Kelp forests are among the most productive and species-rich ecosystems in cold seas worldwide. They provide many ecosystem services, including nursery habitats for many fish species, and are essential to marine biogeochemical cycles through the regulation and storage of carbon and nitrogen. Over the past 50 years, many of the world's kelp forests, including those in Scandinavia, have been in decline. The causes are thought to be anthropogenic stressors, including reduced water quality, increased seawater temperatures, overfishing and overgrazing.
What to do
The distribution and density of forests with tangle, Laminaria hyperborea, in the Natura 2000 site Koster- and Väderöfjorden will be monitored using drop-video camera and diving.
The project will investigate and compare two different methods for kelp restoration:
- Green gravel is a cost-effective and simple method that has previously been tested for sugar kelp, Saccharina latissima, in the Gullmarsfjord with promising results. In short, the method involves sowing young seedlings on stones that are allowed to grow under controlled conditions before being transplanted to the area to be restored.
- Pelagic planting is a method developed for commercial kelp farming, whereby the young plants are first grown in the open sea before being transplanted to the seabed. This gives them better environmental conditions for growth and survival, and reduces mortality rates. We believe this method can be particularly beneficial in exposed aquatic environments.
Within the project, we will also investigate the genetic variation in temperature tolerance in local populations of Laminaria hyperborea in so-called "common-garden" experiments, with the aim to breed plants that are more resistant and better adapted to higher water temperatures. This involves growing seedlings from different parents in high temperature water. The best performing plants are then selected as parents for the next generation.
In years 2 and 3, we will examine the effectiveness of the restoration measures by monitoring the distribution and density of the transplanted kelp. We also want to investigate whether transplanted plants survive better in the presence of adult plants. This is of great importance for future decisions on which stands can be restored. Viable kelp forests will benefit the entire ecosystem and lead to a healthier and cleaner ocean, increased biodiversity and better recreational and commercial fishing.
Researchers in the project
Gunilla Toth, senior lecturer at the Department of Marine Sciences.
Kristoffer Stedt, PhD student at the Department of Marine Sciences.