European Seagrass Restoration Alliance Conference, Arcachon France

In early April the second European Seagrass Restoration Workshop was held in Arcachon, which was facilitated by the European Seagrass Restoration Alliance (ESRA). ESRA has been founded to bring together seagrass restoration practitioners from across Europe to connect, share ideas and to learn of the scientific research that is being conducted across the continent with the aim to monitor, conserve and restore seagrass. ESRA chose Bassin d’Arcachon as the setting for this year’s gathering as Arachon bay was once home to if not Europe’s largest seagrass meadow than one of them. Restoration Forth’s seagrass officers, Eleri and Lyle were fortunate to attend this year’s gathering. The conference granted them the opportunity to forge connections with members of the UK and European seagrass community and to learn about their respective work. There were many inspiring speakers at this year’s ESRA conference all of whom are involved in exciting and impactful work. The topics of the talks ranged from investigations into the genetics and genomics of seagrasses, remote sensing as a tool for baselining and monitoring seagrass, restoration of cymnodosa nodosa, Posidonia oceanica, Zostera noltii and Zostera marina, wholescale approaches to restoration, societal benefits of seagrass restoration, and nature financing. Additionally, there were sixteen workshops that complimented the themes presented in the talks.

In the following paragraphs I have distilled what I believe to be the three key take home messages from the conference that apply to Restoration Forth. Within each paragraph I share examples of research from talks presented at the conference, that support each point.

The first key point was the need to remove existing pressures that pose a barrier for natural seagrass recovery or impede future active restoration attempts. To recognise and removed point source and non-point source pollution is to ameliorate water quality issues such as elevated nutrient levels and water turbidity. Once these pressures have been identified and mitigated the environment is more susceptible to passive and active forms of restoration. Dr Nicolas Mayot, spoke of the decline of seagrass in the Berre lagoon in Provance France after the development of a hydroelectric dam in the late 1960s. The lagoon prior to the construction of the damn was recorded to have a high diversity of marine flora and fauna, including an extensive seagrass meadow. However, this came to change after increased input of freshwater from the hydroelectric dam into the lagoon. The increase frequency and volume of fresh water being discharged into the lagoon led to the desalination and stratification of the water column along with causing periodic eutrophic events due to increased nutrient loading. This shift in the environment led to a decline in biodiversity in the bay along with a substantial decrease in seagrass extent (Bernard et al., 2005). Over three decades of consultation with EDF, the dam’s owners and operators, the inflow of fresh water into the lagoon was decreased from its 1960’s levels of 105 m3s-1 to 38 m3s-1 in 2025 (Warner, 2012). With the pressure mitigated for the emergence of seagrass started to occur. Bernard et al., 2005) recorded new patches of seagrass within the bay, a sign that the environment had begun to shift. Since then, further restoration work has been conducted in the lagoon. Just this week I have seen social media posts from Richard Lilley, ESRA’s co-founder, that showed Zostera noltii cores being planted in the lagoon. Nicolas’s talk illustrated the benefits of identifying and ameliorating human induced pressures to facilitate the recovery of seagrass. This talk also demonstrated the need to perform this activity first when considering future restoration. There is a growing need for the Forth to have a whole scape approach that does not view the marine environment independent from the land. Management decision made concerning the land ultimately effect the water and there needs to be a joined-up approach if we wish to allow the natural recovery of multiple species and habitats within the Forth’s coastal and marine waters.

A warm welcome from Le Parc naturel marin du Bassin d’Arcachon

Secondly, careful consideration should be taken when selecting a restoration site and when identifying suitable donor meadows to support restoration. Marieke van Katwijk of Radboud University Nijmegen, spoke of a seven ‘jokers’ that should be considered when undertaking restoration, two of those being site and donor meadow selection. Marieke shared results from previous transplant studies conducted in the Dutch Wadden Sea over a 20-year period. From her team’s findings it was evident that seagrass restoration performed best at locations that still possessed seagrass. Moreover, seagrass restoration was still possible in areas that had recently lost seagrass. However, trials conducted in areas that had lost seagrass over longer periods of time were not successful, this reflects the shift in environmental conditions at those locations from being conducive to seagrass growth to presently not being able to support recolonisation. Their results showed that transplants performed better when planted at similar depths to nearby seagrass beds and when habitat requirements (shelter to hydrodynamic forces and salinity) were met (van Katwijk et al., 2009). In relation to sourcing donor material two key points were a) sourcing plants that are adapted to the conditions at the restoration site and b) ensuring genetic diversity of transplants are sufficient to overcome any short-term environmental changes allowing transplanted material to avoid inbreeding (van Katwijk et al., 2009). Identifying donor seagrass meadows that share similar environmental characteristics to the restoration location, will increase the likelihood of the donor seagrass possessing genes able to respond to the new conditions. This is known as phenotypic plasticity, and it is when an organism possesses genes that are able to be expressed in response to short-term or rapid changes experienced the environment. There is work being done across the Mediterranean by Gabriele Procaccini and his research group,  to future proof Posidonia oceanica restoration by sequencing the genomes of populations around the coast of the Med to identify suitable donor meadows, that possess heat stress genes in response to a warming climate. Similarly, work is being conducted out of the research group GEOMAR in Kiel, Germany, to identify solutions to a changing climate in the Baltic Sea. Restoration Forth should look to source donor material from within the Forth or in similar environments if future restoration efforts are to be more successful than previous attempts.

Left: Jana Willim presents results from heat stress tests on Baltic seagrass; right: Gabriele Procaccini presents results from genetics assessments of Mediterranean Posidonia oceanica

Lastly, persevere. To borrow a term that Richard Unsworth, of Project Seagrass, shared during his talk on how to restore common eelgrass (Zostera marina) “there is no silver bullet in seagrass restoration”. This statement emphasised the difficulty in restoring seagrass in dynamic and challenging environments and the need to investigate different avenues when restoring seagrass, as it’s not a one size fits all. His statement exemplified the struggles shared by many in attendance that week, we heard from many speakers share stories of hardship and failure in their attempts to recover seagrass. Failure reporting would grow to be a reoccurring theme within the conference, as many shared their frustrations with scientific journals not accepting publications which did not present positive or ground breaking results. This editorial bias has damaging impacts on the advancement of research in this field, by accepting publications which report failures future studies can make informed decisions based on previous findings. At times restoration may seem like an insurmountable challenge as many setbacks can diminish the spirit of those wishing to recover seagrass. Despite continued setbacks, Diogo Paulo, a researcher at the Centro de Ciências do Mar, and his team were undeterred by successive years of unsuccessful attempts to restore seagrass in a marine park in Portugal. Diogo and his team were experimenting different methods to restore seagrass at scale in the subtidal environment, after a 30ha seagrass meadow disappeared due to recreational boat moorings and clam dredging. Once the marine park was established both these pressures were mitigated. Diogo’s team’s work investigated three factors, donor seagrass species (Cymnodosa nodosa, Zostera marina & Zostera noltii), transplant season (spring, summer & autumn) and source location. Their experiments were subject to multiple storm events and grazing by herbivorous fish, these impacts stymied initial signs of success. In spite of the environmental setbacks, the team were able to draw conclusions from their experiments into which combination of factors was most conducive to succeed. This led the team to develop a 11m2 plot comprising of Zostera marina sods in Spring 2010, as previous smaller planting units did not withstand stressors produced by stochastic events. This plot would remain in-situ until the end of the project in 2018, not only did this plot remain but it increased in size almost 10-fold to a size of 103m2 (Paulo et al., 2019). Their work shed light on the minimum critical size of a planting unit to overcome environmental perturbations and to allow what was an unvegetated site shift to a vegetated one. Diogo’s story was uplifting and inspiring in equal measure. Another bonus on the back of their restoration success was that they were able to submit their article and report on their failures experienced during their research. Restoration Forth needs to seek inspiration from Diogo and his team, perseverance is required if we wish to identify the restoration techniques and areas most susceptible for restoration.

Diogo presenting results from his restoration trials

On a last note, I wanted to mention the talk that inspired me most. The concluding section of the conference covered the societal aspects of seagrass, the first speaker of this section was Wietse van der Werf, the founder and current CEO of the Sea Ranger Service. Wietse spoke of the biggest unaddressed gap in seagrass restoration, social inclusion. Wietse spoke of his own journey and how he was inspired by the Civilian Conservation Corps to found the Sea Ranger Service; an organisation that grants opportunities to young people inside and outside formal education to seek careers in the marine sector. Wietse punctuated his talk of uplifting stories of former recruits who had their lives changed by joining the Sea Rangers, which really resonated with me, as finding a direction in life at such a young age does not come naturally to us all. Having opportunities like the Sea Ranger Service is a fantastic avenue for young people to explore new fields and gain new experiences. The Sea Ranger Service is involved in environmental marine surveying, conservation and restoration by supporting scientific, conservation and government organisations. The Sea Rangers are invaluable to restoration efforts within Europe and now recently the UK with the establishment of the UK branch. The Sea Rangers are committed to restoring 1 million hectares of marine habitats across Europe. They have been integral to seagrass restoration efforts across Europe by providing boots on the ground. If we wish to upscale restoration efforts across the UK and Europe, we will need the people power to make it a reality. Wietse and the Sea Rangers are making this possible.

Meeting up with former colleagues was a highlight of the week

Thanks for reading,

Lyle

Bibliography

Bernard, G., Bonhomme, P., & Boudouresque, C. F. (2005). Recovery of the seagrass Zostera marina in a disturbed Mediterranean lagoon (Etang de Berre, Bouches-du-Rhône, Southern France). Hydrobiologia, 539(1), 157–161. https://doi.org/10.1007/s10750-004-3080-7

Paulo, D., Cunha, A. H., Boavida, J., Serrão, E. A., Gonçalves, E. J., & Fonseca, M. (2019). Open coast seagrass restoration. Can we do it? Large scale seagrass transplants. Frontiers in Marine Science, 6(MAR). https://doi.org/10.3389/fmars.2019.00052

van Katwijk, M. M., Bos, A. R., de Jonge, V. N., Hanssen, L. S. A. M., Hermus, D. C. R., & de Jong, D. J. (2009). Guidelines for seagrass restoration: Importance of habitat selection and donor population, spreading of risks, and ecosystem engineering effects. Marine Pollution Bulletin, 58(2), 179–188. https://doi.org/10.1016/j.marpolbul.2008.09.028

Warner, R. F. (2012). Environmental impacts of hydroelectric power and other anthropogenic developments on the hydromorphology and ecology of the Durance channel and the Etang de Berre, southeast France. Journal of Environmental Management, 104, 35–50. https://doi.org/10.1016/J.JENVMAN.2012.03.011