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Gracilaria verrucosa was successfully cultivated in a pond based aquaculture system at Narakkal. Kerala. India. Daily growth rate of seaweed was found to be maximum (19.22%) during 60 days of introduction. The growth. pigment constituents and the yield of agar were influenced by the environmental parameters. Agar yield and photosynthetic pigments declined in the initial period up to 50 days due to acclimatization of the plants lo new environment which was collected from Chennai, India and introduced in the pond at 'Narakkal. After 60 days, the algae started establishing in the bottom of the pond and an initial harvest of 230.25 kg was harvested after 90 days of culture period. Further regular harvest was made at every 10 days interval yielding 1015 kg of Gverrucosa during the culture period. The agar content ranged between 7-14.8% and bottom sample exhibited better yield of. agar than the plants cultured in the floating raft.

Poor physiological acclimatization to climate change has led to shifts in the distributional ranges of various species and to biodiversity loss. However, evidence also suggests the relevance of non-climatic physical factors, such as light, and biotic factors, which may act in interactive or additive way. We used a mechanistic approach to evaluate the ecophysiological responses of four seaweed species (three dominant intertidal fucoids, Fucus serratus, Ascophyllum nodosum, Bifurcaria bifurcata, and the invasive Sargassum muticum) to different conditions of grazing, light irradiance and ultraviolet (UV) radiation. We performed a large-scale mesocosm experiment with a total of 800 individual thalli of macroalgae. The factorial experimental design included major algal traits, photoacclimation, nutrient stoichiometry and chemical defence as response variables. Few significant effects of the factors acting alone or in combination were observed, suggesting a good capacity for acclimatization in all four species. The significant effects were generally additive and there were no potentially deleterious synergistic effects between factors. Fucus serratus, a species currently undergoing a drastic contraction of its southern distribution limit in Europe, was the most strongly affected species, showing overall lower photosynthetic efficiency than the other species. The growth rate of F. serratus decreased when UV radiation was filtered out, but only in the presence of grazers. Moreover, more individuals of this species tended to reach maturity in the absence of grazers, and the nitrogen content of tissues decreased under full-spectrum light. Only the phlorotannin content of tissues of B. bifurcata and of exudates of A. nodosum, both slow-growing species, were positively affected by respectively removal of UVB radiation and the presence of grazers. The findings for S. muticum, a well-established invasive seaweed across European coasts, suggested similar physiological response of this fast-growing species to different levels of grazing activity and light quality/intensity. As expected, this species grew faster than the other species. Bifurcaria bifurcata and A. nodosum only showed minor effects of light quality and grazing on phlorotannins content, which suggests good resistance of these two long-lived species to the experimental conditions. Mechanistic approaches that are designed to analyse interactive effects of physical and biotic factors provide an understanding of physiological responses of species and help to improve the confidence of predictive distribution models.

Macroalgae, or seaweeds, are multicellular – usually macroscopic – plant-like organisms that generally live attached to rock or other hard substrata in coastal areas. There are about 10,000 species of algae, of which 6,500 are red algae (also named Rhodophyta), 2,000 are brown algae (Phaeophyceae), and 1500 are green algae (Chlorophyta and Charophytes). These three groups have very distinct evolutionary histories and display specific ultrastructural and biochemical features (e.g. pigments). 

Seaweeds are increasingly employed as feedstock around the world, with an annual production of 30Mt for a ~ €8B value. Seaweeds are thus a promising bioresource for the future and demands for high-value seaweed-derived compounds (cosmetics, food) are on the rise in Europe. However, the production of Europe lags behind that of Asian countries despite its large exclusive economic zone, its high seaweed biodiversity and its international leadership in fundamental research on macroalgae.

Drawing on our long-term experience in plant production and domestication in general, as well as on current knowledge of European and worldwide marine ecology, climate and trade, we explore the reasons for this lag, and offer recommendations for improving seaweed cultivation and harvest.

Based on a detailed analysis of current seaweed aquaculture practices, regulations, health benefits and consumer demands, these guidelines aim to foster sustainability and protection of the marine environment. These guidelines also include expert opinions and assessments from the academic, private and associative sectors, based mainly in Europe, but also on other continents. With this wide scope and using a field-based and scientific approach, we have aimed to produce a robust prospective reference document to support policy-makers and the elaboration of future European regulations.