[In-depth] Seaweeds – From health benefits to climate change mitigation
After Prime Minister Narendra Modi emphasised developing the blue economy in coastal states and asked stakeholders to re-focus on seaweed farming and research, the latter has been carried out in full swing during the pandemic years. Seaweeds (macroalgae) have been put to various uses, particularly, in the food, agro and pharma sectors.
What is Seaweed?
Seaweeds are also known as Macroalgae. They constitute several species of marine plants and algae. Seaweeds may also include Red, Green and Brown algae. Seaweeds can grow in ocean, rivers, lakes and other water bodies. There are many types of seaweeds such as nori and laver seaweed. Seaweeds are attracting interests all around the world for its potential in commercial exploitation and the sustainability needs.
What are the characteristics of Seaweeds?
- Seaweeds are macroscopic and multicellular organisms.
- Some species of seaweeds are microscopic such as phytoplankton.
- Seaweed can be as small as the one-celled phytoplankton or as large as giant kelp.
- Even though seaweeds are not categorised as plants, it also requires light, water and nutrition for the growth and sustenance.
How does seaweed grow?
Water and Nutrients
- Unlike plants and seagrass, seaweeds don’t require roots or a mechanism for transporting water and minerals. It is because all parts of the seaweed touch the water and they can absorb what they need directly from the water through surface tissues. So it doesn’t need an internal conducting system like land-based plants do.
- A unique feature of seaweeds is holdfasts that serve as an anchorage and makes seaweed grow instead of float away by means of attaching to hard surfaces such as seafloor, hard-shelled molluscs, boats or ships.
Light and Photosynthesis
- Seaweed is photosynthetic and hence it harnesses sunlight for production of energy through chlorophyll pigment.
- As the light under the water surface is very low, seaweed utilises other pigments for harnessing sunlight not properly absorbed by chlorophyll.
- Some species of seaweed floats or having air-filled pockets that makes them come closer to the water surface for increased photosynthesis.
Where does seaweed being cultivated?
- Seaweed grows along rocky shorelines throughout the world, but it is mostly cultivated and eaten in Asian countries like Japan, Korea and China.
- Asia is the world leader in seaweed cultivation and more than 80% of the seaweed production is from China, Japan and Korea.
- Seaweeds are also being consumed as food by indigenous people in New Zealand, Northwest America, and parts of the British Isles.
Benefits of Seaweed
- Seaweeds are primary producers in the marine ecosystem and essential for numerous marine organisms for food and habitat needs. For instance, phytoplankton (a microscopic seaweed) live suspended in the water column and serves as the base for almost all marine food chains.
- Seaweeds can also improve the conditions of coastal waters for the benefit of other living organisms and the environment.
- Seaweed cultivation holds enormous potential in improving the livelihood as well as increasing the sustainability of fish farming through integrated practices.
- It also provides development and alternative livelihood opportunities for the underprivileged coastal communities across the world, where overfishing is a common practice.
- Seaweed is a source of multiple components such as polysaccharides, proteins, phenols etc. which have enormous commercial value.
- It can be used as effective emulsifiers or binding agents in goods such as toothpaste and fruit jelly.
- They can also be used as softeners or emollients in organic cosmetics and skin-care products.
- Seaweed is highly nutritious full of vitamins, minerals and fibre, but also tastier.
- Brown seaweed benefits include proper Thyroid functioning as it contains iodine and tyrosine.
- It holds different varieties of protective Antioxidants that makes unstable substances called free radicals in the body less reactive.
- Seaweed helps in losing weight by delaying hunger and reducing weight.
- It also reduces the risk of heart disease
- Seaweed may help lower the risk of Type 2 diabetes by improving control in blood sugar level.
- Dried seaweed or Kelp is a common addition to Japanese dishes such as sushi. Benefits of dried seaweed include healthy brain function and increased immunity.
- Seaweeds contain anti-inflammatory and anti-microbial agents. Ancient Romans used them to treat burns, wounds and rashes.
- Some seaweeds possess effective cancer-fighting agents that will prove to be effective in the treatment of tumours and leukaemia. Anecdotal evidence suggests that Ancient Egyptians may have used seaweeds for the treatment of breast cancer.
- During the pandemic, hand sanitizers were also made from this plant.
- Liquid seaweed fertilizer is organic as well as sustainable and can be harvested without damaging the environment.
- Seaweed fertilizers contain potassium, magnesium, zinc, iron and nitrogen – which are beneficial for crops. For instance, nitrogen is crucial in the production of nitrate, an important component required by plants during photosynthesis.
- Crops grown with seaweed fertilizers have larger root mass, stronger growth and higher survival rates. It also improves yield.
- Seaweed also serves as a good feed for the farm animals.
- Seaweeds can be converted to various types of fuels such as Biodiesel, Bioethanol and butanol.
- Like fossil fuels, Seaweeds also produce CO2 when burnt, but it is carbon neutral, which means, it only release CO2 which were recently removed from the atmosphere through photosynthesis during the growth of seaweeds.
Mitigation and adaptation of Climate Change
- Both wild and farmed seaweeds can contribute as carbon sinks by removing carbon directly from the water column and keeping it in their tissues. With this ability to store carbon for a longer term, seaweeds help fight climate change.
- Seaweed also helps lower the Green House Gases (GHGs) emissions from agriculture by increasing soil quality through replacement of synthetic fertilizer and also by lowering methane emissions from cattle when it is included in cattle feed.
- It also helps in climate change adaptation by breaking wave energy, defending shorelines and by increasing pH and providing oxygen to the waters, thus lowering the effects of the ocean acidification and de-oxygenation.
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What are the disadvantages of seaweeds?
- Seaweed can contain a dangerous amount of Iodine which can cause goitre, high thyroid-stimulating hormone level, and hypothyroidism.
- Seaweed also holds large amounts of toxic heavy metals such as lead, mercury, Arsenic and lead. It is because seaweed can absorb and store minerals in high amounts.
- Seaweed can help mitigate climate change by reducing methane emissions from the cow, but it also contributes to ozone layer depletion. When Cow eats seaweed, a chemical called bromoform is produced inside its body. Bromoform has the potential to deplete the ozone layer. Studies reveal that Bromoform may also increase the risk of cancer in some animals.
- Decomposition of dead seaweed consumes oxygen from the water column leading to the deprivation of oxygen for respiration for other organisms.
- It also has localised impacts such as decreased sunlight, shifts in seawater temperature and reducing nutrients in the water.
- Furthermore, seaweed has the potential to become an invasive alien species wherever they are introduced, as they can grow and spread rapidly and quickly consuming most of the nutrients for themselves.
What are the challenges in seaweed aquaculture?
- Besides the disadvantages of seaweed, seaweed aquaculture is also limited by several factors such as the availability and competition for suitable areas, need for engineering systems to cope with rough conditions offshore, less market demand for seaweed products etc.
- There are also challenges to overcome in the science and technology front. There is a need to develop strains with heat-tolerance, disease resistance, faster growth, and the development of more cost-efficient farm systems that can withstand storm conditions in offshore regions.
- Seaweed or algal biomass consumes a huge amount of water and it also has the tendency to reduce the nutrients such as nitrogen in any body of water.
- Traditionally the raft method is used where bamboo raft-like structures containing shelves, which are prone to breakage and drifting off in case of a rough sea and cyclone.
What is the Indian scenario?
- With China, Korea and Japan contribute more than 80% of seaweed cultivation, India also discovered the opportunity to become a player in the market.
- India, with a total coastline of 7,517 km across its states and islands, has around 844 species of seaweeds. There are 60 commercially important seaweed species available in India.
- In India, seaweeds grows abundantly along the Gujarat and Tamil Nadu coasts and around Andaman & Nicobar islands and Lakshadweep.
- Seaweed industry in India is primarily a cottage industry and is based on agar yielding red seaweeds such as Gelidiella acerosa and Gracilaria sp. which are harvested throughout the year and algin yielding brown algae like Sargassum and Turbinaria which are harvested seasonally from August to January on Souther coast.
- There are also a presence of rich seaweed beds around Chilka in Odisha, pulicat in Tamil Nadu, Mumbai, Goa, Karwar, Varkala and Vizhinjam.
- Seaweed is crucial in times when India pledged to improve emissions intensity of its GDP by 33-35% by 2030 below 2005 levels, under its INDC (Intended Nationally Determined Contributions).
- Seaweed will also help India improve livelihood especially for small farmers living near the coast.
- It will help solve the problem of farmer suicides when it is used as fertilizers which will improve crop yields.
- In India, Commercial seaweed cultivation got a fillip after PepsiCo began seaweed farming in Tamil Nadu in 2005. Central Salt and Marine Chemicals Research Institute (CSMCRI), Gujarat, also began noticing the commercial and social potential of seaweed farming and it identified and conducted extensive seaweed cultivation trials in coastal Tamil Nadu for PepsiCo. In 2012, the then Chief Minister of Gujarat, Narendra Modi, invited Gujarat Livelihood Promotion Company (GLPC) to join in to fight against high malnutrition levels in the state with the help of the seaweed farming.
- To counter the challenges associated with raft method aquaculture, scientists have devised an innovative HDP (high density polyethylene) Tubenet and grid-mooring method.
- Government marine scientists from top research institutes – namely the Central Marine Fisheries Research Institute (CMFRI) and Central Institute of Fisheries Technology (CIFT) under the aegis of Indian Council of Agricultural Research (ICAR) have come up with diversified and interesting natural, seaweed-based products and culture, which are primarily produced along the coasts of Tamil Nadu, Andhra Pradesh, Kerala and Gujarat.
What is the way forward?
To ensure the sustainability of seaweed cultivation and its acceptance as an environmentally sustainable activity, a coordinated international effort in research of seaweeds is immediately needed for studying the genetic resources and create effective genetic conservation policies. There is also a need to start investigating the long-term environmental impacts of seaweed cultivation since the post-disease management measures are far more costly and less efficient than the science-based preventive policies.