A hectic spring, but everything is going according to plan
The Thriving Bays project is slowly drawing to a close. Most of the work has now been completed, although monitoring will continue for some time to come. In April, sampling in the bays resumed in earnest and will continue until the autumn. As the findings become clearer, work on drafting scientific articles and recommendations is beginning to gather pace.
The measures have been completed in Högklykeviken
Nearly 30 years ago, Högklykeviken on Gräsö had abundant seabed vegetation and was considered to be of very high natural value. When the ‘Thriving Bays’ project began, the water was extremely nutrient-rich and turbid, and the seabed vegetation had largely disappeared. The eutrophication did not originate from land, but appears, by all accounts, to have been caused by previous dredging. When the nutrient-rich clays in the estuary were exposed, phosphorus leakage increased and eutrophication took hold.
To tackle the problem, the project has constructed extensive erosion protection around the dredged area and carried out an aluminium treatment to re-bind the phosphorus in the sediment. The treatment has been divided into several small doses administered at different times so that the researchers can monitor and evaluate how the effect of the measure develops. The original plan included a further small dose of aluminium in a shallow part of the bay, but the researchers have decided to refrain from this.
“The falling phosphorus levels in the bay show that the treatment is working well,” says project manager Linda Kumblad. “This part of the bay has also been treated before, and adding more treatment would not make much difference. What’s more, it is so shallow that the turbidity caused by the workboat would probably disrupt both the ecology and the measurements we are taking.”
The measures in Högklykeviken are now complete. Sampling and monitoring will continue as usual until 2027 to keep track of developments in the bay and assess the impact of the measures implemented.
The researchers decided to cancel the final scheduled aluminium treatment in Högklykeviken. Photo: Linda Kumblad
A third year of water regulation in Långbroviken
In Långbroviken on Värmdö, the project has implemented another measure. Here, researchers suspected that the bay’s poor environmental status was caused by strong water flows from the bay’s mouth, which were causing seabed erosion. To investigate whether a reduced flow could reduce erosion, a metal plate was placed at the mouth. The measure was carried out in the spring when the flow is at its peak, and local residents were able to accept that the boat route was closed.
The first trial in 2024 yielded promising results, with clearer water, lower nutrient levels and positive effects on the fish community as well. Following the trial in spring 2025, the results were less clear, which is why it was decided to carry out another closure this year. The metal plate will remain in place until midsummer.
“It took a great deal of detective work to understand what had caused the sudden rise in levels in 2025,” explains Emil Rydin, one of the researchers on the project. “We now have a better understanding of the various sources of nutrients, and we hope to see clearer results from this year’s trials.”
For the third spring in a row, the artificial sill was set up at the road bridge over the mouth of Långbroviken. Photo: Linda Kumblad.
Fiskeförbud året om föreslås för Toren
In Toren, in the municipality of Haninge, residents have experienced problems with the rapid growth of underwater vegetation, which has made it difficult to use boats. Rather than dredging away all the vegetation and risking damage to the bay’s environment, they decided, in consultation with researchers, to install a communal boat channel. This has now been working well for several years.
“There is now also a proposal to introduce a year-round fishing ban in Toren,” says Joakim Hansen, a researcher on the project. “The hope is that reduced fishing will lead to more predatory fish, which can help restore a better balance in the bay, with fewer small fish, more small creatures that graze on algae, and consequently less algae growth.”
The small marina in Toren. Photo: Naturvatten AB
40 million for coastal restoration research programme
The Mistra Research Foundation is now investing up to 40 million kronor in the new Back2Future research programme, which is set to lay the foundations for a national centre for coastal restoration. This initiative builds on the experience gained from Thriving bays and other restoration projects, enabling the knowledge that has been developed over many years to be collated and further developed – and making it more accessible to local authorities, county councils and other local stakeholders wishing to restore their coastal environments.
“Thriving bays has demonstrated how complex coastal environments can be restored. We are now building on that knowledge to strengthen Sweden’s capacity to restore natural environments in a time of rapid change,” says Linda Kumblad, project manager for Thriving bays and programme director for the new Mistra Back2Future programme.
Multiple articles and presentations
There is a lot going on within the project. Here are a few examples from the spring.
- A research article has been published about the time Åsa Austin, a researcher on the project, took part in an art-science collaboration at Berwaldhallen. There, she recited a text about shallow bays that had been set to music by a composer.
- Two scientific articles have been completed and submitted to scientific journals – one on cultural ecosystem services from shallow bays and one on the impact of recreational boats on turbidity. Work has begun on several more.
- Linda Kumblad, project manager, and Emil Rydin, researcher within the project, were awarded the Water Academy’s honorary prize for their “outstanding contribution to public education”.
- To make the project’s findings accessible, Levande vikar is producing a series of popular science fact sheets. Work on the first fact sheet – of around eight – has begun and is expected to be completed after the summer.
- The large research consortium CoastClim, which studies the Baltic Sea from a climate perspective, used the well-studied project bays of Thriving bays for a major study of how various greenhouse gases are emitted and absorbed in these shallow areas: Large variations in greenhouse gas emissions from shallow coastal bays.
- An article on the findings of a Master’s student who has been studying the consequences of fishing bans in the project’s bays: When danger lurks everywhere.
In addition, the researchers have taken part in several events to present the work carried out within the Thriving bays project to a wide range of audiences, including local residents, project coordinators, politicians and international researchers.