| 1. |
- Afanasyev, Dmitry, et al.
(author)
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Vegetation of the supralittoral and upper sublittoral zones of the Western German Baltic Sea coast: a phytosociological study : Vegetation of the Western German Baltic Sea coast
- 2022
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In: Botanica Marina. - : Walter de Gruyter GmbH. - 0006-8055 .- 1437-4323. ; 65:2, s. 121-33
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Journal article (peer-reviewed)abstract
- Supralittoral and shallow water seaweed communities are particularly exposed to impacts such as climate change and disturbance by humans. Therefore, their classification, the study of composition, and the monitoring of their structural changes are particularly important. A phytosociological survey of the supralittoral and upper sublittoral vegetation of the South West Baltic Sea revealed eight phytobenthos communities with two variants comprising 35 taxa of macrophytes (18 taxa of Chlorophyta, 13 taxa of Rhodophyta and four taxa of Phaeophyceae, Ochrophyta). Five of the eight communities were dominated by Ulvales (Ulva intestinalis, Kornmannia leptoderma, and three Blidingia species), the other three by Fucus vesiculosus. Most Fucus vesiculosus-dominated communities contained U. intestinalis and U. linza as subdominants. Only one of the communities had until now been described as an association (Ulvetum intestinalis Feldmann, J. (1937). Les algues marines de la Cote des Alberes. Rev. Algol. 9: 141–335). The syntaxonomic composition of the investigated vegetation includes both phytocenoses with the domination of green algae (Ulvetum intestinalis Feldmann, J. (1937). Les algues marines de la Cote des Alberes. Rev. Algol. 9: 141– 335 and communities of Blidingia marginata, unidentified Blidingia spp. and Kornmannia leptoderma), as well as a number of communities dominated by Fucus vesiculosus. Mainly boreal Atlantic species and cosmopolitans make up the bulk of the species in these associations.
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| 2. |
- Cai, Chuner, et al.
(author)
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Screening and verification of extranuclear genetic markers in green tide algae from the Yellow Sea : Extranuclear markers in green tide algae
- 2021
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 16:6
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Journal article (peer-reviewed)abstract
- Over the past decade, Ulva compressa, a cosmopolitan green algal species, has been identified as a component of green tides in the Yellow Sea, China. In the present study, we sequenced and annotated the complete chloroplast genome of U. compressa (alpha-numeric code: RD9023) and focused on the assessment of genome length, homology, gene order and direction, intron size, selection strength, and substitution rate. We compared the chloroplast genome with the mitogenome. The generated phylogenetic tree was analyzed based on single and aligned genes in the chloroplast genome of Ulva compared to mitogenome genes to detect evolutionary trends. U. compressa and U. mutabilis chloroplast genomes had similar gene queues, with individual genes exhibiting high homology levels. Chloroplast genomes were clustered together in the entire phylogenetic tree and shared several forward/palindromic/tandem repetitions, similar to those in U. prolifera and U. linza. However, U. fasciata and U. ohnoi were more divergent, especially in sharing complementary/palindromic repetitions. In addition, phylogenetic analyses of the aligned genes from their chloroplast genomes and mitogenomes confirmed the evolutionary trends of the extranuclear genomes. From phylogenetic analysis, we identified the petA chloroplast genes as potential genetic markers that are similar to the tufA marker. Complementary/forward/palindromic interval repetitions were more abundant in chloroplast genomes than in mitogenomes. Interestingly, a few tandem repetitions were significant for some Ulva subspecies and relatively more evident in mitochondria than in chloroplasts. Finally, the tandem repetition [GAAATATATAATAATA × 3, abbreviated as TRg)] was identified in the mitogenome of U. compressa and the conspecific strain U. mutabilis but not in other algal species of the Yellow Sea. Owing to the high morphological plasticity of U. compressa, the findings of this study have implications for the rapid non-sequencing detection of this species during the occurrence of green tides in the region.
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| 3. |
- Cardoso, Isabel, et al.
(author)
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Salinity as a tool for strain selection in recirculating land-based production of Ulva spp. from germlings to adults
- 2023
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In: Journal of Applied Phycology. - 0921-8971.
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Journal article (peer-reviewed)abstract
- The genus Ulva is globally distributed and has been thoroughly studied because of its functional biochemical composition, rapid growth rates and opportunistic features, and interest in Ulva cultivation is growing worldwide. In Europe, mostly near- and on-shore flow-through cultivation systems are used, and land-based recirculating aquaculture systems (RAS) using fresh water or artificial seawater have not been developed for Ulva. While RAS provides quality control and can be located inland, maintenance costs are high. Using selected strains adapted to low-salinity could reduce seawater production costs and improve the economic feasibility. Therefore, our study assessed how salinity can be used as a tool for strain selection and optimization of functional traits. Growth rates and antioxidant activity of three species (four strains) of tubular and foliose Ulva from the NE-Atlantic and Mediterranean (foliose: Ulva lacinulata – two geographical strains, tubular: Ulva linza and Ulva flexuosa) were followed for three weeks at salinities ranging from 10 to 30 PSU. The tubular strains achieved optimal growth at a lower salinity than U. lacinulata. However, growth rates of both foliose strains were higher than of tubular strains, even at sub-optimal salinity. Therefore, U. lacinulata is a good candidate for RAS with artificial seawater, and the cost of salt can be reduced by up to 33.3% (20 PSU) without significantly reducing the growth rate of U. lacinulata. Higher antioxidant activity was achieved by reducing the salinity to 10 PSU for 10 days, suggesting that the functional traits of cultivated Ulva lacinulata can be optimized prior to harvest.
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| 4. |
- Hoffmann, Laurie, et al.
(author)
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The green seaweed Ulva: tomorrow’s “wheat of the sea” in foods, feeds, nutrition, and biomaterials
- 2024
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In: Critical reviews in food science and nutrition. - 1040-8398.
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Research review (peer-reviewed)abstract
- Ulva, a genus of green macroalgae commonly known as sea lettuce, has long been recognized for its nutritional benefits for food and feed. As the demand for sustainable food and feed sources continues to grow, so does the interest in alternative, plant-based protein sources. With its abundance along coastal waters and high protein content, Ulva spp. have emerged as promising candidates. While the use of Ulva in food and feed has its challenges, the utilization of Ulva in other industries, including in biomaterials, biostimulants, and biorefineries, has been growing. This review aims to provide a comprehensive overview of the current status, challenges and opportunities associated with using Ulva in food, feed, and beyond. Drawing on the expertise of leading researchers and industry professionals, it explores the latest knowledge on Ulva’s nutritional value, processing methods, and potential benefits for human nutrition, aquaculture feeds, terrestrial feeds, biomaterials, biostimulants and biorefineries. In addition, it examines the economic feasibility of incorporating Ulva into aquafeed. Through its comprehensive and insightful analysis, including a critical review of the challenges and future research needs, this review will be a valuable resource for anyone interested in sustainable aquaculture and Ulva’s role in food, feed, biomaterials, biostimulants and beyond.
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| 5. |
- Juul, Louise, et al.
(author)
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Combining pressing and alkaline extraction to increase protein yield from Ulva fenestrata biomass
- 2022
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In: Food and Bioproducts Processing: Transactions of the Institution of of Chemical Engineers, Part C. - : Elsevier BV. - 1744-3571 .- 0960-3085. ; 134, s. 80-85
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Journal article (peer-reviewed)abstract
- Many seaweed species have a high production potential and attract interest as future protein sources. A high fiber and ash content, however, demand extraction of the protein to improve its digestibility and protein utilization in food or feed. This study explores three different approaches for protein extraction from Ulva fenestrata in order to maximize the protein extraction yield. Soluble protein was recovered either by mechanical pressing or by homogenization and osmotic shock of the biomass followed by alkaline extraction. The soluble protein was then concentrated by isoelectric precipitation. A combined procedure was carried out by pressing the biomass and following subjecting the residual pulp fraction to homogenization, osmotic shock and alkaline extraction. The three methods were ranked as follows with respect to protein extraction yield (as % of biomass protein); the combined method (23.9 ± 0.3%)> the alkaline extraction (6.8 ± 0.2%)> mechanical pressing (5.0 ± 0.2%). The significant increase when combining the methods was ascribed to a high precipitation yield after alkaline extraction of the pulp, hypothesized to be due to a reduced conductivity of the alkali-soluble protein fraction when derived from pulp rather than whole biomass.
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| 6. |
- Juul, Louise, et al.
(author)
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Ulva fenestrata protein – comparison of three extraction methods with respect to protein yield and protein quality
- 2021
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In: Algal Research. - : Elsevier BV. - 2211-9264. ; 60
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Journal article (peer-reviewed)abstract
- Seaweed is gaining attention as a possible alternative and sustainable source of proteins. This study investigates three protein extraction methods and their effect on protein yield and quality when applied to Ulva fenestrata . Two of the methods included alkaline extractions (pH-shifts); one version solubilizing the proteins at pH 8.5 and one solubilizing them at pH 8.5 followed by pH 12 (pH 8.5+12). The third method was a mechanical pressing, using a double screw press. All extraction methods were followed by isoelectric precipitation to concentrate the proteins. Extraction at pH 8.5 gave the significantly highest total protein yield after the isoelectric precipitation, followed by extraction at pH 8.5+12 and lastly mechanical extraction gave the lowest yield. Proteins extracted with both alkaline methods had a significantly higher solubility at pH 7 and pH 9, compared to proteins from the mechanical pressing. There were no significant differences between the three methods in total D/L-amino acid ratio. Amino acid cross-links measured as lysinoalanine (LAL) and lanthionine (LAN) where found in significantly higher amounts in alkali-extracted proteins compared to mechanically extracted, however not to a degree that expect to compromise functional or nutritional quality. Further, no significant difference in protein in vitro digestibility was found between extraction methods. In conclusion, results indicated that protein extraction at pH 8.5 can be recommended, especially regarding total protein yield and solubility of the final protein extract.
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| 7. |
- Olsson, Joakim, 1988, et al.
(author)
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Cultivation conditions affect the monosaccharide composition in Ulva fenestrata
- 2020
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In: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 32, s. 3255-3263
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Journal article (peer-reviewed)abstract
- In recent years, the interest in using seaweed for the sustainable production of commodities has been increasing as seaweeds contain many potentially worthwhile compounds. Thus, the extraction and refining processes of interesting compounds from seaweeds is a hot research topic but has been found to have problems with profitability for novel applications. To increase the economic potential of refining seaweed biomass, the content of the compounds of interest should be maximized, which can potentially be achieved through optimization of cultivation conditions. In this study, we studied how the monosaccharide composition of the green seaweed species Ulva fenestrata is influenced by the abiotic factors; irradiance, temperature, nitrate, phosphate, and pCO(2). It was evident that lower nitrate concentration and cultivation at elevated temperature increased monosaccharide contents. A 70% increase in iduronic acid and a 26% increase in rhamnose content were seen under elevated irradiance and temperature conditions, though the absolute differences in monosaccharide concentration were small. Irradiance and nitrate impacted the ratio between iduronic and rhamnose, which is an indicator of the ulvan structure. These results could potentially be utilized to coax the ulvan towards specific bioactivities, and thus have a considerable impact on a potential biorefinery centered around Ulva.
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| 8. |
- Olsson, Joakim, 1988, et al.
(author)
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Effects of geographical location on potentially valuable components in Ulva intestinalis sampled along the Swedish coast
- 2020
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In: Applied Phycology. - : Informa UK Limited. - 2638-8081. ; 1:1, s. 80-92
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Journal article (peer-reviewed)abstract
- Macroalgal biomass has the potential to become an important source of chemicals and commodities in a future biorefinery. Currently, production of macroalgal biomass is expensive and the content of high-value compounds is often low. Therefore, in this study the biochemical composition of Ulva intestinalis along the Swedish west coast and the east coast up to Stockholm was assessed with the aim of determining how the content of potentially valuable compounds, such as rhamnose, iduronic acid and PUFAs, could be maximized by utilizing natural variation in the choice of marine cultivation site. Along the investigated coastline, the salinity dropped from 19.4‰ at high latitudes along the west coast to 5.4‰ at Stockholm. Nitrogen and phosphorus availability varied, while temperature was similar at all locations. The two major components of biomass, carbohydrates and ash, varied inversely with the highest content of ash in the west and carbohydrates in the east. In addition, total fatty acids were significantly higher in west coast samples at 3.2 g 100 g–1 dw, with a higher proportion of mono- and polyunsaturated fatty acids. Some health-beneficial fatty acids were found, including EPA and DPA, at 10–50 mg 100 g–1 dw, respectively. The metal content and elemental composition varied widely, probably due to the influence of specific local conditions. The P content was correlated with the phosphorus concentration in waters at the locations. In PCA analysis, the monosaccharides constituting the cell wall polysaccharide ulvan were found to vary by geographical location, with higher levels possibly associated with lower salinities. However, only glucuronic acid differed significantly between sites. These results show the considerable geographical variability in the composition of Swedish U. intestinalis and suggest that different salinities could be used to create a lipid- or carbohydrate-rich biomass.
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| 9. |
- Stedt, Kristoffer, 1991, et al.
(author)
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Cultivation of seaweeds in food production process waters: Evaluation of growth and crude protein content
- 2022
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In: Algal Research. - : Elsevier BV. - 2211-9264. ; 63
-
Journal article (peer-reviewed)abstract
- There is an increasing demand for sustainably produced, protein-rich, and nutritious food. Seaweeds are promising protein sources for the future if their protein content can be optimized, something which can be achieved by cultivation in elevated nutrient concentrations. Cultivation of seaweeds in integration with fish farms have received much attention lately, but using nutrient-rich process waters from other food industries as feed stock for seaweed has rarely been studied. Here, we demonstrate a simple and sustainable strategy to answer the increasing world demand for food rich in plant-based proteins by connecting food production process waters with seaweed cultivation. We compared growth rates and crude protein content of four different seaweed species, the brown species Saccharina latissima, and the green species Ulva fenestrata, Ulva intestinalis, and Chaetomorpha linum, when cultivated in two dilutions (providing 20 and 200 μM ammonium) of eight different process waters emerging from recirculating salmon aquaculture systems as well as from herring, shrimp and oat processing. Growth rates of the green seaweeds were up to 64% higher, and crude protein content was almost up to four times higher when cultivated in the food production process waters, compared to seawater controls. Growth rates were generally higher in presence of 20 μM compared to 200 μM ammonium, while crude protein content was either unaffected or positively affected by the increasing ammonium concentration. This study indicates the potential for cultivating seaweeds with food production process waters to generate additional protein-rich biomass while nutrients are being circulated back to the food chain. A new nutrient loop is thus illustrated, in which the costly disposal of food production process waters is instead turned into value by seaweed cultivation.
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| 10. |
- Stedt, Kristoffer, 1991, et al.
(author)
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Determination of nitrogen content in Ulva fenestrata by color image analysis – a rapid and cost-efficient method to estimate nitrogen content in seaweeds
- 2022
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In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
-
Journal article (peer-reviewed)abstract
- There is an increasing interest in the cultivation of seaweeds for food and feed, and the seaweed aquaculture industry is rapidly developing. The nutritional status of the seaweeds is important to ensure a good quality crop. Cost-efficient and straightforward methods for farmers to analyze their crop are essential for the successful development of the industry. In this study, we developed non-destructive, labor- and cost-efficient models to estimate the nitrogen content in the crop seaweed Ulva fenestrata by color image analysis. We quantified tissue nitrogen content and thallus color in sea-farmed seaweed every week throughout a whole cultivation season (15 consecutive weeks) and analyzed data with linear regression models. We showed that color image analysis accurately estimated the nitrogen content in the seaweed (R2 = 0.944 and 0.827 for fresh tissue and dried powder, respectively), and through tenfold cross validation we showed that the developed models were robust and precise. Based on these models, we developed a web-based application that automatically analyzes the nitrogen content of the seaweeds. Furthermore, we produced a color guide that can easily be brought to the farm for onsite crude estimation of seaweeds’ nitrogen content. Our results demonstrate that color can be a powerful tool for seaweed farmers (and researchers) to estimate seaweeds’ nutritional status. We anticipate that similar models can be developed for other commercially interesting seaweed species.
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| 11. |
- Stedt, Kristoffer, 1991, et al.
(author)
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Post-harvest cultivation with seafood process waters improves protein levels of Ulva fenestrata while retaining important food sensory attributes
- 2022
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In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745.
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Journal article (peer-reviewed)abstract
- Seaweed aquaculture can provide the growing human population with a sustainable source of proteins. Sea-based cultivation is an effective method for farming seaweeds on a large scale and can yield high biomass output. However, the quality and biochemical composition of the biomass is seasonally dependent, which limits the harvests to certain periods of the year. Here we show the possibility to extend the sea-based cultivation season of Ulva fenestrata when aiming for high protein levels, by post-harvest treatment in herring production process waters. We harvested U. fenestrata at an optimal period in terms of yield, but suboptimal in terms of protein content. We then cultivated the seaweed in onshore tank systems with the nutrient-rich process waters for 14 days. We monitored biomass yield, crude protein content, amino acid composition, and content of the health concerning metals arsenic, mercury, lead, and cadmium, as well as the sensory properties of the dried biomass. After cultivation in the process waters, biomass yields were 30 - 40% higher (210 – 230 g fresh weight) compared to in seawater (160 g fresh weight). Also, the crude protein and amino acid content increased three to five times in the process waters, reaching 12 - 17 and 15 – 21% dry weight, respectively. The protein enriched biomass followed food graded standards for heavy metal content, and consumption of the biomass does not exceed health based reference points. Additionally, no sensory attributes regarded as negative were found. This rapid, post-harvest treatment can help extend the cultivation season of sea-based seaweed farms, maximizing their output of sustainable proteins.
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| 12. |
- Steinhagen, Sophie, et al.
(author)
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A step towards closing the food-waste gap in novel protein sources: Post-harvest protein boost of the seaweed crop Ulva by herring production tub water
- 2024
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In: Future Foods. - 2666-8335.
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Journal article (peer-reviewed)abstract
- Sea lettuce (Ulva) species have been identified as a future protein source, and post-harvest techniques, including the sustainable integration of liquid food side streams, have been developed to further increase their protein content and commercial market value. This study explores the post-harvest treatment of commercially produced seaweed biomass from large-scale, sea-based cultivations of U. fenestrata with residual water streams emerging from industrial storage of herring – so called herring production tub water (TUB). Growth rates of U. fenestrata were significantly higher in TUB treated seaweeds compared to controls. Further, the crude protein content was 71.26% higher when cultivated in TUB, compared to controls, reaching a crude protein content of 37.37 ± 1.83 % dry weight. Notably, there were no limiting amino acids, nor fish-related allergenic activity in the seaweed biomass. Our study demonstrates a new nutrient loop turning food waste into protein-rich biomass by applying sustainable seaweed cultivation.
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| 13. |
- Steinhagen, Sophie, et al.
(author)
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Closed life-cycle aquaculture of sea lettuce (Ulva fenestrata): performance and biochemical profile differ in early developmental stages
- 2022
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In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
-
Journal article (peer-reviewed)abstract
- Sea lettuce (Ulva) aquaculture has increased the last decade due to high productivity, wide environmental tolerance, and interesting functional and nutritional properties of the crop. Research focus has mainly been on adult biomass production, but knowledge of performance and biochemical content of early developmental stages – which are the basis to any large-scale production - is still limited. The life-history of Ulva alternates between a diploid sporophytic life-stage and a haplontic gametophytic life-stage. Whereas the sporophyte gives raise to recombinant gametophytes through zoids, gametophytes can give raise to parthenogenetically developing, clonal gametes in absence of a mating partner. This study shows that recombinant gametophytes have a faster ontogenetic development, higher growth rate, as well as higher protein, fatty acid, and pigment contents compared to clonal gametophytes of the crop Ulva fenestrata. Nutrient addition is required for a normal development, but temperature and swarmer density have relatively small effects on the hatchery success, relative growth rate and biochemical profile of the juvenile biomass. Our study reveals that the selection of the life-history-phase in novel sea lettuce crop strains could largely contribute to the emerging seaweed aquaculture sector.
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| 14. |
- Steinhagen, Sophie, et al.
(author)
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DNA barcoding of the German green supralittoral zone indicates the distribution and phenotypic plasticity of Blidingia species and reveals Blidingia cornuta sp. nov.
- 2021
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In: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; 70:2, s. 229-245
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Journal article (peer-reviewed)abstract
- In temperate and subarctic regions of the Northern Hemisphere, green algae of the genus Blidingia are a substantial and environment‐shaping component of the upper and mid‐supralittoral zones. However, taxonomic knowledge on these important green algae is still sparse. In the present study, the molecular diversity and distribution of Blidingia species in the German State of Schleswig‐Holstein was examined for the first time, including Baltic Sea and Wadden Sea coasts and the off‐shore island of Helgoland (Heligoland). In total, three entities were delimited by DNA barcoding, and their respective distributions were verified (in decreasing order of abundance: Blidingia marginata, Blidingia cornuta sp. nov. and Blidingia minima). Our molecular data revealed strong taxonomic discrepancies with historical species concepts, which were mainly based on morphological and ontogenetic characters. Using a combination of molecular, morphological and ontogenetic approaches, we were able to disentangle previous mis‐identifications of B. minima and demonstrate that the distribution of B. minima is more restricted than expected within the examined area. Blidingia minima, the type of the genus name Blidingia, is epitypified within this study by material collected at the type locality Helgoland. In contrast with B. minima, B. marginata shows a higher phenotypic plasticity and is more widely distributed in the study area than previously assumed. The third entity, Blidingia cornuta sp. nov., is clearly delimited from other described Blidingia species, due to unique characters in its ontogenetic development and morphology as well as by its tufA and rbcL sequences.
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| 15. |
- Steinhagen, Sophie, et al.
(author)
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Harvest time can affect the optimal yield and quality of sea lettuce (Ulva fenestrata) in a sustainable sea-based cultivation : Seasonal Cultivation of Ulva fenestrata
- 2022
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In: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
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Journal article (peer-reviewed)abstract
- Seaweed biomass is a renewable resource with multiple applications. Sea-based cultivation of seaweeds can provide high biomass yields, low construction, operation, and maintenance costs and could offer an environmentally and economically sustainable alternative to land-based cultivations. The biochemical profile of sea-grown biomass depends on seasonal variation in environmental factors, and the optimization of harvest time is important for the quality of the produced biomass. To identify optimal harvest times of Swedish sea-based cultivated sea lettuce (Ulva fenestrata), this study monitored biomass yield, morphology, chemical composition, fertility, and biofouling at five different harvesting times in April - June 2020. The highest biomass yields (approx. 1.2 kg fw [m rope]-1) were observed in late spring (May). The number and size of holes in the thalli and the amount of fertile and fouled tissue increased with prolonged growth season, which together led to a significant decline in both biomass yield and quality during summer (June). Early spring (April) conditions were optimal for obtaining high fatty acid, protein, biochar, phenolic, and pigment contents in the biomass, whereas carbohydrate and ash content, as well as essential and non-essential elements, increased later in the growth season. Our study results show that the optimal harvest time of sea-based cultivated U. fenestrata depends on the downstream application of the biomass and must be carefully selected to balance yield, quality, and desired biochemical contents to maximize the output of future sea-based algal cultivations in the European Northern Hemisphere.
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| 16. |
- Steinhagen, Sophie, et al.
(author)
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Molecular identification of the ubiquitous green algae Ulva reveals high biodiversity, crypticity, and invasive species in the Atlantic-Baltic Sea region
- 2023
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In: Algal Research. - 2211-9264. ; 73
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Journal article (peer-reviewed)abstract
- Correct species identification is fundamental for assessment and understanding of biodiversity. Erroneous species identification may impede conservation management and may delay detection of invasive species. The ubiquitous green algal genus Ulva is known for its wide environmental tolerance, plastic morphology, occurrence of cryptic species and ambiguous species concepts that hinder clear identification. We used molecular monitoring to assess species diversity and distribution of Ulva along the full Atlantic-Baltic Sea salinity gradient (> 10 000 km). Ulva specimens were collected from Denmark, Finland, Germany, Norway, and Sweden. DNA barcoding analysis of the tufA gene revealed 20 genetic entities in total, of which 11 could be identified to species level (U. californica, U. flexuosa, U. torta, U. linza, U. prolifera, U. fenestrata, U. australis, U. intestinalis, U. compressa, U. gigantea, U. lacinulata). Nine entities (Ulva sp. 1-9; [Ulva capillata]) yielded novel sequence reads that belonged to either unidentified species, species complexes, or singletons. At least 3 of the discovered species (U. australis, U. californica, U. gigantea) are considered non-native and potentially invasive. Furthermore, considerable differences between the observed and the historically estimated species distributions were found. The highest diversity was recorded in the Atlantic and Skagerrak region whereas only two entities were found north-east the Blekinge coast. Our study shows that the species diversity of Ulva in the study area is diverging from previous reports, and that molecular methods are imperative for species identification in this morphologically plastic genus. Furthermore, the presence of non-native species indicates a necessity for further fine-scale monitoring in specific areas to mitigate formation of green tides.
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| 17. |
- Steinhagen, Sophie, et al.
(author)
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Phylogeny and ecology of the green seaweed Ulva
- 2024
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In: Botanica Marina. - 0006-8055 .- 1437-4323.
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Journal article (other academic/artistic)abstract
- Algae of the genus Ulva are of central importance in both applied and basic research, as they present a fascinating mix of biological, ecological, evolutionary, physiological, and genetic research priorities (Blomme et al. 2023; De Clerk et al. 2018; Wichard et al. 2015). Due to their crucial role in coastal ecosystems and their burgeoning commercial use for aquaculture, Ulva spp. have become the focus of many (applied) scientific studies (Bolton et al. 2016; Simon et al. 2022; Steinhagen et al. 2021; Wichard 2023). The cultivation of seaweed for food, feed and useful chemicals has the potential to increase significantly and sustainably. It could provide alternative protein sources, alleviate food shortages and meet increasing demand by utilizing the largely untapped aquatic environment (Barbier et al. 2020; Buck and Shpigel 2023). In any case, the reliable identification of the morphologically variable species and ecotypes of Ulva remains of particular interest and a prerequisite for many applications (Steinhagen et al. 2019).
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| 18. |
- Steinhagen, Sophie, et al.
(author)
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Sustainable large-scale aquaculture of the northern hemisphere sea lettuce, ulva fenestrata, in an off-shore seafarm
- 2021
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 9:6
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Journal article (peer-reviewed)abstract
- The growing world population demands an increase in sustainable resources for biorefining. The opening of new farm grounds and the cultivation of extractive species, such as marine seaweeds, increases worldwide, aiming to provide renewable biomass for food and non-food applications. The potential for European large-scale open ocean farming of the commercial green seaweed crop Ulva is not yet fully realized. Here we conducted manipulative cultivation experiments in order to investigate the effects of hatchery temperature (10 and 15◦C), nutrient addition (PES and 3xPES) and swarmer density (500 and 10,000 swarmers ml−1 ) on the biomass yield and biochemical composition (fatty acid, protein, carbohydrate, pigment and phenolic content) of off-shore cultivated Ulva fenestrata in a Swedish seafarm. High seedling densities were optimal for the growth of this northern hemisphere crop strain and significantly increased the mean biomass yield by ~84% compared to low seedling densities. Variations of nutrients or changes in temperature levels during the hatchery phase were not necessary to increase the subsequent growth in an open-water seafarm, however effects of the factors on the thallus habitus (thallus length/width) were observed. We found no significant effect of the environmental factors applied in the hatchery on the total fatty acid or crude protein content in the off-shore cultivated Ulva. However, low seedling density and low temperature increased the total carbohydrate content and furthermore, high temperature in combination with high nutrient levels decreased the pigment content (chlorophyll a, b, carotenoids). Low temperature in combination with high nutrient levels increased the phenolic content. Our study confirms the successful and sustainable potential for large-scale off-shore cultivation of the Scandinavian crop U. fenestrata. We conclude that high seedling density in the hatchery is most important for increasing the total biomass yield of sea-farmed U. fenestrata, and that changing temperature or addition of nutrients overall does not have a large effect on the biochemical composition. To summarize, our study contributes novel insights into the large-scale off-shore cultivation potential of northern hemisphere U. fenestrata and underpins suitable pre-treatments during the hatchery phase of seedlings to facilitate a successful and cost-efficient large-scale rope cultivation.
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| 19. |
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| 20. |
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| 21. |
- Steinhagen, Sophie, et al.
(author)
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The unheeded existence of the tubular greens: molecular analyses reveal the distribution of a new Ulva species (Ulvophyceae, Chlorophyta), Ulva capillata sp. nov. in the Atlantic-Baltic Sea transect
- 2023
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In: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 35, s. 509-522
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Journal article (peer-reviewed)abstract
- The ubiquitous and species rich genus Ulva comprises entities of green macroalgae with variable morphologies. Ulva species are important from ecological and economic perspectives, but their identification is often problematic. Current knowledge on Ulva diversity has focused mainly on foliose individuals of temperate regions, but genetic and morphological data on tubular species are often insufficient and the species richness is ambiguous due to the lack of molecularly identified type vouchers. Together with a previous study, our study demonstrates that due to the crypticity of tubular entities of the genus Ulva present in the Atlantic-Baltic Sea transect, certain species remained undetected until recently whereas molecular evidence of other historically identified species is missing. An entity which appears to be a relatively frequent species in the Atlantic-Baltic Sea transect and which was probably mis-identified with other species in the past is here described as Ulva capillata sp. nov.. The description is based on molecular identification using tufA and rbcL sequences, and by comparing the species & PRIME; phylogenetic relationships, distribution and range margins in the Atlantic-Baltic Sea transect, as well as on morpho-anatomical characters, and early ontogenetic development. By comparisons with closely related and potentially morphologically overlapping species concepts we were able to identify the uniqueness of U. capillata. Therefore, the description of U. capillata as a new species within the genus Ulva is supported by a combination of molecular, morphological, and ontogentic evidence which confirm their uniqueness in comparison to other species concepts.Furthermore, our results strongly emphasize the importance and necessity to molecularly investigate especially tubular historic type vouchers within the genus Ulva to facilitate a clear species identification to omit continuing with taxonomic confusion and ongoing misapplication of names of e.g. cryptic species concepts within this important green algal genus.
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| 22. |
- Toth, Gunilla B., 1973, et al.
(author)
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Effects of irradiance, temperature, nutrients, and pCO(2) on the growth and biochemical composition of cultivated Ulva fenestrata
- 2020
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In: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 32:5, s. 3243-3254
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Journal article (peer-reviewed)abstract
- Ulva fenestrata is an economically and ecologically important green algal species with a large potential in seaweed aquaculture due to its high productivity, wide environmental tolerance, as well as interesting functional and nutritional properties. Here, we performed a series of manipulative cultivation experiments in order to investigate the effects of irradiance (50, 100, and 160 mu mol photons m(-2) s(-1)), temperature (13 and 18 degrees C), nitrate (< 5, 150, and 500 mu M), phosphate (< 1 and 50 mu M), and pCO(2) (200, 400, and 2500 ppm) on the relative growth rate and biochemical composition (fatty acid, protein, phenolic, ash, and biochar content) in indoor tank cultivation of Swedish U. fenestrata. High irradiance and low temperature were optimal for the growth of this northern hemisphere U. fenestrata strain, but addition of nutrients or changes in pCO(2) levels were not necessary to increase growth. Low irradiance resulted in the highest fatty acid, protein, and phenolic content, while low temperature had a negative effect on the fatty acid content but a positive effect on the protein content. Addition of nutrients (especially nitrate) increased the fatty acid, protein, and phenolic content. High nitrate levels decreased the total ash content of the seaweeds. The char content of the seaweeds did not change in response to any of the manipulated factors, and the only significant effect of changes in pCO(2) was a negative relationship with phenolic content. We conclude that the optimal cultivation conditions for Swedish U. fenestrata are dependent on the desired biomass traits (biomass yield or biochemical composition).
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| 23. |
- Tran, Lan-Anh T., et al.
(author)
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An appraisal ofUlva(Ulvophyceae, Chlorophyta) taxonomy
- 2022
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In: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 34, s. 2689-2703
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Journal article (peer-reviewed)abstract
- The green seaweedUlvais important from ecological and economic perspectives, but the identification of species is often problematic. Here we assessed and discussed different perspectives to establish a stable taxonomic framework forUlva, which will benefit both ecological and applied research. We evaluated (1) the performance of commonly used DNA-barcode markers (ITS rDNA,rbcL, andtufA) using species delimitation methods (PTP and GMYC), (2) the usage of species names in the literature, and (3) the geographic coverage of genetic data to identify poorly sampled regions. Species delimitation employing thetufA gene was the most consistent across methods. Not surprisingly, DNA-based species delimitation was often in disagreement with traditional morphology-based species definitions. Biological species concepts, where tested, proved to be generally narrower than DNA-based species delimitation. Although the use of molecular markers has greatly improved our view ofUlvadiversity, the names associated with DNA sequences in public databases are often unreliable, complicating species identification. Recently, sequencing type materials has considerably reduced the gap between DNA sequence data and Linnaean names, but our knowledge onUlvadiversity remains inadequate, especially in tropical regions. Perspectives forUlvataxonomy include the consistent use of multiple DNA-barcode markers assisted by species delimitation methods, applications of genomic data, and crossing experiments. To arrive at a stable nomenclature, we outline the benefits and shortcomings of adhering to the rules and practices of the International Code of Nomenclature for algae, fungi, and plants, for example, by sequencing name-bearing types and discuss alternative approaches.
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| 24. |
- Trigo, João Pedro, 1995, et al.
(author)
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In vitro digestibility and Caco-2 cell bioavailability of sea lettuce (Ulva fenestrata) proteins extracted using pH-shift processing
- 2021
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In: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 356
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Journal article (peer-reviewed)abstract
- Seaweed is a promising sustainable source of vegan protein as its farming does not require arable land, pesticides/insecticides, nor freshwater supply. However, to be explored as a novel protein source the content and nutritional quality of protein in seaweed need to be improved. We assessed the influence of pH-shift processing on protein degree of hydrolysis (%DH), protein/peptide size distribution, accessibility, and cell bioavailability of Ulva fenestrata proteins after in vitro gastrointestinal digestion. pH-shift processing of Ulva, which concentrated its proteins 3.5-times, significantly improved the %DH from 27.7±2.6% to 35.7±2.1% and the amino acid accessibility from 56.9±4.1% to 72.7±0.6%. Due to the higher amino acid accessibility, the amount of most amino acids transported across the cell monolayers was higher in the protein extracts. Regarding bioavailability, both Ulva and protein extracts were as bioavailable as casein. The protein/peptide molecular size distribution after digestion did not disclose a clear association with bioavailability.
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| 25. |
- Trigo, Joao Pedro, et al.
(author)
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Sensory quality of emulsions prepared with the seaweed Ulva spp. or a derived protein ingredient
- 2024
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In: Journal of Future Foods. - : Beijing Academy of Food Sciences. - 2772-5669. ; 9, s. 10
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Journal article (peer-reviewed)abstract
- The sensory quality of seaweed, whether as a whole biomass or as a protein ingredient, plays a crucial role in its successful commercialization. This study explored the effect of different Ulva species, biomass washing, and pH shift-based protein extraction on the sensory quality of emulsions with 0, 5, and 10 % oil. A trained panel assessed the sensory profile, complemented by analyses of volatile compounds, total ash, and amino acids. Saltiness emerged as the primary distinction between emulsions with unwashed U. linza and U. fenestrata, due to higher ash in the former. Washing U. fenestrata retained sensory qualities despite reduced ash and increased content of the lipid oxidation-marker pentanal. Protein extraction up-concentrated total amino acids 2.9-fold, and yielded emulsions with reduced particle sensation and grassy flavor, while bitterness, sourness, dark color, pentanal, hexanal, and 2-ethylfuran increased. Increased oil content of emulsions lowered their grassy odor which correlated with reduced hexanal content. Overall, these findings can contribute to the development of food products containing seaweed or protein ingredients thereof that match consumer preferences.
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