Ocean Multi-use (MU) has gained significant attention as an approach with great potential to promote a more sustainable and space efficient' Blue Economy development. Despite many efforts to implement the multi-use concept into practice, MU still has many practical challenges, which is even more evident outside the European context, where there is significant policy support for MU. This paper aims to elucidate how MU can bolster the local blue economy, particularly within the context of the Global South. The research is based on a case study in southern Brazil, within a traditional fishing community that occupies a marine protected area. A practical analysis of the synergies between community-based tourism, artisanal fishing and conservation was done through interviews with key stakeholders. The main benefits, constraints, opportunities, and risks of MU activities were identified. Results demonstrate the positive impact of MU promoting revenue, environmental education, and cultural and historical attributes. MU has shown great positive impact on social, economic, and environmental aspects within this case study. Key enabling factors that allowed the MU development were horizontal participatory governance and the protagonist of fishers. In terms of existing challenges, the absence of investment in infrastructure, fragmented governance and lack of institutional support was pointed out as the main constraint and limitations to strengthening MU. We argue that MU can be an important strategy for promoting the local blue economy. In the Global South context, the efficacy of MU initiatives appears intricately tied to the participation of local actors in a manner tailored to local contexts and challenges.

Background: With the growing interest in applying fermentation to seaweed biomasses, there is a need for fast and efficient selection of microbial strains that have the ability to 1) acidify quickly, 2) utilize seaweed constituents and c) exhibit some proteolytic activity. The present study aims to provide a fast methodology to screen large bacterial collections for potential applications in optimized seaweed fermentations, as well as investigate and assess the performance of a selected bacterial collection of the National Food Institute Culture Collection (NFICC) in seaweed fermentation. This approach is directed toward high-throughput (HT) methodologies, employing microwell assays for different phenotypical characteristics of lactic acid bacteria isolated from different sources. The overarching aim is the deeper understanding of the selection criteria when designing starter cultures for seaweed fermentation. Results: By employing high-throughput analytical workflows, the screening processing time is minimized, and among the different strains from a well-characterized strain collection, it was possible to distinguish between strong acidifiers and to replicate similar results when the volumes were scaled from 96-well plates to lab-scale fermentations (40 mL) of whole seaweed. Lactiplantibacillus plantarum, Lacticaseibacillus paracasei and, to a lesser extent, Lacticaseibacillus rhamnosus were among the fastest strains to reach the lowest endpoint pH values (< 4.5) in less than 48 h. Although the results regarding proteolytic capacity were not sufficient to prove that the candidates can also provide some flavor generation by the cleavage of proteins, NFICC1746 and NFICC2041 exhibited potential in releasing free alanine, glutamate and asparate as free amino acids. Conclusions: With the described methodology, a large number of terrestrial lactic acid bacteria (LAB) isolates were screened for their performance and possible application for fermentation of brown sewaeeds. With a a fast conversion of sugars to organic acids, three potential new plant-isolated strains from NFICC, specifically Lactiplantibacillus plantarum ssp. argentoratensis (NFICC983), Lacticaseibacillus paracasei (NFICC1746) and Lacticaseibacillus rhamnosus (NFICC2041), were identified as promising candidates for future synthetic consortia aimed at application in bioprocessed seaweed. The combination of such strains will be the future focus to further optimize robust seaweed fermentations.

Deep-ocean seaweed dumping is not an ecological, economical, or ethical answer to climate-change mitigation via carbon “sequestration.” Without sound science and sufficient knowledge on impacts to these fragile ecosystems, it distracts from more rational and effective blue-carbon interventions. We call for a moratorium on sinking seaweeds to deep-ocean ecosystems until its efficacy is established, and there is robust, evidence-based assessment of its environmental, economic, and societal sustainability.

The study examines the governance of low trophic species mariculture (LTM) using Sweden as a case study. LTM, involving species such as seaweeds and mollusks, offers ecosystem services and nutritious foods. Despite its potential to contribute to blue growth and Sustainable Development Goals, LTM development in the EU and OECD countries has stagnated. A framework for mapping governance elements (institutions, structures, and processes) and analyzing governance objective (effective, equitable, responsive, and robust) was combined with surveys addressed to the private entrepreneurs in the sector. Analysis reveals ineffective institutions due to lack of updated legislation and guidance, resulting in ambiguous interpretations. Governance structures include multiple decision-making bodies without a clear coordination agency. Licensing processes were lengthy and costly for the private entrepreneurs, and the outcomes were uncertain. To support Sweden’s blue bioeconomy, LTM governance requires policy integration, clearer direction, coordinated decision-making, and mechanisms for conflict resolution and learning.

This paper offers a comprehensive, analytical, and critically informed overview of the current state of ocean multi-use research. It delves into the origins, trajectory, and driving forces behind this emerging research field, all within the broader context of investigations addressing the management of increasingly diverse and intensifying activities at sea. The Bibliometrix R package is employed to analyze the social, geographical, and conceptual dimensions of multi-use scientific production. The results obtained are then compared to a larger corpus of publications focusing on both multiple-use Marine Protected Areas (MPAs) and Marine Spatial Planning (MSP). Finally, the paper addresses research gaps, with a particular emphasis on the transdisciplinary challenges associated with translating this new marine policy concept into practical implementation and extending its application beyond European seas.

The versatility of microalgae biomass as candidates for various products and bioremediation needs motivates interests towards design and implementation of novel microalgae bioreactors. Conventional open-reactors are reliant on large quantities of sunlight and space while yields are constrained by outdoor environment conditions. Conversely, closed-reactor systems like bubble columns reduces these constrains on microalgae growth while occupying far less space at the expense of high energy demands, notably from lighting systems. A novel patented closed reactor design has recently been proposed that improves the bubble column concept with an efficient and effective lighting system. The present study uses Life Cycle Assessment approach to compare the environmental performance of conventional reactors and the proposed internally luminated novel closed reactor design, expressing impacts per kg biostimulant for the Scenedesmus almeriensis harvest from such units. All performance data was collected from a pilot facility in Almeria, Spain. Urban-industrial symbiosis scenarios are also portrayed in the study using wastewater and incinerator flue gas. Results show that under synthetic nutrient and carbon inputs in Spanish pilot operations, the cumulative energy demand for the novel photobioreactors is similar to conventional vertically-stacked horizon bioreactors but are substantially more demanding than conventional open reactors. However, when leveraging renewable energy sources and the photosynthesis process to consume wastestreams in urban-industrial symbiosis scenarios, the novel photobioreactor was able to achieve up to 80 % improvements in several impact categories e.g. eutrophication and climate change. Impact mitigation credits per kg dwt biomass across all energy scenarios in symbiosis amount to asymptotic to 1.8 kg CO(2)eq and asymptotic to 0.09 kg PO4 eq. This highlights that such closed and internally illuminated photobioreactors can be competitive with conventional reactors, and have potential to harness photosynthesis to reduce environmental burdens in an urban-industrial symbiosis setting. Possible economies of scale and the associated potential gains in efficiencies are further discussed.

The environmental benefits of seaweed cultivation have gained a lot of attention, both in policy strategies and by private companies. Sustainability evaluations of seaweed farming have however focused on a very small part of global production of seaweed - on European cultivations at research and pilot-scales although Asia stands for 99 % of global production with China alone producing 60 %. In this study, we use Life Cycle Assessment (LCA) to evaluate the environmental performance of a 400-hectare Chinese kelp farm with a yearly harvest of 60,000 tons. Primary data from the farm was used to assess impacts up until harvest for the functional unit of 1 ton of fresh-weight kelp. Included in the LCA were impact on climate change, acidification terrestrial and marine eutrophication, and use of land water and energy. In addition, we calculated nutrient uptake. Further, we extracted inventory data of four published LCA studies of farmed kelp and recalculated environmental impacts, applying the same background data and method choices with the aim to compare the effects of scale and cultivation system. The results of the hotspot analysis showed that the plastic ropes and buoys dominated impacts on climate change, freshwater and marine eutrophication, and energy consumption. Consequently, the most effective improvement action was recycling after use. The yearly harvest of the Chinese farm was 1000–4000 times larger than previously evaluated farms compared. Results suggest that streamlined and mature production in the large-scale Chinese kelp farm led to lower electricity and fuel consumption compared to small-scale production, thus placing the Chinese farm with a climate impact of 57.5 kg CO2 eq. per ton fresh-weight kelp on the lower end when comparing the carbon footprint. There was a large variation in carbon footprints, which implies that the kelp cultivation sector has considerable room for optimization.

Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH4-C m−2 day−1, with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.

Researchers have been exploring seaweeds to reduce methane (CH4) emissions from livestock. This study aimed to investigate the potential of a red macroalga, B. hamifera, as an alternative to mitigate CH4 emissions. B. hamifera, harvested from the west coast of Sweden, was used in an in vitro experiment using a fully automated gas production system. The experiment was a randomized complete block design consisting of a 48 h incubation that included a control (grass silage) and B. hamifera inclusions at 2.5%, 5.0%, and 7.5% of grass silage OM mixed with buffered rumen fluid. Predicted in vivo CH4 production and total gas production were estimated by applying a set of models to the gas production data and in vitro fermentation characteristics were evaluated. The results demonstrated that the inclusion of B. hamifera reduced (p = 0.01) predicted in vivo CH4 and total gas productions, and total gas production linearly decreased (p = 0.03) with inclusion of B. hamifera. The molar proportion of propionate increased (p = 0.03) while isovalerate decreased (p = 0.04) with inclusion of B. hamifera. Chemical analyses revealed that B. hamifera had moderate concentrations of polyphenols. The iodine content was low, and there was no detectable bromoform, suggesting quality advantages over Asparagopsis taxiformis. Additionally, B. hamifera exhibited antioxidant activity similar to Resveratrol. The findings of this study indicated that B. hamifera harvested from temperate waters of Sweden possesses capacity to mitigate CH4 in vitro.