Spatial claims concerning the rapidly growing European offshore wind sector give rise to various ideas for the multi-use application of wind farms. Seaweed is considered a promising feedstock for food and feed that could be produced at offshore wind farms. Concerns about risks resulting in liability claims and insurance premiums are often seen as show-stoppers to multi-use at offshore wind farms. In this study, key environmental risks of seaweed cultivation at offshore wind farms, identified through literature review, are characterized based on stakeholder consultation. The current approach to risk governance is evaluated to assess how it can handle the uncertain, complex, and/or ambiguous risks of multi-use. It is concluded that current risk governance for multi-use is poorly equipped to deal with the systemic nature of risks. Risk governance should be a joint effort of governments and private regulators. It can improve if it is based on an adaptive framework for risk assessment that can deal with complex, systemic risks. Furthermore, it should be flexible and inclusive, i.e., open to new incoming information and stakeholder input, and taking into account and communicate about the different stakes and values of the various parties involved. The importance of communication and inclusion must be recognized, which promotes participation of concerned stakeholders.
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Large-scale Gracilaria cultivation can be an effective means of improving water quality and promoting a more sustainable mariculture industry in China. In tests, the seaweed Gracilaria lemaneiformis provided several beneficial functions. It was very effective in decreasing nitrogen and phosphorus loadings. The seaweed was also able to inhibit the growth of some microalgae and may increase dissolved oxygen in the water column.
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The seaweeds are a diverse group of large marine macroalgae that are as important to the marine world as land plants are to our terrestrial world. Seaweeds were the precursors to land plants, and like land plants, they are critical primary producers, forming living links between the inorganic and the organic world, using photosynthesis to convert CO2 and nutrients into living biomass. These primary producers support and encourage other marine life through the production of oxygen, contribution to marine food webs, and by providing structure and habitat for refuge, breeding, and nursery grounds for fish and invertebrates. Seaweeds are an important resource for humans. Coastal peoples have always utilized seaweeds for food, minerals, medicine, fertilizer and fodder, and these sea-plants continue to provide for an everincreasing world population. A multi-billion dollar industry worldwide, seaweeds are consumed as nutritious sea vegetables, processed to extract valuable phycocolloids including agar, carrageenan, and alginate, and utilized in the agricultural industries for animal fodder or plant fertilizers.
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The aim of the present study was to evaluate the response of grain yield, phosphorus (P) use efficiency (PUE, g yield g–1 P available) and related root traits of wheat and pea to different P availabilities in a high yielding environment (e.g.: yield higher than 10 Mg ha-1 for wheat). Two experiments were conducted in southern Chile. Treatments consisted of the combination of (i) two crops (spring-bred wheat and pea) and (ii) three rates of P fertilization (0 (P0), 100 (P1) and 250 (P2) kg P ha–1). Grain yield of wheat was more sensitive to P deficiency than pea. Wheat showed consistently higher (P < 0.01) PUE than pea, averaging 195 and 125 g yield g–1 P available, respectively. This was principally ascribed to the highest (P < 0.01) P utilization efficiency of wheat (430 vs. 249 g yield g–1 P uptake for wheat and pea, respectively). On the contrary, the P uptake efficiency was slightly different for these crops (0.44 and 0.49 g P g–1 P available, respectively). However, these crops presented different strategies for P acquisition. Wheat had a higher (P < 0.01) soil exploratory capacity than pea, while pea showed a higher (P < 0.01) P uptake per unit of root length than wheat. Wheat showed higher PUE than pea; however, crop differences are ascribed to differences in phosphorus utilization rather than to phosphorus uptake efficiency. This information could contribute to optimized soil P use and improved crop fertilization management.
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The rapidly increasing interest in utilizing seaweeds as sustainable raw material from which multiple high-value bioactive compounds can be recovered, has necessitated the development of new processing methods to achieve this. Brown seaweeds contain a range of bioactive compounds that are of commercial interest, including hydrocolloid and non-hydrocolloid polysaccharides, antioxidant polyphenols and unique pigments. Traditional polysaccharide extraction from brown seaweeds has relied on methods that require harsh chemical processing and sometimes also large amounts of energy and organic solvents. Commercial operation requires high recovery of the targeted compounds on the one hand, but simultaneously also the preservation of biological activity of the products on the other, an objective that is difficult to achieve using conventional methods. In order to address this shortcoming and to move toward more environmentally friendly processing in general, several greener extraction methods are being developed which have lower environmental footprint and sometimes also greater process efficiency, including enzymatic, sub and supercritical fluid, ultrasonic and microwave extraction techniques. This chapter explores these extraction techniques within the context of particularly brown seaweeds and provides an overview of potential advantages compared to conventional technologies. The work further elucidates how certain physiological characteristics of brown seaweeds can impact the processing thereof and looks toward possible future developments within the field of brown seaweed processing.
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In our previous research, the supplementation of Ulva sp. seaweed meal in shrimp feeds as a replacement for fish meal (FM) resulted in growth depression. To understand the factors causing the growth reduction and explore the effects of the seaweed meal as a substitution for soybean meal (SBM), a series of growth trials were conducted in the present study. Shrimp (initial mean weight 0.24, 0.15, and 0.98 g in trials 1–3, respectively) were stocked at 10 shrimp per tank (n = 4) and offered diets for 5 to 6 weeks. In trial 1, FM level was fixed and SBM was replaced using incremental level of the second batch Ulva meal (UM2). Two additional diets were formulated to allow comparison of high inclusion levels of seaweed meal from three batches (UM1–3). Results confirmed reductions in performance as replacement of SBM by Ulva meal was increased. This data also demonstrated significant difference between batches of the Ulva meal with the UM2 producing the poorest results. To elucidate if digestible protein was limiting growth, in trial 2 feeds were formulated on an equal digestible protein basis. At the end of trial 2, shrimp fed with diets containing UM2 exhibited significantly reduced growth performance, survival, and lipid content of whole shrimp body as well as increased feed conversion ratio (FCR) compared to the reference diet. Although performance of shrimp was depressed in the treatments containing UM1 and UM3, this was less than that of trial 2, indicating that protein quality may be part of the problem. Given the level of protein replacement, other components of Ulva meal are likely to be causing poor performance. A third trial was performed to evaluate the potential of the fourth batch Ulva meal (UM4) containing relatively higher protein content than the first three batches. In this trial, the growth, survival, and lipid content of whole shrimp body also decreased as the level of UM4 was increased. To survey possible problems caused by high levels of minerals, the meals and select diets were analyzed for mineral content. Clearly there are shifts in mineral profiles; however, there is no obvious correlation to a mineral. Other possible reasons would include anti-nutrients present in the algae. If Ulva meals are to be used to their full potential, e.g., as a primary protein source, the anti-nutritional components will need to be identified, specific lines of plants with enhanced nutrient value need to be developed and of course processing technologies evaluated to produce a high quality commercial product.
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Marine biorefineries, based on macroalgal (seaweed) feedstocks, could provide sustainable alternative sources of food, energy, and materials. Green macroalgae, with their unique chemical composition, can contribute to marine biorefinery systems associated with a wide range of potential products. This review discusses the challenge of developing industrially relevant and environmentally-friendly green seaweed biorefineries. First, we review potential products from green seaweeds and their co-production, the key element in an integrated biorefinery. Second, we discuss large-scale cultivation, hydrothermal treatments, fermentation, anaerobic digestion, and emerging green solvents, pulsed electric field, microwave, and ultrasound processing technologies. Finally, we analyse the main polysaccharides in green seaweeds: sulfated polysaccharides, starch, and cellulose, as products of a cascading biorefinery, with emphasis on applications and technological challenges. We provide a comprehensive state-of-the-art review of green seaweed as feedstock for the biorefinery, analysing opportunities and challenges in the field.
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The present study was to determine the effects of salinity on the growth and nutrient bioextraction abilities of Gracilaria and Ulva species, and to determine if these seaweeds can be used for nutrient bioextraction under hypo- and / or hyperosmotic conditions. Two Gracilaria species, G. chorda and G. vermiculophylla, and two Ulva species, U. prolifera and U. compressa, were cultured at various salinity conditions (5, 10, 15, 20, 30, 40, and 50 psu) for 3 weeks. Results showed that the growth rates, nutrient uptake, tissue nutrient contents and nutrient removal were significantly affected by salinity and species. All four species were euryhaline with the highest growth rates at 20 psu. Among the four species, U. prolifera, U. compressa, and G. vermiculophylla showed potential to be used for nutrient bioextraction in estuaries and / or land-based fish farms due to their rapid growth, high nutrient uptake, high tissue carbon and nitrogen accumulation and removal capacities.
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Palmaria palmata was integrated with Atlantic halibut Hippoglossus hippoglossus on a commercial farm for one year starting in November, with a temperature range of 0.4 to 19.1°C. The seaweed was grown in nine plastic mesh cages (each 1.25 m3 volume) suspended in a concrete sump tank (46 m3) in each of three recirculating systems. Two tanks received effluent water from tanks stocked with halibut, and the third received ambient seawater serving as a control. Thalli were tumbled by continuous aeration, and held under a constant photoperiod of 16 : 8 (L : D). Palmaria stocking density was 2.95 kg m-3 initially, increasing to 9.85 kg m-3 after a year. Specific growth rate was highest from April to June (8.0 to 9.0°C),1.1% d-1 in the halibut effluent and 0.8% d-1 in the control, but declined to zero or less than zero above 14°C. Total tissue nitrogen of Palmaria in effluent water was 4.2 to 4.4% DW from January to October, whereas tissue N in the control system declined to 3.0-3.6% DW from April to October. Tissue carbon was independent of seawater source at 39.9% DW. Estimated tank space required by Palmaria for 50% removal of the nitrogen excreted by 100 t of halibut during winter is about 29,000 to 38,000 m2, ten times the area required for halibut culture. Fifty percent removal of carbon from the same system requires 7,200 to 9,800 m2 cultivation area. Integration of P. palmata with Atlantic halibut is feasible below 10°C, but is impractical during summer months due to disintegration of thalli associated with reproductive maturation.
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Chlorophyll-a, phycoerythrin, phycocyanin and allophycocyanin of the red alga, Gracilaria edulis, cultured in outdoor tanks under natural light at different depths were estimated. Crop growth rate and pigment contents in relation to varjdng light intensities (depth) were observed. An inverse relationship between pigment content and the light intensity was noted. But growth rate was more at higher light intensities.
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Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.