Seaweed resources of the Baltic Sea, Kattegat and German and Danish North Sea coasts Author Weinberger, Florian Author Paalme, Tiina Author Wikström, Sofia A. text Botanica Marina 2020 Warsaw, Poland 2019-11-12 63 1 61 72 http://dx.doi.org/10.1515/bot-2019-0019 journal article 10.1515/bot-2019-0019 1437-4323 11000049 Harvest of Furcellaria lumbricalis As already recognized by Lehmann (1814) the pristine Baltic Sea environment is characterized by the presence of relatively large amounts of unattached and drifting perennial seaweeds and seagrasses that provide a potential bioresource. In deeper water this resource is often composed of Furcellaria lumbricalis , which up to the present has remained the only seaweed species in the Baltic Sea that is harvested on a commercial scale. Furcellaria lumbricalis has attached and unattached (loose-lying) thallus forms, which represent two distinctive ecotypes ( Kersen 2013 ). The attached F. lumbricalis is widely distributed on hard substrata in the Baltic Sea and can be found at salinities down to 3.6 ( Snoeijs 1999 , Kostamo 2008 , Bučas et al. 2009 , Kersen et al. 2009 , Kostamo et al. 2012 ). The unattached form of the species has a long harvesting history in the Baltic Sea. Its industrial exploitation started in the mid 1940s and lasted until the mid 1960s in Danish waters in the central part of the Kattegat ( Schramm 1998 ). Nowadays unattached F. lumbricalis in the Baltic Sea inhabits only semi-exposed habitats with soft bottoms of the West Estonian Archipelago Sea area ( Martin et al. 2013 ), but outside the Baltic it can also be found in the lochs of Scottish and Irish seas ( Levring et al. 1969 ). The communities of unattached F. lumbricalis previously found in Polish waters ( Schramm 1998 ) disappeared due to elevated eutrophication in the 1980s ( Kruk-Dowgiałło and Szaniawska 2008 ), while intensive harvesting decimated the drifting Furcellaria stocks in the central Kattegat in the 1950s–1970s ( Lund and Christensen 1969 , Schramm 1998 , Pedersen and Snoeijs 2001 ). The Kassari Bay, the western basin of the West Estonian Archipelago Sea still hosts a loose-lying red algal community dominated by unattached forms of Furcellaria lumbricalis and Coccotylus truncatus ( Figure 2 ). The community inhabits sandy and sandy clay substrata, where it forms up to 30-cm thick carpets on seabed at depths of 5–9 m ( Martin et al. 2006b ). The mixed community of loose-lying F. lumbricalis and C. truncatus in Estonia was first described in the early 1960s, and at that time the total biomass was estimated to be 150,000 t wet weight (ww; Kireeva 1961 , 1965 ). More detailed descriptions and assessments of the structure of the community were given by Trei (1978) , who estimated the total community biomass to be 140,000 t wwt, covering an area of 140 km 2 . During the 1980s and 1990s a remarkably lower total biomass and smaller distribution area of the red algal community was observed, which was due to overgrowth by the opportunistic filamentous brown alga Pylaiella littoralis ( Martin et al. 1996 ) . This was followed by a recovery of both the total biomass and the total area of the community, and since 2011 F. lumbricalis stocks in Estonia have remained stable ( Figure 3 ). In 2017 the total community biomass was estimated to be 179,000 t ww. It covered an area of 170 km 2 , with a mean coverage of 78% and a mean thickness of the algal mat of 6 cm ( Paalme 2017 ). On average, Furcellaria lumbricalis accounts for 60–73% ( 612–1010 g m−2 ) and Coccotylus truncatus for 13–25% ( 147–309 g m−2 ) of the total community biomass ( Figure 4 ). Among nine macroalgal species that are associated with the dominating species in the community, the red algae Ceramium tenuicorne and Vertebrata fucoides , the brown alga Battersia arctica and the green alga Chaetomorpha linum were most common ( Pärt 2013 ). Figure 2: Loose-lying Furcellaria lumbricalis-Coccotylus truncatus community in the Kassari Bay, West Estonian Archipelago Sea (Photo: K. Kaljurand). Figure 3: Interannual variation (1980–2017) of the total community biomass (BM), the total Furcellaria lumbricalis biomass and the area of the loose-lying red algal community in the Kassari Bay, West Estonian Archipelago Sea. Data after Martin et al. (2006a) , updated with data of the Estonian Marine Institute on annual monitorings 2003–2017. Figure 4: Interannual variation (2006–2017) of the share of Furcellaria lumbricalis and Coccotylus truncatus in the loose-lying red algal community biomass (BM) in the Kassari Bay, West Estonian Archipelago Sea. Compiled results of annual monitorings 2006–2017; database of the Estonian Marine Institute. Unattached Furcellaria lumbricalis is characterized by relatively slow growth. Its growth rate is primarily affected by factors that alter the light availability for photosynthesis, i.e. seasonality, water transparency, depth and density of the algal community ( Martin et al. 2006a ,b, Kotta et al. 2008 , Paalme et al. 2011 , 2013 ). The commercial utilization of the loose-lying F. lumbricalis and Coccotylus truncatus community in Kassari Bay was started in 1966 by the local company ESTAGAR ( ESTAGAR 2019 ) and until now it has been mostly based on the extraction of furcellaran, that is widely used as a stabilizing, thickening and gelling agent in the food, pharmaceutical, cosmetics and agriculture industries ( Tuvikene et al. 2006 , 2010 , Tuvikene and Robal 2015a , Kersen et al. 2017 ). Furcellarans of F. lumbricalis from the Baltic Sea are characterized by unique chemical composition and properties, as they are a hybrid of κ and β carrageenan ( Tuvikene et al. 2006 , Tuvikene and Robal 2015a ). At present, there is an increasing interest in a new potential biotechnological application of unattached F. lumbricalis biomass as a raw material for extraction of the red pigment R-phycoerythrin ( Tuvikene and Robal 2015b , Kersen et al. 2017 ). Due to its different bioactive properties, R-phycoerythrin can be used not only in the food industry as a natural food colorant, but also in medicine and cosmetics ( Kersen et al. 2017 ). To assure environmentally sustainable and long-lasting utilization of the unique loose-lying red algal community, its ecological status has been monitored regularly, and official regulations of harvesting were introduced since the start of its commercial exploitation ( Martin et al. 1996 ). Currently harvesting by bottom trawling is limited to 2000 t ww per year ( Paalme 2017 ). In addition, beach deposits of both loose-lying and attached communities of Furcellaria lumbricalis are collected for commercial utilisation of carrageenans. Annual losses of the loose-lying F . lumbricalis-Coccotylus truncatus community through wrack deposits were estimated at about 4800 t ww per year, i.e. 4% of the community standing stock ( Kersen and Martin 2007 , Kersen 2013 ).