Green islands in blue lagoons: chances and research

Lagoons along the South have EUTROPHICATED LAGOONS been heavily impacted by humans for decades and too many nutrients have Overly enriched water with minerals and accumulated in the water and sediments. nutrients, mainly nitrogen and phosphorus, Therefore, actions have to be taken in can induce excessive growth of algae. So order to achieve a good ecological status called eutrophication can consequently required by the EU Water Framework cause oxygen depletion, which can lead to Directive. One option to remove the a degeneration of the coastal environment nutrients is phytoremediation and the use with e.g. plant overcrowding, fish kills and of 'active barriers' such as floating odour issues. The origin of nutrient inputs macrophyte islands. are mainly from wastewater treatment facilities, runoff from land during rains and ice melting, farming and aquaculture.

Major pathways of nutrients in a system with a floating macrophyte island FLOATING INSTALLATIONS FOR FLOATING WETLANDS ARE NUTRIENT MITIGATION A GENUINE ALL-ROUNDER

At floating installations, emergent The green islands create diverse habitats macrophytes are planted on a floating for birds, insects and fish and can matrix. The plant roots in the water column represent local biodiversity hotspots. directly absorb nutrients such as There, protected red listed plant species phosphorus and nitrogen and incorporate can grow undisturbed and, at the same them into their tissues through time, by integrating nice flowering species, biosynthesis and release oxygen into the the attractiveness of the location can be water. Furthermore, bacteria associated to raised. Additionally, the islands' harvested the plant roots transform nitrate to biomass can be used as animal feed, fuel molecular nitrogen which can leak as a or building material (e.g. for thatched roofs gas from the Baltic Sea and cannot be or as insulating material). Also, floating used directly as a nutrient anymore. islands attenuate wave energy and water Moreover, the reduction of nutrients can flow and thus enhance particle settling and directly facilitate the reduction of algal nutrient burial. biomass. Additionally, due to shading of the water, its temperature will be regulated and light availability for extensive algal growth will be limited.

Scheme of a floating macrophyte island PILOT INSTALLATION SITES Indigenous plants, such as Common reed (in flower ponds) and willow, were fixed to Floating islands with emergent the net at a minimum spacing of 0.5 m. macrophytes such as sedges, cattail, reed, The floating barriers are expected to yellow and sweet flag or purple and yellow protect swimming areas from debris, loosestrife have been installed, maintained seaweeds, erosion, excessive silt and and harvested in different lagoons along sediment concentrations. the South Baltic since 2018. The plant roots of so called emergent macrophytes are in the water, but the leaves are above the water surface.

Floating macrophytes islands sites in LiveLagoons Juodkrante and Nida () Installation sites in Lithuania In the close to Wolin National Park (Poland) Juodkrante, two islands each of approximately 32 m² were installed at the beginning of May 2019. Both islands' The floating island in Poland is located in floating matrixes are made of recycled and a marina on Wicko Lake, in Wolin National UV-resistant hollow plastic (HDPE) pipes, Park in the Szczecin lagoon. This floating, which are covered with coconut coir fiber 24 m² matrix is of a similar construction to and fastened using a plastic (PP) mesh. the island in Lithuania and was installed at Macrophytes like Common rush, the end of April 2019: Narrowleaf cattail, Flowering rush or Great manna grass were planted individually between extra hollow pipe spaces. Additionally, a net was placed as an active barrier in a small bay between two piers in Nida. 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 Installation site in Poland its structure disposed at whole cross- section of the water column. Hollow HDPE pipes are covered with ABOUT THE PROJECT coconut coir fibres and a mesh of PP holds everything together. Emergent The aim of this three year project is to macrophytes like Lakeshore bulrush, improve water quality using floating Carex riparia, Broadleaf cattail and Iris wetlands and to help create bathing pseudacorus were planted in the conditions inside the South Baltic lagoons, determined hollow spaces. where algal blooms and sediment Born (Germany) resuspension prevent recreational bathing. Coastal municipalities are supported by our project experts to find the best Two islands of 4 m² were installed in Born installation sites for the floating wetlands in within a drainage flowing into the so called order to maximize nutrient removal, gain bodden water in April 2018 and 2019. additional aesthetic benefits to boost One island's floating matrix is made out of tourism and prevent spatial conflicts of thermowood. With this thermally modified use. Cross-border co-operation along the spruce wood the durability and buoyancy South Baltic coast will allow us to test both is enhanced. The other island is made of a technological and socio-economical stainless steel mesh which is filled with dry methodologies in different environments. reed stems and hollow stainless steel LiveLagoons is supported by the Interreg buoys to enhance the buoyancy effect. South Baltic Programme 2014-2020 and Macrophytes such as the beautiful co-financed by the European Regional flowering Purple loosestrife and Yellow Development Fund. flag, but also Lesser pond-sedges and Lakeshore bulrush were pre-grown on coconut coir fibers mats and were laid on Lead partner: the floating matrixes. Klaipeda University (Lithuania) Contact: Dr. Arturas Razinkovas-Baziukas Project partners: EUCC - The Coastal Union Germany e.V. (Germany) IBW PAN - Institute Of Hydro-Engineering Of The Polish Academy Of Sciences

Installation sites in Germany (Poland) National Park (Lithuania) www.balticlagoons.net/livelagoons

“The contents of this factsheet are the sole responsibility of the authors and can in no way be taken to reflect the views of the European Union, the Managing Authority or the Joint Secretariat of the Interreg V A South Baltic Programme 2014-2020.“