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Macroalgae aquaculture is thriving, and kelps such as Saccharina latissima, are now farmed over different production sites across Europe. Macroalgae production in integrated multi-trophic aquaculture setups is gaining relevance due to increased biomass yield and bioremediation potential. Nevertheless, there is a substantiated need to understand how this type of production shapes biomass composition. The present study evaluated the influence of time of harvesting and proximity to nutrient source (fish farm sea cages) on the elemental and biochemical composition of S. latissima, with special emphasis on its lipid content. Overall, the differences recorded for elemental, biochemical and lipid composition of S. latissima occurred consistently with harvesting period rather than with the distance to fish farm sea cages, evidencing that farming kelp in integrated multi-trophic aquaculture setups does not compromise nutritional quality while promoting increased biomass yield. Elemental and biochemical composition differed between kelp biomass harvested in April and those harvested in May and June, with lower C, H and carbohydrates, and higher ash contents in the later. Fatty acid profile analysis revealed an increase in monounsaturated fatty acids along the harvesting period, as well as a decrease in n-3 fatty acids with a concomitant increase of the n-6/n-3 ratio from April to May. Statistical analysis of the polar lipidome identified by liquid chromatography-mass spectrometry revealed differences in specific lipid signatures, displaying a perfect discrimination between harvesting periods. The discrimination between samples from reference and integrated multi-trophic aquaculture sites was only observed for kelp biomass harvested in June. Contributing particularly to these differences are betaine lipids, more abundant in the two later time points, and some lysolipid species, especially abundant in June. These findings will allow a more integrated look at macroalgae production under integrated multi-trophic aquaculture framework, thus promoting the systematization of farming practices that may enhance yield with biochemical quality to match the increasing demands by the food industry and sustainable biorefinary pipeline.

The Norwegian coastline covers more than 10° in latitude and provides a range in abiotic and biotic conditions for seaweed farming. In this study, we compared the effects of cultivation depth and season on the increase in biomass (frond length and biomass yield), chemical composition (protein, tissue nitrogen, intracellular nitrate and ash content) and biofouling (total cover and species composition) of cultivated Saccharina latissima at nine locations along a latitudinal gradient from 58 to 69° N. The effects of light and temperature on frond length and biofouling were evaluated along with their relevance for selecting optimal cultivation sites. Growth was greater at 1–2 m than at 8–9 m depth and showed large differences among locations, mainly in relation to local salinity levels. Maximum frond lengths varied between 15 and 100 cm, and maximum biomass yields between 0.2 and 14 kg m−2. Timing of maximum frond length and biomass yield varied with latitude, peaking 5 and 8 weeks later in the northern location (69° N) than in the central (63° N) and southern (58° N) locations, respectively. The nitrogen-to-protein conversion factor (averaged across all locations and depths) was 3.8, while protein content varied from 22 to 109 mg g−1 DW, with seasonality and latitude having the largest effect. The onset of biofouling also followed a latitudinal pattern, with a delayed onset in northern locations and at freshwater-influenced sites. The dominant epibiont was the bryozoan Membranipora membranacea. Our results demonstrate the feasibility of S. latissima cultivation along a wide latitudinal gradient in North Atlantic waters and underscore the importance of careful site selection for seaweed aquaculture.

The aquaculture of macroalgae for human consumption and other high-end applications is experiencing unprecedented development in European countries, with the brown algae Saccharina latissima being the flag species. However, environmental conditions in open sea culture sites are often unique, which may impact the biochemical composition of cultured macroalgae. The present study compared the elemental compositions (CHNS), fatty acid profiles, and lipidomes of S. latissima originating from three distinct locations (France, Norway, and the United Kingdom). Significant differences were found in the elemental composition, with Norwegian samples displaying twice the lipid content of the others, and significantly less protein (2.6%, while French and UK samples contained 6.3% and 9.1%, respectively). The fatty acid profiles also differed considerably, with UK samples displaying a lower content of n-3 fatty acids (21.6%), resulting in a higher n-6/n-3 ratio. Regarding the lipidomic profile, samples from France were enriched in lyso lipids, while those from Norway displayed a particular signature of phosphatidylglycerol, phosphatidylinositol, and phosphatidylcholine. Samples from the UK featured higher levels of phosphatidylethanolamine and, in general, a lower content of galactolipids. These differences highlight the influence of site-specific environmental conditions in the shaping of macroalgae biochemical phenotypes and nutritional value. It is also important to highlight that differences recorded in the lipidome of S. latissima make it possible to pinpoint specific lipid species that are likely to represent origin biomarkers. This finding is relevant for future applications in the field of geographic origin traceability and food control.

To reach the goal of an industrialised macroalgae industry in Norway and other high-cost countries in the near future, a standardised seedling production method to improve quality control and predictability of cultivated biomass is essential. A total of 11 different treatments for seeding twine or rope with meiospores, gametophytes or juvenile sporophytes from the kelp Saccharina latissima were measured for growth (frond length, frond area, biomass yield and density) and protein content after 80 and 120 days at sea. Meiospore- and gametophyte-seeded twines were pre-cultivated in the hatchery for 14–42 days prior to deployment, while juvenile sporophytes of different ages were seeded on ropes directly on the day of deployment using a commercial binder to attach the seedlings. The results showed that seeding with meiospores pre-cultivated in the hatchery for 42 days (S42) before deployment gave significantly longer fronds (77.0 ± 6.7 cm) and a higher biomass yield (7.2 ± 0.1 kg m−1) at sea compared to other treatments. The poorest growth was measured for the direct-seeded sporophytes pre-cultivated in free-floating cultures for 35 days prior to deployment (D35; 34.4 ± 2.4 cm frond length and 1.6 ± 0.4 kg m−1). Image analysis was used to measure the coverage of the twine substrate before deployment, and a correlation was found between substrate coverage and frond length at sea, indicating that this can be used as a tool for quantity and quality control during the hatchery phase and before deployment. The protein content did not reveal any large differences between the treatments after 120 days of cultivation. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

We have evaluated the cultivation potential of sugar kelp (Saccharina latissima) as a function of latitude and position (near- and offshore) along the Norwegian coast using a coupled 3D hydrodynamic-biogeochemical-kelp model system (SINMOD) run for four growth seasons (2012-2016). The results are spatially explicit and may be used to compare the suitability of different regions for kelp cultivation, both inshore and offshore. The simulation results were compared with growth data from kelp cultivation experiments and in situ observations on coverage of naturally growing kelp. The model demonstrated a higher production potential offshore than in inshore regions, which is mainly due to the limitations in nutrient availability caused by the stratification found along the coast. However, suitable locationsareas for kelp cultivation were also identified in areas with high vertical mixing close to the shore. The results indicate a latitudinal effect on the timing of the optimal period of growth, with the prime growth period being up to 2 months earlier in the south (58 °N) than in the north (71 °N). Although the maximum cultivation potential was similar in the six marine ecoregions in Norway (150-200 tons per unit area per year) in the six marine ecoregions in Norway, the deployment time of the cultures seems to matter significantly in the south, but less so in the north. The relevance of the results is discussed with a view towards use in decision support tools and a management context. The results are discussed, focusing on their potential significance for optimized cultivation and to support decision making towards sustainable management. The kelp cultivation potential in coastal and offshore regions of Norway

The article Effect of seeding methods and hatchery periods on sea cultivation of Saccharina latissima (Phaeophyceae): a Norwegian case study, written by Silje Forbord, Kristine B. Steinhovden, Torfinn Solvang, Aleksander Handa, Jorunn Skjermo.

This study represents a large-scale investigation into iodine contents in three commercially important and edible seaweed species from the North Atlantic: the brown algae Saccharina latissima and Alaria esculenta, and the red alga Palmaria palmata. Variability among and within species were explored in terms of temporal and spatial variations in addition to biomass source. Mean iodine concentration in bulk seaweed biomass was species-specific: Saccharina > Alaria > Palmaria. Iodine contents of Saccharina biomass were similar between years and seasons, but varied significantly between sampling locations and biomass sources. In Alaria and Palmaria, none of the independent variables examined contributed significantly to the small variations observed. Our data suggest that all three species are rich sources of iodine, and only 32, 283, or 2149 mg dry weight of unprocessed dry biomass of Saccharina, Alaria, or Palmaria, respectively, meets the recommended daily intake levels for most healthy humans.

New consumer trends, market demands, and opportunities for multiple uses of macroalgae such as food, bioactive components for functional food and feed ingredients, fertilizers, and biofuels have strengthened the motivation for industrial macroalgae cultivation in Europe. The cultivation of kelp in sea requires production of seedlings on substrate to be deployed at sea farms. There are three main strategies for seedling production of kelp, aiming for seeding of the growth substrate with spores, gametophytes, or small sporophytes, whereof seeding with spores and gametophytes so far is the most incorporated techniques. Seeding with spores requires fertile sporophytes and this is seasonally dependent if these are collected in natural habitats, but fertility can also be induced by artificial day rhythm, and thus enables access to spores independent of natural seasons. Gametophytes can be kept in continuous cultures and be available for year-through seeding or production of microscopic sporophytes for direct seeding. This is advantageous as the use of incubation facilities on land can be shortened by several weeks or, in the case of direct seeding, omitted completely. The presented protocol focuses on Saccharina latissima seedlings production from spores and gametophytes and is adapted to the infrastructure and equipment that are available at typical aquaculture research laboratories, although some adjustments may be necessary to meet the needs of the different life stages. Keywords: Saccharina latissima, cultivation, seeding, laboratory protocol, gametophyte cultures, contamination control, deployment

Seaweeds are increasingly used in European cuisines due to their nutritional value. Many algal constituents, such as polyphenols, are important antioxidants and thus considered beneficial to humans. However, many seaweed species can accumulate heavy metals and exhibit potential health risks upon ingestion. We investigated temporal and spatial variations in polyphenol and heavy metal (As, Cd, Hg, Pb) concentrations of three edible seaweed species. The brown algae Saccharina latissima and Alaria esculenta, and the red alga Palmaria palmata were sourced from natural populations and aquaculture in the NE Atlantic and processed as bulk biomass mimicking industrial scales. The mean polyphenol content was species-specific (Alaria > Saccharina > Palmaria), and highest in winter (for Alaria and Saccharina) and spring (for Palmaria); inter-annual and spatial variations were marginal. Heavy metal concentrations varied between species and depended on collection site, but seasonal variations were minimal. Our data suggest that all three species are good sources of antioxidants, and the heavy metal concentrations are below the upper limits set by the French recommendation and the EU Commission Regulation on contaminants in foodstuffs. A health risk assessment indicated that consumption of these seaweed species poses a low risk for humans with regard to heavy metals. However, an EU-wide regulation on maximal concentration of heavy metals in seaweeds should be established.

Integrated multi-trophic aquaculture (IMTA) has the potential of reducing open-cage fish farming impacts on the environment while also introducing new value chains. The aim of this study was to investigate the growth and composition of the kelp Saccharina latissima in salmon-driven IMTA, and to assess the spatial extent of the influence of salmon derived nitrogen in order to evaluate the upscaling potential for IMTA. S. latissima was cultivated 100, 200, and 1,000 m east and 1,000 m west of a 5,000 tons salmon farm in Western Norway from February to September 2013. The proportion of salmon derived nitrogen available for the kelp showed a clear decline with distance from the farm. Accordingly, the kelp cultivated near the salmon cages grew faster during the spring season, and growth rate decreased with increasing distance from the farm. A spatially explicit numerical model system (SINMOD), including compartments for dissolved nutrients and kelp growth, was tuned to the field data and used to investigate the potential for upscaling IMTA production. The model was used to introduce a new metric—the impacted area IA—for the areal effects of IMTA in terms of the increase in production by IMTA. The model showed that a 25 hectare kelp farm in the vicinity of the studied salmon farm could take up 1.6 of the 13.5 tons of dissolved inorganic nitrogen released during kelp cultivation, amounting to almost 12% of the ammonia released during the cultivation period from February to June. The 25 hectare kelp farm would have a production yield of 1,125 tons fresh weight (FW), being 60% more than that of a non-IMTA kelp farm, while a 20% increase of kelp FW could be obtained over a 110 hectar area in salmon-driven IMTA. To achieve an even mass balance, an area of approximately 220 ha−1 would be needed to cultivate enough kelp to fix an equivalent of the nitrogen released by the fish. Copyright © 2018 Fossberg, Forbord, Broch, Malzahn, Jansen, Handå, Førde, Bergvik, Fleddum, Skjermo and Olsen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).

This paper investigated the assimilation of dissolved inorganic nitrogen (DIN) in Saccharina latissima in proximity to salmon cages in coastal waters. The bioassays were performed on plants from three stations located in the vicinity of a salmon farm (Salmo salar) in exposed waters at Tristein (63° 52′ N, 9° 37′ E) in Central Norway. The growth, the C and N content, and the nitrogen isotope ratios (δ15N) of S. latissima were monitored over 1 year. The DIN concentrations in seawater were higher at the salmon farm stations than at the reference station during the winter, and the N/P ratio at the salmon farm stations was higher from September to January and in June. S. latissima at the salmon farm stations grew faster than at the reference station. The length of S. latissima increased by 50 % when integrated with the salmon farm compared to the reference station. The N content of S. latissima was positively correlated to the DIN concentration in seawater (p

The interest to develop an industrialized cultivation of several macroalgae in Europe is growing rapidly. Here, we demonstrate cultivation of the sugar kelp Saccharina latissima in integration with salmon (Salmo salar) aquaculture in a Norwegian coastal area. Sporophytes of S. latissima were deployed at 2, 5 and 8 m depths at a salmon farm and at a reference station 4 km away in August, November, February and June (2010–2011). The growth was good in late autumn and in spring, with peak lengths of the sporophytes in June, while being poor in winter and summer. As a result of a faster initial growth at the fish farm than at the reference station from August to November, the August-sporophytes reached a significantly longer length than those at the reference station in 5 out of 10 sampling months at 2 m depth, and in 9 out of 10 months at 5 m depth (p

A 3-dimensional hydrodynamic−ecological model system (SINMOD) was used to estimate the full-scale cultivation potential of the brown alga Saccharina latissima in integrated multi-trophic aquaculture (IMTA) with Atlantic salmon Salmo salar. A previously developed model for the frond size and composition (carbon and nitrogen content) of S. latissima sporophytes was adjusted to data from an outdoor mesocosm growth experiment and then coupled and run online with the 3-dimensional model system. Results from simulations were compared with data from an IMTA field experiment, providing partial validation of the hydrodynamic–ecological– kelp model system. The model system was applied to study the large-scale cultivation potential of S. latissima in IMTA with salmon and to quantify its seasonal bioremediation potential. The results suggest a possible yield of 75 t fresh weight S. latissima ha−1 in 4 mo (February to June) and about 170 t fresh weight ha−1 in 10 mo (August to June). The results further suggest that the net nitrogen consumption of a 1 ha S. latissima installation in the vicinity of a fish farm producing approximately 5000 t salmon in a production cycle is about 0.36 (0.15) t NH4 +-N, or a removal of 0.34% (0.41%) of the dissolved inorganic nitrogen effluent with a cultivation period from August (February) to June. Due to the differing seasonal growth patterns of fish and kelp, there was a mismatch between the maximum effluent of NH4 +-N from the fish farm and the maximum uptake rates in S. latissima. © The authors 2013. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited.

Saccharina latissima is attractive for industrial cultivation for different usages, such as biofuels, feed supplements, and derivation of chemicals. A continuous supply of kelp sporelings throughout the year may ensure a year-round production of kelp juveniles on ropes. In this study, induction of sporangial areas (sorus portions) on the blade of S. latissima was performed throughout the year at three locations: Trondheim (Norway), Grenaa (Denmark), and Sylt island (Germany). The results indicate that a year-round sorus induction in S. latissima is possible and that this induction is controlled by applying short-day treatment of adult sporophytes throughout the year and by the removal of the basal blade meristem. The artificially induced and released zoospores formed viable sporelings at all seasons, but cultivation in the sea in Norway was successful only during autumn, winter, and spring, while the growth conditions were poor during the summer. The results are important for industrial scale-up and continuous production of kelp biomass.

Increasing global demand for food has generated a need for new strategies to feed a fast-growing population. Oceans appear as a sustainable solution, providing alternative sources of food such as macroalgae. These sea vegetables have high nutritional value and provide functional and health benefits. The sugar kelp Saccharina latissima is an emerging edible seaweed used mainly for human consumption. Although much is known about its biochemical compositions its lipidome remains unexplored. The aim of the present study was to characterize the polar lipid profile of S. latissima using a lipidomic-mass spectrometry HILIC-LC-MS based analysis. This approach allowed the identification of 197 molecular species of polar lipids, including glycolipids, phospholipids and betaine lipids. Several molecular species identified are carriers of polyunsaturated fatty acids with nutritional value and have been reported with anti-inflammatory, anti-microbial and anti-proliferative activity. Saccharina latissima is an emerging candidate to promote blue biotechnology inspired by the ocean.