Macro-algues

SEAWEED RESEARCH

Macro-algae, essential to coastal ecosystems and the carbon cycle, have strong ecological and biotechnological potential. 48 ANR projects have led to major advances in genomic sequencing, understanding responses to climate change, valorizing the bioactive properties of algae, and modeling their proliferation. Governed by specific regulations according to their use (fishing, cultivation, processing), they are part of the blue bioeconomy. Research perspectives aim to develop sustainable cultivation, zero-waste biorefineries, and strengthen innovation in the service of ecological transition and food security.

Claire Hellio UBO and Philippe Potin CNRS, Sb Roscoff

1) Scientific background

Research on macroalgae has experienced significant advancements over the past two decades, driven by the growing recognition of its biological, ecological, biotechnological and economic importance. Seaweeds – including red, green, and brown macroalgae – are primary producers and foundation species, playing vital roles in coastal ecosystems, providing habitat, sequestering carbon, and cycling nutrients (Filbee-Dexter et al, 2024). Their applications span numerous industries, including food, feed and plant biostimulants, cosmetics, pharmaceuticals, and bioplastics. Here, we summarize the state of the art in macroalgae research, highlighting key breakthroughs.

Over the last 20 years, application of modern ‘omic and genetic methods has significantly advanced our understanding of the origin, evolution, and metabolic potential of multicellular algae, as well as their diverse modes of sexual reproduction (Brodie et al., 2017). Genome-enabled studies have revealed the significance of specific transcription factors, small RNAs, epigenetics, and transposable elements in algal plasticity. Linking hypotheses generated from genomic analyses to specific activities and/or phenotypes is facilitating the development of a new range of tools for algal studies and breeding. New generation sequencing methods applied to seaweeds have also accelerated the development of population genetics studies which have provided new knowledge on the genetic structure, diversity and mating systems for numerous species of ecological and/or economic importance.

Significant progress has been made in understanding the physiological responses of seaweeds to climate-induced stressors. Experimental studies and genomic approaches have provided insights into mechanisms of thermal tolerance, acidification resilience, and adaptation to changing salinity. Emerging evidence shows also that their microbiota plays an important role in the seaweed nitrogen fixation, vitamin uptake, development, stress response and reproduction. The concept of holobiont has also been applied to seaweeds which are no longer seen as independent organisms, but fully interacting with their associated microbiomes (Saha et al., 2024).

Considerable progress has been made in understanding the ecological roles of seaweeds, particularly in the context of global change. Concurrently, the impacts of environmental stressors, such as ocean warming, acidification, and pollution, on seaweed resilience and community structure have been extensively studied. Studies have demonstrated their importance as primary producers and their contributions to detrital food chains, influencing coastal productivity and supporting marine biodiversity. Research has also started to decipher the contribution of macroalgal habitats, such as kelp forests or seaweed farming, to blue carbon sequestration (Krause-Jensen & Duarte, 2016; Pessarrodona et al., 2024). Studies have quantified their capacity to capture and store atmospheric CO2 transferred in the ocean. Advances in ecological monitoring and modelling have enhanced the understanding of seaweed biodiversity and the dynamics of their habitats. Remote sensing and GIS technologies have been widely adopted to map seaweed distribution on regional and global scales. Policy frameworks now increasingly recognize the importance of conserving seaweed ecosystems for biodiversity and climate regulation. Research has further elucidated the role of seaweeds in marine food webs and in the context of coastal eutrophication. Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years.

Regarding biotechnological advances, seaweed aquaculture has undergone rapid development, becoming a major focus of research due to its potential for sustainable biomass production. Innovations in cultivation techniques, such as integrated multi-trophic aquaculture (IMTA) systems, aimed to improve productivity and minimize environmental impacts. The discovery and characterization of bioactive compounds in macroalgae have expanded their applications in pharmaceuticals, nutraceuticals, and cosmetics. Compounds such as fucoidans, carrageenans, and phlorotannins have been prove anti-inflammatory, antiviral, and antioxidant properties, leading to potential therapeutic applications and numerous developments of actives for the cosmetic industry. Moreover, seaweeds have gained attention as a renewable resource for bio-solutions in agriculture. Some research has also focused on optimizing fermentation processes to produce bioethanol and biogas from seaweed biomass. Additionally, polysaccharides extracted from seaweeds are being explored as feedstocks for biodegradable plastics or surfactants, offering eco-friendly alternatives to oil-based materials and chemicals.

The global seaweed industry has seen major growth, with research supporting the development of value chains for food, feed, and industrial products. It feeds the fastest growing aquaculture sector, employing millions of people worldwide. Collaboration between scientists, policymakers, and industry stakeholders has been instrumental in promoting sustainable practices. Research data has successfully influenced policy decisions, emphasizing the need for marine spatial planning to balance seaweed cultivation with environmental conservation. Additionally, international collaborations have facilitated knowledge sharing and capacity building in emerging seaweed-producing regions.

2) Main Contributions of the French Communities through ANR (co)funding (Action plan and France 2030)

The projects funded by the French National Research Agency (ANR) have significantly contributed to advancing knowledge on algae by exploring various aspects of their ecology, biotechnology, and ecosystem services.

2-1 Scientific progress; cutting edge science

The availability of genome sequence information from both brown (Cock et al, 2010, Ye et al, 2015, Denoeud et al 2024) and red macroalgae (Collén et al, 2013, Lipinska et al, 2023) has allowed some comparative analyses, but experimental investigation of the molecular basis of developmental processes in these algae is essential. The recent demonstration within [Bi-Cycle] that key developmental genes can be identified in the brown algal model Ectocarpus using a forward genetic approach represents a first step towards the emergence of experimental macroalgal developmental biology. Following Bi-Cycle, the project EpiCycle have completed an extensive characterisation of chromatin features in Ectocarpus. In addition to addressing life-cycle-related questions, these studies provided several new insights into chromatin function in the brown algae

Together with several other ANR-funded projects, IDEALG has contributed to the sequencing and analysis of reference genomes for dozens of brown and red algae and more than a hundred genomes of associated bacteria. This achievement was a major breakthrough for the biology of macroalgae. Based on these resources, genotyping tools have been developed for several species, either microsatellite markers or SNPs whose identification has been facilitated by new sequencing technologies. In parallel, phenotyping efforts have also been developed through culture, physiology and biochemistry tools to help determine the traits of interest for varietal selection. These tools were used in the framework of IDEALG, as well as in other projects on new species based on data acquired on the model species Ectocarpus. Over the course of 10 years, IDEALG has developed modules for processing genomic, genetic, biological and chemical information that have also contributed to developing biotechnological tools for projects completed with companies on a national and international scale. More than 450 recombinant proteins have been expressed by the SBR platforms, mainly enzymes for the degradation of algal biomass from specialized marine bacteria, but also more than ten algal proteins involved in the synthesis pathways of metabolites of interest such as phlorotannins, sterols, halogenated compounds or derivatives of oxidized fatty acids. Functional genetics tools for non-model bacteria or brown algae are also revolutionizing approaches to identify new functions or reveal new aspects of algae biology and metabolism. Made available to the scientific community within the national biology infrastructure European Marine Biological Resource Centre EMBRC-Fr, these results and these biological and genetic resources provide a better understanding of the physiology, reproduction, metabolism and interactions of algae with their environment.

Calcareous red algae represent an important functional group in the coral reef ecosystem and yet knowledge remains fragmented. The results obtained during BIOCARRA show the relevance of integrative taxonomy approach (morphology, ecology and genetics). 

2-2 Innovation for private enterprises, for science policy, for the citizen with a focus of coastal communities

Some major seaweed compounds such as sulphated polysaccharides and fibers have also found commercial applications in agriculture, animal farming, medical field and to provide substitute to oil-based products such as surfactant developed by the start-up Surfact’green in Rennes. Projects such as the Labcom ALGAHealth and Anti Foul provided solutions close to the market in their respective fields.

Biomimetism and green chemistry approaches are very promising research strategies for the discovery of new antifouling compounds. ANTI-FOUL focused on the red alga Sphaerococcus coronopifolius, which is known as a producer of bioactive secondary metabolites. Fifteen compounds, including bromosphaerol, were tested against key marine biofoulers. This investigation also revealed that two compounds, sphaerococcinol A and 14R-hydroxy-13,14-dihydro-sphaerococcinol A, were the most potent compounds without toxicity towards oyster larvae (Quemener et al. 2021).

The evaluation of the potential for producing bioethanol from cellulosic green seaweed and the proof of technical concept and sustainability were investigated during GreenAlgOhol. Life Cycle Analysis of the whole system helped identify the main aspects requiring optimization, in particular with regard to algae cultivation. The project also led to the identification and production of new types of polysaccharides and to the discovery of novel enzymes involved in the degradation of algal polysaccharides.

The portfolio of seaweed-specific enzymes coming from the ANR-funded projects Breakingalg, that forms the basis for the creation of the start-up “Aber Actives” based in the small coastal town of Roscoff, has considerably enriched knowledge, in particular by making it possible to use these enzymes to generate bioactives for markets in cosmetics, agriculture and nutraceuticals.

The valorization of FUCOTHROMBO through the production of medical grade LMWF fucoidan by Algues et Mer providing economic revenues and high skills jobs on the remote Ushant Island (Finisitère, Brittany), allowed this SME to gain international leadership in its preparation and marketing, and to develop new applications in collaboration with companies specialized in nuclear imaging, Nuclear Magnetic Resonance, ultrasound and with a pharmaceutical company for a therapeutic application. 

Monitoring & management of invasive macroalgae and valorization strategies: monitoring and managing invasive macroalgae, such as Sargassum and Ulva,  has become increasingly important to mitigate their environmental impact. Fine remote sensing technologies and advanced modeling tools are still needed to accurately track algal blooms and predict large-scale strandings. Early detection will be essential for more effective responses and better management of affected ecosystems. It will be important as well to keep on working on valorization strategies help to reduce waste while also creating sustainable resources. By focusing on these areas, future research could provide the scientific, technological, and policy-based solutions needed to address the challenges posed by invasive macroalgae, turning a potential environmental threat into an opportunity for sustainable innovation.

Yet, wild seaweed communities are predicted to lose up to 71% of their current distribution by 2100, either through overharvesting or climate-driven impacts, such as pollution, invasive species or pest and disease outbreaks. Therefore, interdisciplinary projects such as ECOKELP, and in its continuation IDEALG were anticipating these consequences and provided a forum to disseminate research results and transfer knowledge toward ecosystem management, Marine-protected areas and marine spatial planning. 

A major breakthrough during the last decade for seaweed-processing companies was the access to novel biotechnological developments. A major methodological breakthrough within projects ECOKELP and IDEALG was the need to co-construct research and development projects with their main stakeholders. This led to the many new collaborative projects funded by EMF (EMFAF) grants to develop seaweed cultivation associated with shellfish farming and piloted by professional organisations from several coastal regions across France.

3) Research perspectives coming out of the ANR (co)funded projects

3-1 For Scientific aspects

Despite remarkable progress, challenges remain in seaweed basic research. These include:

• Deciphering biological processes behind the production of active compounds
• Addressing knowledge gaps in the carbon dynamics of seaweed ecosystems and their contributions to global carbon budgets.
• Understanding the long-term ecological impacts of large-scale seaweed farming.
• Enhancing genetic resources for selective breeding and conservation.

Apart from commercial or academic concerns, the impacts of a warming climate on algal health and the role of these taxa as biomarkers of environmental change are also of paramount importance. Future research should prioritize multidisciplinary approaches, integrating biological, ecological, biotechnological, and socioeconomic perspectives to unlock the full potential of seaweeds in addressing global challenges such as climate change, food security, and sustainability for a circular bioeconomy.

The recent development of CRISPR-Cas9 methodology for brown (Badis et al., 2021) and green macroalgae (Ichihara et al, 2022) together with the other tools and resources currently available for the model brown alga Ectocarpus, and the genus Ulva provide the means to deploy the functional genomics approaches necessary to address numerous biological questions.

Research on macroalgae is rapidly expanding due to their potential contributions to the blue bioeconomy, ecological transition and biotechnological innovations. 

3-2 For Innovation as increase the TRL 

One major requirement for the scale-up of the seaweed sector is the development of replicable and cost-effective cultivation technologies to meet a growing demand.

Several key research areas are emerging :

• Seaweed breeding and optimization of sustainable aquaculture practises: Developing improved seaweed strains with higher growth rates, increased disease resistance, and enhanced adaptability to environmental changes (such as temperature fluctuations and ocean acidification) will provide significant competitive advantage to the seaweed market, ensuring higher yields, improved resilience and more sustainable production ; Moreover, improved biobanks and culture techniques will enable large-scale propagation of high-performing seaweed strains, ensuring genetic safety and disease-free seedlings. This method supports the sustainable supply of juvenile seaweed, reducing reliance on wild populations and ensuring year-round production. Breeding programs which are tailoring seaweed strains will significantly contribute to meet industry-specific needs such as high-protein strains for alternative proteins in food applications, enhanced polysaccharide content for bioplastics and pharmaceutical would provide a significant progress.
• Innovative cultivation techniques in macroalgae farming:  Advancements in artificial intelligence (AI) has already started to revolutionize macroalgae farming, making production more efficient, scalable, and sustainable. The further development of such technologies will contribute to optimize growth conditions (AI-powered sensors and imaging systems continuously monitor seaweed growth, detecting variations in biomass accumulation and identifying optimal harvest times) and to enhance disease management and stress detection (machine learning models analyze environmental data to predict and prevent disease outbreaks, reducing the need for chemical interventions).
• Biorefineries and zero waste approach: seaweed biorefineries involve extracting multiple high-value products from the biomass through various processes, such as fermentation, enzymatic treatment, and pyrolysis, while ensuring that little to no waste is produced in the process. There are three main challenges to overcome to ensure that the success of biorefineries: technological development of the processes for extracting, converting, and valorizing seaweed  (innovation in methods such as enzyme-assisted extraction, fermentation, and conversion technologies is crucial to improving efficiency and reducing costs), scalability (ensuring that the processes are compatible with the industrial scale), and  green chemistry) and green chemistry (green chemistry principles must be integrated into the entire process, from raw material to final product, to ensure that the biorefinery operates in an environmentally responsible manner). By addressing these interconnected challenges, seaweed biorefineries can become a cornerstone of the green economy, producing high-value, sustainable products while minimizing their environmental impact. As research, technology, and sustainable practices continue to evolve, the vision of a global, circular seaweed-based bioeconomy becomes increasingly achievable.

3-3 Structuration of the communities: at the national level, at the European level and/or at the international dimension

In France, the research on seaweed is structured through a combination of academic institutions, governmental agencies, and private-sector collaborations. Key actors include the French National Centre for Scientific Research (CNRS), the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), the National Natural History Museum (MNHN), various universities with marine biology and biotechnological research programs and some technical centers developing seaweed valorisation or aquaculture. National funding is provided through agencies such the Agence Nationale de la Recherche (ANR), supporting projects on seaweed applications in food, biofuels, and pharmaceuticals. Some Regional Councils provide also a long-lasting support to the seaweed research. A national roadmap is now launched to implement the EU Algae initiative in France and will likely enhance the efforts of the Funding Agencies on targeted research goals. Additionally, industry clusters such as Pôle Mer Bretagne Atlantique foster collaboration between researchers and companies in algal biotechnology. 
At the European level, research on seaweed is structured through major collaborative frameworks, particularly under the Horizon Europe program, which funds projects on marine biodiversity, blue economy, and sustainable aquaculture. The European Algae Biomass Association (EABA) acted as a key platform connecting academia, industry, and policymakers and it is now helped by other organisations to build the EU4 Algae platform that is implementing the EU Algae Initiative. Initiatives like GENIALG (Genetic diversity exploitation for innovative macro-algae biorefinery) and Seaweed for Europe promote large-scale industrial applications and sustainable harvesting techniques. Furthermore, the Joint Programming Initiative on Healthy and Productive Seas and Oceans (JPI Oceans) supports transnational research on seaweed’s role in carbon sequestration, climate adaptation, and ecosystem services, and, the Sustainable Blue Economy Partnership represents an unprecedent effort of 74 Partner institutions from 30 countries and the European Commission to pool research and innovation investments and align national programmes at pan-European scale. 

Globally, seaweed research is expanding, with contributions from United Nations organizations like the Food and Agriculture Organization (FAO), which provides guidelines on sustainable seaweed farming. The Global Seaweed SuperSTAR project, led by the United Nations University and World Bank, supports sustainable seaweed production in developing countries. Countries such as Japan, China, and South Korea lead in large-scale cultivation and industrial applications, often collaborating with European and American research institutions. Global networks such as the International Seaweed Association (ISA) and the Global Seaweed Coalition co-funded by CNRS in France, UN Global Compact and the Lloyd’s Register Foundation facilitate knowledge exchange on seaweed genetics, cultivation methods, and novel biotechnological applications, ensuring a coordinated international effort in seaweed research. These initiatives would lead to the launch of a UN Task Force that will be created by the endorsement of the Republic of South Korea and Madagascar and other states that will engage in the sustainable development of a global seaweed sector.

The structuration of seaweed research operates at multiple levels, ensuring that scientific advances align with national priorities, European policy frameworks, and international sustainability goals. Increased collaboration between these levels is crucial for developing innovative and sustainable uses of seaweed in food security, climate mitigation, and the bioeconomy. An important instrument to reach such ambition will be to create International Research Centres following the examples of the main agricultural crops with regional hubs. Such an initiative was announced in 2024 by the Indonesian Government to operate an International Tropical Seaweed Resilience Institute (https://hatchinnovationservices.com/tropical-resilience-center-report). EMBRC could support the hub for such a centre for European seaweeds.