Seaweeds play essential ecological and biogeochemical roles and support important industrial applications. Sustaining natural populations of seaweeds under climate change while simultaneously putting seaweeds to use in climate solutions requires that we weave together disparate lines of inquiry—the ecological and the industrial—to create a more holistic perspective and integrated research agenda. Innovation in the use of seaweeds must be more than aspirational—it requires evidence of effectiveness in the short term, and a promise to sustain nature and people in the long term.
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Alaria esculenta is a brown seaweed with a great potential for biomass production due to its high productivity and high content of carbohydrates, proteins, vitamins, minerals and bioactive compounds like phlorotannins and pigments. Alaria cultivation is performed either by collection and settlement of zoospores on ropes to develop seedlings, or by production of the seedlings from vegetative gametophyte cultures. Contrary to the zoospore technique, the use of gametophyte cultures has the potential to provide a constant, year-round supply of seedlings. There is a need for optimizing the production methods such as the maintenance of the gametophyte cultures, gametogenesis, seeding process and deployment time. The purpose of this dissertation is to optimize several parameters involved in Alaria cultivation using vegetative gametophytes and provide qualitative and quantitative information related to kelp phlorotannins. Optical density and in vivo fluorescence were evaluated as an alternative method to estimate gametophyte biomass. Both methods showed linearity with the dry weight. The cultures were also supplemented with a possible growth enhancer and the effect evaluated on the cultures, however no growth improvements were noticed on these cultures. When the seedlings production is initiated, the fertility of vegetative gametophytes needs to be switched on. The fertility induction was evaluated with three different photoperiod regimes under white light, where the best performance was accomplished by 23 hours light over 8 days. The seeding density is the next step to optimize seaweed industry. Higher and lower densities bring several disadvantages to the development of the sporophytes. Thus, four densities of fertile gametophyte cultures were tested, where a density per dry weight of 0.8 mg/mL produced the most acceptable number of sporophytes on the twines. For the estimation of sporophyte growth, manual measurements, such as sporophytes counting and length measurement, are extremely time-consuming methods. An alternative method based on image analysis was tested to estimate the percentage of growth of the seedlings and compared with the manual method. The image analysis method was shown to have a good relationship with the sporophyte measurements, bringing a faster and easier way to estimate the seedlings growth. A. esculenta and S. latissima could represent a viable source of phlorotannins (PHL) due to the fast and efficient grow of these species. The juvenile stages of these species had an average of 4.11 and 3.08 mg PHL/g algae, respectively. It was also observed that the phlorotannin content in the Alaria gametophytes increased during fertilization. Two forms of phloroglucinol were documented in both species but due to the lack of studies related with the phlorotannin characterization of these species no more compounds were identified.
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An experiment was conducted in earthen ponds at the Asian Institute of Technology, Thailand to determine different phosphorus fertilizer dose effects on Nile tilapia production, water quality variables, nutrient utilization and cost-benefit under supplemental feeding. Five phosphorus fertil- ization rates were used as treatments e.g. 100%, 75%, 50%, 25% and 0% of 7 kg P ha week1. Nitrogen fertilization rate was fixed at 28 kg N ha week1 for all the treatments. Sex-reversed Nile tilapia were stocked at 3 fish m2, and 30% CP floating feed fed at 50% satiation feeding rate. Nutrient budget showed higher phosphorus fertil- izer input resulted in higher phosphorus sink in the sediment. Mean weight, mean weight gain, daily weight gain and net yield were not signifi- cantly different among treatments (P > 0.05). Total Kjeldahl nitrogen, total phosphorus and sol- uble reactive phosphorus were significantly differ- ent among treatments. Economic analysis showed phosphorus fertilization resulted in positive net returns. Though the gross income was not affected by different fertilization rates, significantly lowest cost was found in the treatment using 25% phos- phorus fertilizer. It can be concluded from the research that 25% phosphorus fertilization might be used as an alternative strategy of Nile tilapia pond culture in terms of economic return and nutrient loss in sediment.
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India has a long rich bio-diverse coastline that provides livelihood to millions. While traditional aqua farming has helped shape the coastal economy over the years, the country has been rather obtuse in adopting seaweed cultivation, an allied agricultural sector that holds immense prospects for the nation’s economy.
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This overview report addresses opportunities for the development of the Pacific Islands’ mariculture sector in general terms. More specific analysis of opportunity in particular
countries is presented in the five accompanying country reports (Cook Islands, Fiji, Papua New Guinea, Republic of the Marshall Islands and Solomon Islands).
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Seaweed aquaculture is a relatively young industry in the United States compared to Asian countries. Early attempts at seaweed aquaculture in California, Washington State, New York and the Gulf of Maine in the 1980s and 1990s did not result in commercial production but provided important lessons. Since 2010, commercial cultivation of kelp (Saccharina latissima, Laminaria digitata, and Alaria esculenta) and other seaweeds (Palmaria palmata and Porphyra umbilicalis) began in the Gulf of Maine and Long Island Sound. Seaweed aquaculture is now a fast-growing maritime industry, especially in New England. If seaweed aquaculture is to maintain its momentum, it is important to (1) emphasise the environmental benefits; (2) domesticate a variety of local species; and (3) diversify seaweed products for food, animal feed, phycocolloids, cosmeceuticals, nutraceuticals, and ultimately biofuels if it becomes economically viable due to the cost of production. The exclusive economic zone (EEZ) of the United States offers opportunities for expansion of seaweed aquaculture in an area greater than the entire land mass of the United States and with limited user conflicts. This study reviews the past and current status of seaweed aquaculture in the United States and discusses potential opportunities and challenges of open-water seaweed aquaculture.
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Quickly reducing methane emissions is an important strategy for meeting 2050 climate targets because of the powerful radiative forcing of methane and its relatively short lifetime, but this strategy is undermined by rapidly rising emissions. Agriculture contributes around 40-46% of global methane emissions, and because of rising food production, these emissions are on a path to increase roughly 40% by 2050. Of these emissions, two-thirds are from enteric methane from ruminant livestock, roughly 20% are from rice, and 7% are from managed manure. Although mitigation efforts for agriculture have received less attention, we set forth a credible scenario to decrease these emissions by 54% relative to otherwise likely emissions in 2050 and by 36% compared to present emission levels. Mitigation opportunities include: (1) increasing the feed efficiency of ruminant livestock; (2) rapid development and deployment of promising enteric methane inhibitors; (3) realizing an “Optimistic Trend Projection” for consumption of ruminant meat, which relies more heavily on alternative sources of animal protein; (4) deployment of at least one basic water level drawdown in flooded rice fields plus better offseason management of residues; (5) broad use of at least one method of reducing methane emissions from manure managed in wet form; and (6) reductions in global food loss and waste. Other innovative ideas are also promising. To achieve this mitigation, we suggest in the near-term an internationally coordinated effort to develop “shovel-ready” projects using known mitigation options but structured to encourage innovation and to improve our understanding of how to reduce emissions further. We also suggest a series of internationally coordinated R&D projects and demonstration projects of promising technologies. One key need is a $100 million initiative to have multi-year tests of promising enteric methane inhibitors in at least 20 world locations, and related technical work to bring them to market.
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The unique chemical composition of seaweeds and their fast growth rates offer many opportunities for biorefining. In this article we argue that cascading biorefinery valorization concepts are viable alternatives to only using seaweeds as carbohydrate sources for the fermentative production of biofuels. However, many challenges remain with respect to use of seaweeds for chemical production, such as the large seasonal variation in the chemical composition of seaweeds.
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These are the opening remarks for the 20th International Seaweed Symposium, held in Ensanada, Mexico in 2010. Professor Thierry Chopin, Pesident of the International Seaweed Association, briefly discusses applications for marine and freshwater macroflaura (algae).
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Saccharina latissima is an economically and ecologically important native kelp. As its limited supply from wild stock cannot meet increasing current and future demands, methods for its cultivation in the ocean need to be developed. This kelp is now beginning to be farmed off the Atlantic coast of Spain using a regular method similar to the “forced cultivation” technique used with Asian kelps (kombu). Its cultivation is also a growing enterprise in other European countries. In this study, the open-sea farming of S. latissima using the transplanting method is tested on a commercial-scale. This cultivation method has not been studied with kelp species outside Asian waters. The tested method includes the following steps: indoor production of seedlings, pre-culture in greenhouse tanks and open-sea cultivation by transplanting young fronds. Results demonstrate that open-sea cultivation using transplanted young fronds is a technically and biologically viable method. The total yield obtained (8.3 kg fresh m−1 rope equivalent to 45.6 ton fresh ha−1 farm) is satisfactory considering the low densities of transplanted fronds (25–30 fronds m−1 rope). Moreover, these values are comparable to those reported in previous cultivations with this species, as well as in the farming of similar kelps. The transplanting method used in conjunction with the regular cultivation method has valuable practical applications for the commercial farming of S. latissima.
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