Macroalgae are macroscopic, multicellular plants that live in aquatic environments, mostly in the benthos. Some macroalgae are perennial, with slower growth rates and delayed reproduction, while other opportunistic species are rapid growing and short lived. Few species are naturally inhabiting the Baltic Sea Proper, mainly fucus, red algae and brown algae. Free floating or beach wrack macroalgae can be collected to support water quality, nutrient recycling and biogas production. They can also be cultivated in nearshore and archipelagic installations and combined with IMTA concepts with other aquaculture activities (fish, mussels).
Beach wrack is the algae species rinsed out to the coast all year round. They are considered as “waste” from a regulatory perspective in many countries and also a “nuisance” to many regions. The removal of beach wrack does not only lead to “cleaner” beaches, with positive impacts to tourism and the local communities, it also contributes substantially to nutrient reduction in the Baltic Sea, as macroalgae show a nitrogen content of 2–6 % of dry weight.
Macroalgae is used already at large scale in food and feed applications, as fertiliser and soil conditioner in agriculture, and as biomaterial (e.g. hydrocolloids or bioplastics). Seaweed can be used for production of nutraceuticals and food antioxidants and for production of energy.
Also, algae cultivation may be used as a method for nutrient and carbon removal from water, and thus contribute to pollution abatement and eutrophication and mitigation of climate crisis. For example, they can also be cultivated in nearshore and archipelagic installations and combined with IMTA concepts with other aquaculture activities (fish, mussels).
Finally, free floating or beach wrack macroalgae can be collected to support water quality, nutrient recycling and biogas production.
Harvesting or hand-picking is spread in many countries, such as Denmark, Sweden and Estonia and it is a tradition for many countries around the world. Harvesting requires a license that is attached to a quota of the amount of seaweed is allowed to harvest and the procedure to follow. Licensing for sustainable harvesting requires analysis of environmental impact assessment to analyse the imposed risks of harvesting. It is a procedure that is followed by many regions or countries.
Biorefining offers development of multiple products from a single biomass resource, and thereby minimising waste production. Biomass is comprised of protein, carbohydrates, secondary metabolites, fats and fibres that can be recovered and used in different product applications, such as food, materials, added-value products, and energy.
Macroalgae is part of ecosystem providing food and shelter to many organisms, it also accumulates nutrients and reduces the eutrophication in the sea. Disturbance of natural balances can have irrepressible adverse effects in the environment. For example, overharvesting of seaweed in the Buck Bay in Poland caused extinction of seaweed natural stocks in the 70s that was never replenished.
Few species are naturally inhabiting the Baltic Sea Proper, with mainly fucus, red algae and brown algae. Several projects are trying to unlock the potential of macroalgae production by identifying conducive condition for macroalgae cultivation. The Interreg BSR GRASS project (2018-2021) is investigating areas where to grow macroalgae in the Baltic Sea. Fucosan Interreg DE-DK is focusing in the German and Danish coastal interface in the Baltic sea. Also, the Swedish project Seafarm is concentrating in cultivating seaweed species in Sweden (mainly West coast).