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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]

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]