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Aquatic foods hold a unique potential to contribute to a much-needed transformation of food systems thanks to their high nutritional value, cultural significance, and relatively low environmental impact. However, realizing this potential requires a transformative approach to help overcome two grand challenges: sustainably increasing the production of nutritious aquatic foods and ensuring equitable access to these resources. This paper highlights the key recommendations from the White Paper on Challenge 3 ('Sustainably nourish the global population') of the United Nations Decade of Ocean Science for Sustainable Development (hereafter, the Ocean Decade), developed by a group of experts under the Vision 2030 process, on the science needed to support a 'Blue Transformation'. A holistic, interdisciplinary science agenda is proposed, emphasizing strengthened institutional and public–private partnerships, prioritizing the inclusion of small-scale actors, women, and youth, and focusing on delivering science targeted to solve specific challenges. The Ocean Decade provides a platform to catalyse these efforts, fostering a paradigm shift towards inclusive, co-created science. Achieving these goals will enable aquatic food systems to contribute significantly to global food security and the Sustainable Development Goals by 2030. [ABSTRACT FROM AUTHOR]

Molecular studies have contributed to the taxonomy of carrageenan-producing Kappaphycus spp. and Eucheuma denticulatum. However, unresolved species complexes and the lack of standardization in the use of genetic markers impede the identification of specimens and the delineation of a robust taxonomic framework. Here, nine molecular markers (cox1, cox2–3 spacer, cox2, cox3, COB, ITS, psbA, UPA and rbcL) were used to generate a multilocus phylogeny for 113 fresh eucheumatoid samples and four herbarium specimens. Analyses of species delineation and genetic distances confirmed the monophyly of currently accepted taxa. These analyses suggest that clades previously reported as K. striatus KS1 and KS2 are conspecific, and that E. denticulatum EDA 'spinosum' and EDB 'endong/cacing' are also conspecific. The results also unveiled possible new taxa from Hawaii and Indonesia. Each molecular marker and combinations thereof were assessed with regard to species identification, ease of amplification and sequencing, and haplotype characterization. All genetic markers recorded at least 94% success in the amplification and sequencing of fresh specimens, with cox1 being the most phylogenetically informative. Automatic partitioning, phylogenetic and tree-based assessments showed cox1, cox2–3 spacer, cox2 and rbcL were able to correctly identify species while cox1+ rbcL, COB+rbcL, cox2+ rbcL or cox1+ COB+rbcL trees best represented the phylogeny with consistently high nodal support. Among individual markers, cox1 identified the greatest number of haplotypes, while UPA, partial rbcL (750 bp), ITS, cox3 and cox2–3 spacer were able to retrieve information from herbarium specimens of 12–16 years of age. These molecular results provide a basis for a database essential for the taxonomic framework, cultivar development and germplasm conservation of eucheumatoids. Highlights: Mitochondria cox1, cox2–3 spacer, cox2 and plastid rbcL can be used for species identification and cox1 for haplotype detection of eucheumatoids. cox1+rbcL, COB+rbcL, cox2+rbcL or cox1+COB+rbcL are the most cost-effective molecular markers for phylogenetic inference. The most comprehensive up to date multilocus phylogeny of Kappaphycus spp. and Eucheuma denticulatum is presented. [ABSTRACT FROM AUTHOR]

Algal blooms are increasing worldwide, driven by elevated nutrient inputs. However, it is still unknown how tropical benthic algae will respond to heatwaves, which are expected to be more frequent under global warming. In the present study, a multifactorial experiment was carried out to investigate the potential synergistic effects of increased ammonium inputs (25 μM, control at 2.5 μM) and a heatwave (31°C, control at 25°C) on the growth and physiology (e.g., ammonium uptake, nutrient assimilation, photosynthetic performance, and pigment concentrations) of two bloom‐forming algal species, Cladophoropsis sp. and Laurencia sp. Both algae positively responded to elevated ammonium concentrations with higher growth and chlorophyll a and lutein concentrations. Increased temperature was generally a less important driver, interacting with elevated ammonium by decreasing the algaes' %N content and N:P ratios. Interestingly, this stress response was not captured by the photosynthetic yield (Fv/Fm) nor by the carbon assimilation (%C), which increased for both algae at higher temperatures. The negative effects of higher temperature were, however, buffered by nutrient inputs, showing an antagonistic response in the combined treatment for the concentration of VAZ (violaxanthin, antheraxanthin, zeaxanthin) and thalli growth. Ammonium uptake was initially higher for Cladophoropsis sp. and increased for Laurencia sp. over experimental time, showing an acclimation capacity even in a short time interval. This experiment shows that both algae benefited from increased ammonium pulses and were able to overcome the otherwise detrimental stress of increasingly emerging temperature anomalies, which provide them a strong competitive advantage and might support their further expansions in tropical marine systems. [ABSTRACT FROM AUTHOR]

Aquaculture is still in early development in Madagascar and Tanzania, while in Indonesia, aquaculture has a long history. In Madagascar, villagers are farming seaweed and sea cucumbers, as part of small-scale community-based aquaculture (CBA). They followed a contractual model between a private farming company and farmers. Local non-governmental organisations (NGOs) and public institutions in Madagascar jointly strive to reverse the trend of ongoing anthropogenic coastal degradation. In Tanzania, the cultivation of red seaweeds has been established for over 30 years, with declining production attributed to climate change. While shrimp farming still involves, to some extent, clearing of mangroves in Tanzania, seaweed culture has only mild impact on coastal ecosystems. Farming areas provide shelter and habitat for juvenile fish, crabs and other organisms. Therefore, NGOs ask for support to improve culture methods. Various problems and shortcomings in Indonesia have been clearly identified, including issues related to new aquaculture areas, pollutants, emerging diseases, insufficient broodstock and fry supply, as well as a lack of technology and manpower. To address these challenges and ensure the growth of aquaculture production, the government has implemented national policies and established training and broodstock centers throughout the country. In Madagascar, the CBA programme stands out as a success story and can serve as a template for other coastal regions and countries. In Tanzania, the adoption of CBA model for co-culture could be the future. In Indonesia, due to a very long coastlines and complicated legislation, IMTA seems to be particularly suitable, as successfully tested in model regions. [ABSTRACT FROM AUTHOR]

The lack of top‐down control on Tripneustes gratilla, a sea urchin commonly known to graze on seagrass, and the bottom‐up control of its feeding preference, led to the overgrazing of seagrass meadows of the species Thalassodendron ciliatum in Changuu Island (Zanzibar Archipelago). The impact of overgrazing on seagrasses was assessed by mapping the presence of grazed versus non‐grazed seagrass patches in the study site, while the top‐down control on T. gratilla was assessed by measuring the abundance of its fish predators. The feeding preference and distribution of T. gratilla were characterized by calculating the electivity indexes for each seagrass species and measuring sea urchin density, respectively. Approximately half of the patches of T. ciliatum were overgrazed, while predatory fishes of T. gratilla were absent from the site. The Vanderploeg and Scavia's Relativized Electivity Index indicated that T. gratilla had a feeding preference for T. ciliatum, which was also supported by higher urchin densities within T. ciliatum dominated patches. Bottom‐up control of grazing activity was observed by quantifying and analyzing morphological, nutritional, and the chemical defense traits of the seagrass in relation to feeding preference and urchin density. Feeding was positively correlated to the seagrass tissue C:P ratio (ρ = 0.9), whereas urchin density showed no correlations. The bottom‐up control of the feeding preference and agglomeration of T. gratilla in T. ciliatum meadows, together with the lack of evidence of substantial top‐down control and the long recovery time of T. ciliatum led to the overgrazing of this species at this site. Overgrazing, therefore, was shown to be the result of multiple factors ranging from the traits of the seagrass and feeding preference of T. gratilla, to the abundance of predators in this area. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Seaweed cultivation is the fastest‐growing aquaculture sector, with a demonstrable potential to drive development in some of the poorest coastal populations worldwide. However, sustainable exploitation, fair access and equitable benefits from marine genetic resources, such as seaweeds have yet to be fully realised. Patchy fundamental knowledge on the genetic diversity and metabolic potential of algae limits their exploitation; scant practical skills and low investment in breeding restricts germplasm availability and the Nagoya protocol has only partially remediated insufficient governance. Further developments and the addressing of knowledge gaps in relation to biosecurity, breeders' rights and conservation of genetic resources are needed for progress. Summary: We review how seaweed genetic resources are currently used in aquaculture, in relation to the diversification and rapidly increasing use of marine resources. Using a revealing case‐study, we summarise the potential for positive societal change, underpinned by the cultivation of eucheumatoid carrageenophytes (species of the red algal genera Eucheuma and Kappaphycus), an activity which has been successfully initiated in many tropical countries to support their economic development. We also review the challenges currently faced by this industry and identify potential threats to the seaweed cultivation sector. Accordingly, we suggest new directions to support the continued development of an economically resilient and environmentally sustainable industry based on the utilisation of genetic resources. [ABSTRACT FROM AUTHOR]

Tanzania is endowed with a rich biodiversity of seaweed species that grow naturally in its oligotrophic waters of the Western Indian Ocean. Most of these species are unexploited. Only two red seaweeds Eucheuma and Kappaphycus have been studied for commercial farming and the industrial production is based on these species. Another genus of red seaweed, Gracilaria, has been studied and experimented upon for potential farming while others such as the green Ulva, the red Hypnea and the brown Sargassum have been mentioned as potential species for farming. Farming technology used to cultivate the two commercial species is the shallow water off-bottom technology which is badly affected by the increase in surface seawater temperatures (climate change), causing massive die-backs and decreased seaweed production. Some deeper-water farming technologies have been developed but only tubular nets show promise and have been piloted. A number of opportunities exist in seaweed farming, which can be used to advance the industry. The future of the seaweed industry in Tanzania will depend on using the existing opportunities, including utilising the seaweed species already studied, exploring the potential of other seaweed species for farming, development of deeper-water farming technologies, added-value, and ensuring availability of good quality seed material. [ABSTRACT FROM AUTHOR]

Since 2011, seaweed farmers and traders have experienced serious decreased production and income. This study identifies some causes of the seaweed die-off of Eucheuma denticulatum (commonly known as spinosum) and Kappaphycus striatum and K. alvarezii (both commonly known as cottonii) observed in the farming areas of Unguja and Pemba (Zanzibar archipelago). It also makes short- and long-term recommendations to protect the farming ecosystem environment, control (prevention and mitigation) of ice-ice disease and epiphyte infestation, and boost the seaweed industry in the island. Die-offs are mainly caused by a severe case of epiphyte infestation coupled with a high incidence of ice-ice disease, which has long been observed by farmers to intensify during the hot-dry season and diminish during the wet season. High temperature in the farming sites (29.5-35.5 °C) is determined as one of the main triggers of the ice-ice occurrence as well as the bloom of epiphyte infestation. Another factor is high light intensity/irradiance. As seaweed farming in Zanzibar is mainly done in shallow intertidal lagoons, seaweeds are almost in direct contact with the bottom substrate during low tides and hence exposed to higher levels of temperature and light intensity. This combination predisposes seaweed to opportunistic pathogens, manifesting the thalli whitening popularly called ice-ice disease. Bacterial infection leads to softening of the thalli and to their eventual fragmentation. These infestations and diseases are a continuing threat to the commercially farmed eucheumoids and makes seaweed production in Zanzibar to be highly season dependent from what used to be a continuous year-round of plant-harvest-plant cycle done every 30-45 days, providing a steady income to seaweed farmers who are 90 percent women. The study recommends short-term measures and long-term strategies that include: (i) implementing strict quarantine procedures; (ii) transferring the farming of E. denticulatum and K. striatum to deeper waters (2-5 m) using longlines or raft method where practical; (iii) using a "freshwater shock" or a commercially available anti-fouling agent to eliminate epiphytes if lagoon farming is continued during the hot-dry season; (iv) promoting the farming of a variety of E. denticulatum called million-million; (v) improving the genetic stock with alternative local strains; (vi) promoting income-generating activities for farmers, such as value addition using harvested seaweed; (vii) developing multitrophic sustainable aquaculture by integrating seaweed aquaculture with other high-value species; and (viii) creating livelihood opportunities other than farming by exploring the potential of harvesting/farming other seaweeds with other uses that are abundant in Zanzibar. [ABSTRACT FROM AUTHOR]

In most developing countries, the majority of people involved with seaweed farming are women. Their immense contribution to the industry has been widely demonstrated and evaluated in successful examples/case studies. These ‘seaweed women’ have made significant advances in the sustainability of seaweed farming for more than four decades and their dedication, patience and resilience illustrate tenacity in the face of crises. The roles of women are complex, including hands-on farming activities as well as small-scale processing to produce value-added products based on the seaweed biomass cultivated. We detail the role of women in seaweed aquaculture in the Western Indian Ocean (WIO, including Africa and India) and South-East Asia. In Africa, there are significantly more women than men employed, and their roles are more varied, whilst in South-East Asia, men and women are involved in almost equal numbers at the various levels of the seaweed industry. Seaweed farming in SE Asia is carried out by family-owned businesses which involve all working age members of the family, be it nuclear or extended family members, as compared with the WIO region. Five case studies of individual women are provided to show how they have been and continue to be the pillars of the seaweed farming industry. Economic gains from seaweed farming in both regions have provided positive and favourable changes in the quality of life (e.g. food, shelter, clothing, health care and social acceptance) of the family members involved. The case studies point to the commitment of women as the driving force of the seaweed industry, adding value to seaweeds, especially in the WIO. With such women spearheading the seaweed industry, the benefits will continue to be shared with whole families as well as other community members, as mothers are strong anchors of the families in many communities in developing countries. [ABSTRACT FROM PUBLISHER]

Mangroves provide multiple benefits, from carbon storage and shoreline protection to food and energy for natural resource-dependent coastal communities. However, they are coming under increasing pressure from climate change, coastal development, and aquaculture. There is increasing need to better understand the changes mangroves face and whether these changes differ or are similar in different parts of the world. Using a multiple case study approach, focused on Vietnam, Zanzibar, and Brazil, this research analyzed the drivers, pressures, states, impacts, and responses (DPSIR) of mangrove systems. A qualitative content analysis was used on a purposively sampled document set for each country to identify and collate evidence under each of the DPSIR categories. Population growth and changing political and economic processes were key drivers across the three countries, leading to land use change and declining states of mangroves. This had an impact on the delivery of regulatory and provisioning ecosystem services from mangroves and on the welfare of coastal communities. Responses have been predominantly regulatory and aim to improve mangrove states, but without always considering ecosystem services or the consequences for welfare. The issue of scale emerged as a critical factor with drivers, pressures, impacts, and responses operating at different levels (from international to local), with consequences for response effectiveness. [ABSTRACT FROM AUTHOR]

Commercially valuable sea cucumbers are potential co-culture species in tropical lagoon environments, where they may be integrated into established aquaculture areas used for seaweed farming. In the current study, wild-caught juvenile sea cucumbers, Holothuria scabra, and red seaweed Kappaphycus striatum were co-cultured on Zanzibar, United Republic of Tanzania. Sea cucumbers (97 g ± 31 SD, n = 52) were cultured in mesh enclosures at initial cage stocking densities of 124 ± 21 SD and 218 ± 16 SD g m−2 under seaweed culture lines. Over 83 days, individual growth rate (1.6 g d−1 ± 0.2 SD) of sea cucumbers at low stocking density was significantly higher (χ2 = 8.292, d.f. = 1, P = 0.004) than at high-stocking density (0.9 g d−1 ± 0.1 SD). Seaweed individual growth rates [6.27 (±0.3 SE) g d−1] were highest in co-culture with sea cucumber at low density but did not differ significantly from high sea cucumber density or seaweed monoculture treatments (χ2 = 3.0885, d.f. = 2, P = 0.2135). Seaweed growth varied significantly (χ2 = 35.6, d.f. = 2, P < 0.0001) with sampling period, with the final sampling period resulting in the highest growth rate. Growth performance for seaweed and sea cucumbers (χ2 = 3.089, d.f. = 2, P = 0.21 and χ2 = 0.08, d.f. = 1, P = 0.777 respectively), did not differ significantly between monoculture and co-culture treatments, yet growth in co-culture was comparable with that reported for existing commercial monoculture. Results indicate H. scabra is a highly viable candidate species for lagoon co-culture with seaweed. Co-culture offers a more efficient use of limited coastal space over monoculture and is recommended as a potential coastal livelihood option for lagoon farmers in tropical regions. [ABSTRACT FROM AUTHOR]

The farming of the red seaweedKappaphycus alvareziiand related species as raw material for the hydrocolloid carrageenan rapidly spread from the Philippines in the late 1960s to Indonesia, Tanzania, and other tropical countries around the world. Although numerous studies have documented positive socioeconomic impacts for seaweed farming, factors such as diseases and distance to export markets have led to an uneven development of the industry. Using standard budgeting techniques, this study adapted production and market data from a FAO-led global review of seaweed farming to develop comparative enterprise budgets for eight farming systems in six countries (Indonesia, the Philippines, Tanzania, India, Solomon Islands, and Mexico). Although the basic technology package is the same across countries, the study revealed large differences in the economic performance of systems due to wide variations in farm prices and the scale of operations. Although seaweed farming is a suitable activity for small-scale producers, a minimum of 2,000 m of cultures lines are still necessary to ensure adequate economic returns. Greater farming plots may be needed if farm prices are well below the average farm prices paid in Indonesia and the Philippines. Policy recommendations are made to improve the economic potential of underperforming systems. [ABSTRACT FROM PUBLISHER]

The seaweed Ulva lactuca L. was spray cultured by mariculture effluents in a mattress-like layer, held in air on slanted boards by plastic netting. Air-agitated seaweed suspension tanks were the reference. Growth rate, yield, and ammonia-N removal rate were 11.8% · d−1, 171 g fresh weight (fwt) · m−2 · d−1, and 5 g N · m−2 · d−1, respectively, by the spray-cultured U. lactuca, and 16.9% · d−1, 283 g fwt · m−2 · d−1, and 7 g N · m−2 · d−1, respectively, by the tank U. lactuca. Biomass protein content was similar in both treatments. Dissolved oxygen in the fishpond effluent water was raised by >3 mg · L−1 and pH by up to half a unit, upon passage through both culture systems. The data suggest that spray-irrigation culture of U. lactuca in this simple green-mattress-like system supplies the seaweed all it needs to grow and biofilter at rates close to those in standard air-agitated tank culture. [ABSTRACT FROM AUTHOR]

The small-fisheries social-ecological system in the western Indian Ocean (WIO) represents a typical social-ecological trap setting where very poor natural resources dependent coastal communities face local and global threats and engage in unsustainable practices of exploiting limited resources. Community-based aquaculture (CBA) has been implemented as an important alternative or supplementary income generating activity for minimizing the overdependence on marine natural resources and promoting biodiversity conservation. Despite its proliferation throughout the WIO region in recent decades, little is known about the degree to which CBA activities have contributed to achieving the objectives of breaking the cycle of poverty and environmental degradation and promoting community development and biodiversity conservation. In order to improve understanding of common challenges and to generate recommendations for best practice, we assessed the most common CBA activities practiced in the region through literature review and workshop discussion involving practitioners and key stakeholders. Findings indicated that despite favorable environmental conditions for various CBA practices, the sector remains underdeveloped, with few activities delivering the intended benefits for coastal livelihoods or conservation. Constraints included a shortage of seed and feed supplies, low investment, limited technical capacity and skills, insufficient political support, and lack of a clear strategy for aquaculture development. These are compounded by a lack of engagement of local stakeholders, with decision making often dominated by donors, development agencies, and private sector partners. Many of the region's CBA projects are designed along unrealistically short time frames, driven by donors rather than entrepreneurs, and so are unable to achieve financial sustainability, which limits the opportunity for capacity building and longer-term development. There is little or no monitoring on ecological and socioeconomic impacts. Except for a few isolated cases, links between CBA and marine conservation outcomes have rarely been demonstrated. Realizing the potential of CBA in contributing toward food security in the WIO will necessitate concerted investment and capacity strengthening to overcome these systemic challenges in the sector. Lessons herein offer managers, scientists, and policy advisors guidance on addressing the challenges faced in building strategic development initiatives around aquaculture in developing countries. [ABSTRACT FROM AUTHOR]