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The development and recycling of biomass production can partly solve issues of energy, climate change, population growth, food and feed shortages, and environmental pollution. For instance, the use of seaweeds as feedstocks can reduce our reliance on fossil fuel resources, ensure the synthesis of cost-effective and eco-friendly products and biofuels, and develop sustainable biorefinery processes. Nonetheless, seaweeds use in several biorefineries is still in the infancy stage compared to terrestrial plants-based lignocellulosic biomass. Therefore, here we review seaweed biorefineries with focus on seaweed production, economical benefits, and seaweed use as feedstock for anaerobic digestion, biochar, bioplastics, crop health, food, livestock feed, pharmaceuticals and cosmetics. Globally, seaweeds could sequester between 61 and 268 megatonnes of carbon per year, with an average of 173 megatonnes. Nearly 90% of carbon is sequestered by exporting biomass to deep water, while the remaining 10% is buried in coastal sediments. 500 gigatonnes of seaweeds could replace nearly 40% of the current soy protein production. Seaweeds contain valuable bioactive molecules that could be applied as antimicrobial, antioxidant, antiviral, antifungal, anticancer, contraceptive, anti-inflammatory, anti-coagulants, and in other cosmetics and skincare products.

The seaweed hydrocolloid industry, comprising agar, alginate, and carrageenan extracts, continues to grow in the order of 2–3% per year with the Asia-Pacific region increasingly dominating the raw material and manufacturing aspects of the industry. Geographic overviews, also in a historical perspective, of seaweed raw material availability including prices and consumption, manufacturing capacities, and utilizations and sales of extracts is presented. Some current and future industry dynamics, requirements, and changing structures, e.g., Indonesia’s increasingly dominant role within farming of agar and carrageenan-bearing seaweed species, randomly imposing of seaweed harvest restrictions or ban on exports, creation of a global certification standard for seaweed, and supply-demand dynamics for seaweed versus future global population are presented. The industry is increasingly being commoditized and China has become an important and, in many cases, dominant factor within all types of seaweed hydrocolloids and some explanations to this and strategic response by the rest of the industry is also touched upon. Also presented are some areas where the seaweed industry needs help from the scientific community. The main challenge is the ongoing general seaweed deterioration experienced in cultivated species—how are the strains to be improved and revitalized and can cultivation techniques be improved further? There is a general trend towards sustainability and, although seaweed cultivation and harvest can be sustainable, there is interest in the development of greener processes.

A global shortfall in protein supply from capture fisheries has motivated the Malaysian government to revise its aquaculture strategy, focusing on three commodities: seaweed, fish and marine shrimp. However, the performance of the Malaysian aquaculture sector, particularly seaweed production, is poorly documented. This is the first empirical study to undertake a value chain analysis (VCA) of the Malaysian seaweed sector using stakeholder perceptions and secondary data that encompass members of seaweed farming cooperatives (the Semporna Area Farmers’ Association and the governments’ flagship Seaweed Cluster Project). Fieldwork was conducted between April and June 2015 among seaweed stakeholders involved in the value chain using a mixed methods approach—in-depth interviews with key informants, focus group discussions, household surveys, personal observation and secondary data. Qualitative and quantitative data were collected from both upstream (seaweed farming, marketing structure and the Malaysian Good Aquaculture Practices [MyGAP] certification programme) and downstream (seaweed processing) activities involving farmers, intermediaries/middlemen (buyers), processors and officials. Kappaphycus spp. was sold in two forms: (1) dried seaweed to be used as raw materials in carrageenan processing (approximately 90% of total harvest) and (2) fresh seaweed to be used as a source of seedlings (approximately 10% of total harvest). The value chain ended with the carrageenan form, which is exported to international markets. The price of dried seaweed varied according to a combination of seaweed quality, the strength of farmer’s relationships with intermediaries and processors and in response to demand from the carrageenan industry. The prices obtained by Malaysian farmers for dried seaweed and carrageenan remained low, US$ 0.60 and US$ 4.43 per kg, respectively, despite efforts by the government to enhance the value chain by imposing seaweed standards (via MyGAP) for farm management, dried seaweed and semi-refined carrageenan. The VCA was a useful tool to identify and map the market, with the results providing a better understanding of the seaweed sector, which could be helpful in supporting further aquaculture development in Malaysia.

The harvesting of wild seaweeds continues to play an important cultural and socioeconomic role for many coastal communities on Ireland’s Atlantic seaboard. Although Irish waters contain a diverse and substantial benthic seaweed flora, only a few species are exploited commercially. Historically in Ireland, seaweed was commercially used as a raw material in the production of high-volume, low-value commodities such as animal feed and raw material for alginate production. Recently, with increasing acceptance of seaweed as a sea vegetable and its ever-increasing role as a raw material in the cosmetic and pharmaceutical industries, there has been a renewed vigour in the Irish seaweed industry particularly with new entrants into the human nutrition and cosmetic markets producing high-quality, high-value products. Although many of Ireland’s native seaweed species can be sustainably exploited if well managed, the fucoid Ascophyllum nodosum maintained its prominent role in the Irish seaweed industry. The traditional harvesting of A. nodosum in Ireland continues, although the recent introduction of new harvesting techniques, along with the expected expansion of the Irish seaweed cultivation sector, undoubtedly marks a shift in the Irish seaweed seascape. We focus here on the seaweed resources in Irish waters and how the industry has changed in the last 20 years.

Seaweed aquaculture beds (SABs) that support the production of seaweed and their diverse products, cover extensive coastal areas, especially in the Asian-Pacific region, and provide many ecosystem services such as nutrient removal and CO 2 assimilation. The use of SABs in potential carbon dioxide (CO 2 ) mitigation efforts has been proposed with commercial seaweed production in China, India, Indonesia, Japan, Malaysia, Philippines, Republic of Korea, Thailand, and Vietnam, and is at a nascent stage in Australia and New Zealand. We attempted to consider the total annual potential of SABs to drawdown and fix anthropogenic CO 2 . In the last decade, seaweed production has increased tremendously in the Asian-Pacific region. In 2014, the total annual production of Asian-Pacific SABs surpassed 2.61 × 10 6  t dw. Total carbon accumulated annually was more than 0.78 × 10 6  t y −1 , equivalent to over 2.87 × 10 6  t CO 2 y −1 . By increasing the area available for SABs, biomass production, carbon accumulation, and CO 2 drawdown can be enhanced. The conversion of biomass to biofuel can reduce the use of fossil fuels and provide additional mitigation of CO 2 emissions. Contributions of seaweeds as carbon donors to other ecosystems could be significant in global carbon sequestration. The ongoing development of SABs would not only ensure that Asian-Pacific countries will remain leaders in the global seaweed industry but may also provide an added dimension of helping to mitigate the problem of excessive CO 2 emissions.

Palmaria palmata is a highly nutritious seaweed and a prime candidate for developing sustainable aquaculture of human foodstuff in the North Atlantic, but it faces challenges due to high prices and quality inconsistencies. The present study evaluated the use of hydrogen peroxide (H 2 O 2 ) treatment to consistently enhance the antioxidant capacity of this species. Medium-term (3–7 days), moderate (0.1-1 mM) treatment led to increased phenolic content and antioxidant activity, up to 2.2- and 5.4-fold baseline values, respectively. Proteomics analyses were performed to compare in vitro results to abundances of specific proteins. Increases in antioxidant power were tied to a decrease in growth-related proteins; but were not positively correlated to any specific protein group. These results suggest a medium-term, phenolic-driven response. Additional benefits of H 2 O 2 treatment, including its potential for biofouling mitigation, may make this approach highly valuable for improving the quality and consistency of P. palmata and enhancing its valorisation as a functional food and commercial viability.

Seaweeds are well-known for their exceptional capacity to accumulate essential minerals and trace elements needed for human nutrition, although their levels are commonly very variable depending on their morphological features, environmental conditions, and geographic location. Despite this variability, accumulation of Mg, and especially Fe, seems to be prevalent in Chlorophyta, while Rhodophyta and Phaeophyta accumulate higher concentrations of Mn and I, respectively. Both red and brown seaweeds also tend to accumulate higher concentrations of Na, K, and Zn than green seaweeds. Their valuable mineral content grants them great potential for application in the food industry as new ingredients for the development of numerous functional food products. Indeed, many studies have already shown that seaweeds can be used as NaCl replacers in common foods while increasing their content in elements that are oftentimes deficient in European population. In turn, high concentrations of some elements, such as I, need to be carefully addressed when evaluating seaweed consumption, since excessive intake of this element was proven to have negative impacts on health. In this regard, studies point out that although very bioaccessible, I bioavailability seems to be low, contrarily to other elements, such as Na, K, and Fe. Another weakness of seaweed consumption is their capacity to accumulate several toxic metals, which can pose some health risks. Therefore, considering the current great expansion of seaweed consumption by the Western population, specific regulations on this subject should be laid down. This review presents an overview of the mineral content of prevalent edible European macroalgae, highlighting the main factors interfering in their accumulation. Furthermore, the impact of using these marine vegetables as functional ingredients or NaCl replacers in foods will be discussed. Finally, the relationship between macroalgae’s toxic metals content and the lack of European legislation to regulate them will be addressed.

Metabolites exuded by primary producers comprise a significant fraction of marine dissolved organic matter, a poorly characterized, heterogenous mixture that dictates microbial metabolism and biogeochemical cycling. We present a foundational untargeted molecular analysis of exudates released by coral reef primary producers using liquid chromatography–tandem mass spectrometry to examine compounds produced by two coral species and three types of algae (macroalgae, turfing microalgae, and crustose coralline algae [CCA]) from Mo’orea, French Polynesia. Of 10,568 distinct ion features recovered from reef and mesocosm waters, 1,667 were exuded by producers; the majority (86%) were organism specific, reflecting a clear divide between coral and algal exometabolomes. These data allowed us to examine two tenets of coral reef ecology at the molecular level. First, stoichiometric analyses show a significantly reduced nominal carbon oxidation state of algal exometabolites than coral exometabolites, illustrating one ecological mechanism by which algal phase shifts engender fundamental changes in the biogeochemistry of reef biomes. Second, coral and algal exometabolomes were differentially enriched in organic macronutrients, revealing a mechanism for reef nutrientrecycling. Coral exometabolomes were enriched in diverse sources of nitrogen and phosphorus, including tyrosine derivatives, oleoyltaurines, and acyl carnitines. Exometabolites of CCA and turf algae were significantly enriched in nitrogen with distinct signals from polyketide macrolactams and alkaloids, respectively. Macroalgal exometabolomes were dominated by nonnitrogenous compounds, including diverse prenol lipids and steroids. This study provides molecular-level insights into biogeochemical cycling on coral reefs and illustrates how changing benthic cover on reefs influences reef water chemistry with implications for microbial metabolism.

Eukaryotic hosts are associated with microbial communities that are critical to their function. Microbiota manipulation using beneficial microorganisms, for example, in the form of animal probiotics or plant growth-promoting microorganisms (PGPMs), can enhance host performance and health. Recently, seaweed beneficial microorganisms (SBMs) have been identified that promote the growth and development and/or improve disease resistance of seaweeds. This knowledge coincides with global initiatives seeking to expand and intensify seaweed aquaculture. Here, we provide a pathway with the potential to improve commercial cultivation of seaweeds through microbiota manipulation, highlighting that seaweed restoration practices can also benefit from further understanding SBMs and their modes of action. The challenges and opportunities of different approaches to identify and apply SBMs to seaweed aquaculture are discussed. Microbiota manipulation has been used to improve the health and performance of several eukaryotes (e.g., humans, agricultural plants, and aquaculture animals), yet until recently remained unexplored for seaweeds.Seaweed cultivation is the largest aquaculture industry by volume and is rapidly expanding. Technological innovations are needed to improve productivity and meet future global demands.Bacteria are known to promote growth, assist reproduction, and improve disease resistance in seaweeds.Knowledge of seaweed–bacterial symbioses has recently been applied to manipulate host microbiota with demonstrated benefits to seaweeds at the laboratory scale. This provides a realistic and practical opportunity to use these at the scale required for seaweed aquaculture and environmental restoration.