Assessing the genetic diversity of Baltic Sea stoneworts – setting a framework to support European restoration goals

Text & photos: Roxana Preston

Researchers at Åbo Akademi University are characterising the genetic diversity of stonewort within the Baltic Sea in a bid to help the restoration of shallow, coastal lagoons in Finland.

Shallow, coastal lagoons in the northern Baltic Sea are typically home to stoneworts, a type of green algae. Stoneworts create underwater meadows similar to that of wildflower meadows on land; supporting plants and animals including commercially important fish, and providing ecosystem services important to people. This makes it all the more concerning that stonewort meadows, like many other species, have dramatically declined in the Baltic Sea.

To help tackle the decline in biodiversity throughout Europe, the European Commission has implemented the Nature Restoration Law which sees to restore 20% of the EU land and sea area by 2030. Restoring means returning these environments back to the former, original, normal, or unimpaired conditions. In practice, for stoneworts, that means planting them back into areas where they are either scarce or have been entirely lost.

When performing restoration, it is essential to understand the biology of the species being restored. This includes aspects of habitat preference, tolerance, reproduction, and genetic diversity, amongst other things. Failing to consider these increases the chance of the restoration being unsuccessful.

The Biodiversea team at Åbo Akademi are undertaking several projects to better understand stoneworts, and what is required to restore them. One project, led by researcher Roxana Preston is focusing on genetic diversity and how reproduction influences the structure and connectivity of stonewort populations. The project has been visiting several stonewort meadows in the Åland Islands and southern Finland to collect specimens of two species: baltic stonewort and coral stonewort.

Exactly how stoneworts along the Finnish coastline reproduce is poorly understood and we have very few genetic diversity measurements within the species. Stoneworts, like many plants and algae, have the ability to reproduce in the typical sexual manner with male and female sex cells, but they also have the ability to bypass sexual reproduction and instead create clones of themselves. Individuals produced by sexual reproduction and cloning represent different strengths and weaknesses in terms of fitness and overall survival. These two methods also leave signatures in the genetic diversity of stonewort meadows, which represents the potential to adapt to changing conditions.

Because stoneworts can reproduce in different ways, there are many options in which restoration could be implemented. The question is, whether it is better to replant stonewort meadows using seeds or to introduce armies of clones in the form of branch fragments or bulbs? For restored habitats to be successful they should mirror natural habitats as much as possible. Thus by identifying how stoneworts naturally reproduce and the genetic diversity of their natural populations this project can ensure more successful future restoration.

The project is part of Biodiversea LIFE-IP and supported by the Ministry of Environment. As a SOS project, it supports WP2.1 by identifying strategies and prerequisites for the restoration of important fish nursery habitats.

Author

Roxana Preston, Postdoctoral Researcher, SOS WP2; Project Researcher, Biodiversea LIFE-IP