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Benthic macroalgae must attach firmly to the substrate to prevent being detached and washed away by water motion. The success of the bioadhesion system can be strongly influenced by surface chemistry and so this should be optimized for large-scale cultivation. This is especially important during the early stage of cultivation when the juveniles have little thigmotactic attachment, which is needed to interlock with surface rugosity. Juvenile sporophytes of Saccharina latissima (Phaeophyceae) were directly applied onto polymer films of varied surface composition to determine how the attachment force of the developing holdfast was influenced by surface chemistry. Eight polymer chemistries were examined: polyamide (PA), polyethylene (PE), polyester (PES), polypropylene (PP), polymethylacrylate (PMA), polyvinylalcohol (PVA), polyvinylchloride (PVC) and thermoplastic polyurethane (TPU). The PP and PE were also examined as three grades: commercial grade with additives, pure polymer, or pure polymer following a corona treatment. Additive inclusion and corona significantly reduced the water contact angle (p < 0.0001), indicating an increase in the surface free energy available for bioadhesion. After 6 weeks, the attachment force was greatest on PVA, PA and PVC (0.19–0.33 N), correlating strongly with the achieved biomass (R2 = 0.68). Additives and corona treatment improved holdfast attachment force, particularly corona treated PE (0.28 ± 0.08 N: 0 N without corona). Generally, attachment force appeared greatest on chemistries with a contact angle of 60–75°. These results confirm that the bioadhesion of the phaeophyte holdfast is strongly influenced by the surface free energy of the substrate chosen. Through alteration of the additive composition, attachment could be improved to create bespoke cultivation substrates. Corona treatment is highlighted as a very suitable method for improving holdfast attachment force during cultivation. [ABSTRACT FROM AUTHOR]

Abstract Meiospores of Laminariales macroalgae must select a benthic substratum suitable for their attachment and survival, but also suitable for the development of the sessile sporophyte stage which can grow metres in length. In a controlled four month experiment, meiospores of Saccharina latissima were allowed to settle and develop on twelve different polymer surfaces. Highest meiospore settlement was seen where the attachment force of the developing macroscopic sporophytes was weak (<0.3 N), leading to the eventual detachment of the juveniles before they can grow 100 mm. The sporophyte holdfast cover (%) was strongly related to the biomass achieved (R2 = 0.68) and negatively correlated to the water contact angle (θ w) of the polymer (R2 = 0.45). Yet, meiospore settlement was positively correlated to θ w (R2 = 0.24). The study shows that the selective settlement of the meiospore conflicts with the requirements of the macroscopic sporophyte to attach firmly. It is hypothesised that higher θ w is used by kelp meiospores as a cue for recently disturbed environments, allowing gregarious settlement in areas with reduced interspecific competition. Graphical abstract Unlabelled Image Highlights • Saccharina latissima meiospores favour surfaces with high water contact angles (θ w). • The holdfast bioadhesive of the sporophytes binds weakly to high θ w surfaces. • Juvenile sporophytes are then easy detached once 100 mm, so mortality is high. • Settlement selection can conflict with the needs of the sporophyte to attach firmly. • High θ w , may indicate recently disturbed surfaces without intraspecific competition. [ABSTRACT FROM AUTHOR]

The macroalga Saccharina latissima holds promise as a widespread crop in northern Europe. Currently, seeded lines are cultured for 1–2 months within a hatchery until they become ≥1 mm sporophytes, which are then outplanted to a farm. Textiles are being developed as a cultivation substrate for macroalgae, however due to their large surface area, these need either direct in-situ seeding at the farm or a very short, high turnover hatchery period. Two materials, Kuralon twine and non-woven textile, were seeded using three S. latissima developmental stages: meiospore, gametophyte or juvenile sporophyte. The gametophyte and sporophyte stages were applied using a binder solution to adhere them to the materials. These were outplanted at a seaweed farm in the Sound of Kerrera, UK. After 5 weeks, fronds were significantly larger (45 ± 25 mm) and more abundant (20 ± 8·20 cm −1 ) when seeded with sporophytes over gametophytes or meiospores (8 ± 10 mm and 2 ± 2·20 cm −1 ). This reflects the growth advantage of outplanting juvenile sporophytes, since they are larger and more developed when outplanted. Higher fouling of filamentous algae was seen on the non-woven textile but this did not appear to affect growth. After four months, sporophyte seeded materials had the largest fronds and the greatest fresh mass of 2.1 ± 0.8 kg·20 cm −1 , equivalent to simultaneously deployed hatchery reared twine (2.0 ± 0.1 kg·20 cm −1 ). Gametophyte seeding achieved 0.8 ± 0.6 kg·20 cm −1 while meiospore seeding achieved only 0.1 ± 0.1 kg·20 cm −1 . No difference was found between growth on Kuralon twine or non-woven textile ( p  > 0.05), showing that both are suitable growth substrates. Seeding of juvenile sporophytes onto textile using the binder is demonstrated to be a successful method for the cultivation of S. latissima , and may require only 1% of the hatchery tankage, once optimised. It is expected that this method is transferable to the cultivation of other kelp species. [ABSTRACT FROM AUTHOR]

Seaweeds are receiving increasing attention as third generation biofuels, which do not compete for land or freshwater with agricultural crops and have a high polysaccharide content. Seaweed growth is dependent on the presence of suitable physical and chemical conditions. The selection of cultivation sites with suitable characteristics is therefore essential for the successful establishment of European seaweed mariculture. The growth conditions of the site directly impact the biomass yield and composition of the crop, which in turn control the conversion efficiency of biomass to bioenergy. This review focuses on three European brown phaeophyte kelp species which may be suitable for large-scale offshore cultivation: Laminaria digitata , Saccharina latissima and Sacchoriza polyschides . It describes the known responses of each to a number of important physical and chemical parameters: temperature, salinity, water motion, nutrient concentrations, carbon dioxide/pH, light and ultra-violet radiation. It also reports density effects on their growth rate and what is known concerning the impact of disease and grazing. Conclusions are made on the conditions necessary for the optimal growth of each species for biofuel production. Where conditions are sub-optimal, this review has made recommendations for the most suitable species for a particular set of environmental conditions. [ABSTRACT FROM AUTHOR]

The seasonal chemical profiling of kelp species has historically either being carried out on only a single species or the data dates back over 60 years. This research highlights a detailed chemical composition profile of the four kelp species Laminaria digitata, Laminaria hyperborea, Saccharina latissima and Alaria esculenta over a 14-month period. These kelp species were selected due to their identified potential for cultivation. They were chemically characterised to identify seasonal variations and predict best harvest times. Components of interest included the carbohydrates cellulose, laminarin, alginate and mannitol as well as proteins, ash, metals, moisture, polyphenolics, total carbon and nitrogen content. The highest yields of lamianrin and mannitol coincided with the lowest yields in ash, protein, moisture and polyphenols. The implications of these observations for use of kelp species as a fermentation substrate are discussed. [ABSTRACT FROM AUTHOR]