Seaweed, also known as macroalgae, is a diverse group of marine plants that play a crucial role in marine ecosystems and offer numerous benefits to human health, the environment and various industries. It is a fascinating organism that thrives in aquatic environments and holds immense scientific and ecological significance. With a rich history spanning centuries, seaweed has played a pivotal role in numerous cultures and industries across the globe. Its unique morphology, varied species and adaptation to different environments contribute to its remarkable diversity and versatility.

Seaweed encompasses a vast array of multicellular marine algae that range from microscopic organisms to giant kelps. These plants lack true roots, stems and leaves but possess specialised structures such as holdfasts and fronds, that aid in anchoring and photosynthesis. Seaweed evolved from ancestral algae, with three main groups dominating today's oceans: brown algae (Phaeophyta), red algae (Rhodophyta) and green algae (Chlorophyta). Seaweed distribution is influenced by various factors, including water temperature, salinity, nutrient availability and light intensity. Different species exhibit varying preferences for these conditions, leading to their distribution across diverse habitats, from tropical reefs to temperate and polar regions. Some species thrive in intertidal zones, while others grow at greater depths, adapting to unique ecological niches.

Furthermore, seaweed contains a wide array of phytochemicals which are bioactive compounds that contribute to its health benefits. These phytochemicals offer various physiological effects and have sparked significant interest in scientific research. The following are some of the key phytochemicals found in seaweed and their associated health benefits:

a)     Polysaccharides: Seaweed is rich in different types of polysaccharides, including alginate, carrageenan and agar. These polysaccharides possess unique properties that make them beneficial for human health. Alginate, for example, has been shown to have prebiotic effects by promoting the growth of beneficial gut bacteria, thereby enhancing digestive health. Carrageenan exhibits antiviral and antitumor properties and agar is commonly used as a vegetarian gelatine substitute.

b)     Phlorotannins: Found predominantly in brown algae, phlorotannins are a class of polyphenolic compounds with potent antioxidant properties. These compounds scavenge free radicals, reducing oxidative stress and protecting cells from damage. Phlorotannins also exhibit anti-inflammatory effects, making them potentially beneficial in managing chronic inflammatory conditions such as arthritis.

c)     Fucoidans: Fucoidans are sulphated polysaccharides present in brown algae. They have been investigated for their numerous health benefits, including anticoagulant, antiviral and immunomodulatory activities. Fucoidans have also shown potential in inhibiting tumour growth and metastasis, making them a subject of interest in cancer research.

d)     Fucoxanthin: Fucoxanthin is a carotenoid pigment responsible for the brown colour in seaweed. It exhibits antioxidant properties and has gained attention for its potential role in weight management. Studies have suggested that fucoxanthin may help promote fat metabolism, reduce fat accumulation and regulate blood sugar levels, making it a promising natural compound for combating obesity and metabolic disorders.

e)     Omega-3 fatty acids: Certain species of seaweed, particularly those belonging to the red algae group, contain omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are essential for brain health, cardiovascular function and reducing inflammation in the body. Seaweed serves as a vegetarian and vegan source of omega-3 fatty acids, making it particularly valuable for individuals following plant-based diets.

f)      Iodine: Seaweed is one of the richest natural sources of iodine. Iodine is an essential mineral required for the synthesis of thyroid hormones, which regulate metabolism, growth and development. Adequate iodine intake is crucial for maintaining thyroid function and preventing iodine deficiency disorders, such as goiter. However, it's important to note that excessive iodine consumption from seaweed should be avoided, as it may lead to thyroid dysfunction in susceptible individuals.

g)     Antioxidants: Seaweed is replete with antioxidants, including vitamins (for example vitamins A, C, E) and various phytochemicals, which combat oxidative stress and help protect against chronic diseases such as cardiovascular disease, cancer and neurodegenerative disorders. Antioxidants in seaweed scavenge free radicals and inhibit oxidative damage, contributing to overall cellular health and well-being.

Unsurprisingly, seaweed also offers a multitude of industrial applications across various sectors due to its unique composition and properties. Seaweed has a long history of culinary use in many cultures and continues to be a popular ingredient in modern cuisine. It is used in the production of sushi, nori sheets, seaweed salads and as a flavour enhancer in broths and seasonings. Seaweed extracts are also employed as natural thickeners, stabilizers and emulsifiers in the food industry, replacing synthetic additives. Additionally, seaweed-derived compounds are explored for their potential as natural food preservatives.

Seaweed is also widely utilised in the cosmetics and personal care industry. Its high mineral content, vitamins, antioxidants and moisturising properties make it a valuable ingredient in skincare products, such as moisturizers, facial masks and anti-aging creams. Seaweed extracts can help hydrate the skin, improve elasticity and protect against environmental stressors. Additionally, seaweed-based extracts are used in hair care products to strengthen and condition the hair.

Similarly, the bioactive compounds found in seaweed have attracted significant attention from the pharmaceutical industry. Seaweed extracts and isolated compounds are being investigated for their potential therapeutic properties. For instance, seaweed-derived polysaccharides show promise as wound-healing agents, drug delivery systems and anti-inflammatory agents. Moreover, seaweed-based dietary supplements and nutraceuticals are gaining popularity due to their rich nutritional profile and potential health benefits.

Furthermore, seaweed extracts, such as seaweed fertilizers and bio-stimulants, are widely employed in agriculture and horticulture. These extracts enhance plant growth, improve crop yield and increase resistance to biotic and abiotic stressors. Seaweed extracts provide plants with essential nutrients, growth hormones and beneficial microorganisms, promoting healthier root systems and overall plant health. They are particularly advantageous in organic farming practices, as they are natural and sustainable alternatives to synthetic fertilizers.

Moreover, seaweed holds great potential as a source of renewable energy. It can be used as a feedstock for the production of biofuels, such as bioethanol and biodiesel. Seaweed biomass is rich in carbohydrates, which can be converted into fermentable sugars for biofuel production. Additionally, seaweed can be used in anaerobic digestion to produce biogas, a renewable energy source. Seaweed farms also have the advantage of absorbing carbon dioxide during their growth, contributing to climate change mitigation. Thus, seaweed cultivation and utilisation offer significant environmental advantages. Seaweeds act as carbon sinks, absorbing atmospheric carbon dioxide and reducing ocean acidification. They also serve as habitat and nurseries for various marine organisms, supporting biodiversity. Furthermore, seaweed farming can mitigate eutrophication by nutrient uptake and it requires no freshwater, arable land or fertilizers, making it an eco-friendly alternative to conventional agriculture.

Although seaweed is generally considered safe for human consumption, it's important to consider certain factors when incorporating seaweed into the diet or using seaweed-derived products. Seaweed can accumulate heavy metals, such as arsenic, cadmium, lead and mercury, from the surrounding water. The concentration of heavy metals in seaweed can vary depending on the location of cultivation or collection. It is essential to source seaweed from clean, uncontaminated waters and adhere to regulatory guidelines on acceptable levels of heavy metals in food and supplements.

In summary, the future of seaweed looks promising. With growing concerns over food security, climate change and environmental degradation, seaweed offers sustainable solutions. Research and development efforts are focused on enhancing cultivation techniques, exploring novel species and optimising extraction methods. The integration of seaweed farming with aquaculture and offshore renewable energy projects further strengthens its potential as a multifaceted sustainable resource.

Seaweed's historical significance, intriguing morphology and versatile applications make it a valuable organism for scientific study and sustainable development. Its health benefits, phytochemical composition and environmental advantages underscore its potential to revolutionise various industries and contribute to a more sustainable future. Continued research and innovation in seaweed cultivation, processing and utilisation will unlock new frontiers, enabling us to harness the full potential of this underwater treasure.

Renald Blundell is a biochemist and biotechnologist with a special interest in Natural and Alternative Medicine. He is a professor at the Faculty of Medicine and Surgery, University of Malta

Emma Camilleri is currently a medical student at the University of Malta