Coastal municipalities in Lithuania, Poland and Germany are supported by our project experts to find the best installation sites for floating wetlands in order to maximize nutrient removal, gain additional aesthetics benefits to boost tourism and to prevent spatial conflicts of use. Cross-border co-operation along the South Baltic Coast will allow us to test both technological and socio-economical methodologies in different environments.
First floating island were installed in the Curonian lagoon, Darss-Zingst and Szczecin lagoon in 2018 and 2019.
Together with our cooperation partner – the Federal State Institute of Agriculture and Fishery MV – we installed the first two small floating islands in the aquaculture research station in Born at the Darss-Zingst Bodden Chain in 2018. The two floating wetlands, made out of stainless steel mesh filled with reed stems, were planted with a variety of native emergent macrophytes. In the first year we wanted to find out which plants can adapt best to the special site conditions, grow well and remove most efficiently phosphorus and nitrogen from the eutrophicated waters. The islands are installed at the outlet of the aquaculture pond (sturgeon cultivation) and we monitored the water quality as well as nutrient removal in the plant biomass.
Due to the decreasing buoyancy of the islands from last year we installed new modified islands in 2019. This year one island’s floating matrix is made out of thermowood. The other island is again made of a stainless steel mesh which is filled with dry reed stems but this time hollow stainless steel buoys enhance the buoyancy effect. This year we planted macrophytes like purple loosestrife and yellow flag, but also sedges (Carex acutiformis) and rushes (Schoenoplectus lacustris). Both islands help us to avoid plastic utilization – we will see if the buoyancy effect is efficient this year. We will continue the water monitoring and the determination of nutrients in plant biomass this year.
Another installation of a floating wetland is planned for 2020 at the Szczecin lagoon. The municpality Vogelsang-Warsin is fighting with nutrient pollution and E.coli bacteria. A flaoting macrophyte island will be installed behind their pumping station.
Curonian spit national park installed the first active barrier in the Curonian lagoon in 2018. It is a net installation located at Nida in a small bay between two piers. The net, a custom-made floating rig with mesh size > 11 cm, 200 m length and 1 m height, placed at 1 m depth has its structure disposed at whole cross-section of the water column. The buoys as well as anchoring system were made especially for the project purposes. Indigenous plants, such as Common reed (in flower ponds) and willow, were fixed to the net at a minimum spacing of 0.5 m. Local plants were chosen because they might have a highest chance to adapt to the particular environmental conditions of the Curonian lagoon. The growth as well as nutrient accumulation is monitored by students and researchers from Klaipėda University.
In 2019 in the Curonian lagoon close to Juodkrante, two islands each of approximately 32 m² were installed. Both islands’ floating matrixes are made of recycled and UV-resistant hollow plastic (HDPE) pipes, which are covered with coconut coir fiber and fastened using a plastic (PP) mesh. Macrophytes like Common rush, Narrowleaf cattail, Flowering rush or Great manna grass were planted individually between extra hollow pipe spaces.
The floating island in Poland is located in a marina on Wicko Lake, in Wolin National Park in the Szczecin lagoon. This floating, 24 m² matrix is of a similar construction to the island in Lithuania: Hollow HDPE pipes are covered with coconut coir fibres and a mesh of PP holds everything together. Emergent macrophytes like Lakeshore bulrush, Carex riparia, Broadleaf cattail and Iris pseudacorus were planted in the determined hollow spaces.