing seeds, which grow into new plants that eventually form meadows. Seagrasses are the only flowering plants in the ocean.

Seagrass meadows support high biodiversity of sea life by providing a habitat and nursery to many organisms. Seagrass also has the capacity to absorb CO2 and store it in its structure and in the sediment; a process called carbon sequestration. Some species of seagrass can store more CO2  per hectare than forests. It is surprising how such a small plant has the potential to make a big impact to mitigate the effects of climate change.

How restoration works

Seagrass beds are globally degrading due to human activities in coastal areas. However, when environmental conditions improve, ecological restoration may be a promising strategy to reverse these losses. There are many different methods of seagrass restoration. The first step for Sea Rangers was to dig up small seagrass cores, of 10 cm diameter, with rhizomes and sediment still intact from existing, healthy meadows in the same estuary. This method minimises damage to the original meadow. After a month, the meadow simply grows back the lost seagrass shoots. The collected cores were planted by Sea Rangers at different locations, where periodic monitoring will have to determine its success rate over time.

Sea Rangers will continue a process of planting and monitoring, ultimately researching how environmental factors are influencing the spreading of seagrass in new spots across the Eastern Scheldt estuary. Periodic monitoring will make available a lot of information to determine which locations have the most potential for restoration. This is where Sea Rangers will then focus their seagrass planting efforts over the coming years.

Roosje Lubrecht, one of the Sea Rangers who worked on the project, explains:

During the monitoring days we go out on the mudflats where the seagrass is planted. Even though it was low tide our feet were getting drenched in a mixture of mud and seawater, sometimes sucked into it, barely able to move. We measured how many cores were still present, checked if they had flowers and counted the amount of shoots. Besides making observations of the seagrass we also looked at the surroundings and other factors, such as the presence of lugworms that live in the sediment which may influence seagrass growth. At some locations the seagrass wasn’t doing too well, which at first felt sad, but for the restoration overall this will be a valuable insight into which locations are suitable for future seagrass restoration efforts and which are not. At some locations the cores have already started expanding.”

Why the Eastern Scheldt?

Over the last 40 years, 98% of the seagrass which grew in the tidal flats in the Eastern Scheldt, has disappeared. There is now only 2% of the original seagrass meadows left, an area of 10 hectares. Previous research has shown that sediment stability, exposure time, but also biotic factors such as lugworms, macroalgae and epiphytes can influence the growth and survival of seagrass in the Eastern Scheldt. However in recent years some of these factors have improved, as well as the water quality, providing a positive outlook for restoration. With seagrass meadows decreasing globally, restoration is now more urgent than ever to avoid further biodiversity declines. 

The Sea Rangers are excited to have taken a first step in contributing to regeneration. We hope that these new transplant sites and additional research will shed light on what is needed to enable large-scale and successful long-term restoration of seagrass in the Eastern Scheldt.

Next steps

Over the next few months, Sea Rangers will continue to monitor the growth of their transplants, as well as exploring additional seagrass restoration sites.

With the ambition for Sea Rangers to work in seagrass restoration now fulfilled, Sea Ranger Service founder and CEO, Wietse Van Der Werf, shares his excitement:

The launch of this new project is a big achievement for us and our partners. It represents a huge step forward in our overall mission to restore 1 million hectares of ocean biodiversity. It will be interesting to see how successfully the transplanted seagrass thrives, and how we will replicate the method to other areas.” 

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