Seaweeds: Significance, Potential & Challenges in Cultivation

Context (PIB): In a significant step towards enhancing marine-based livelihoods and sustainable resource use, India has identified 384 potential sites across 24,707 hectares for seaweed cultivation.

About Seaweed

Marine Algae: Seaweeds are macroscopic marine algae found along rocky and sandy coastlines.
Colour Range: They appear in red, brown, green, or black based on pigment type.
Size Variation: Species range from tiny algae mats to giant kelp over 60 metres long.
Rootless Structure: Seaweeds lack true roots, stems, or leaves but carry out photosynthesis efficiently.

Salinity Range: Optimal growth occurs in waters with salinity above 30 ppt.
Temperature: Preferred temperature lies between 26°C and 30°C.
Depth Requirement: A minimum water depth of 1 metre during low tide is essential.
Substrate Type: Seaweeds grow best on rocky bottoms in clear waters.
- Transparent water ensures adequate sunlight penetration for photosynthesis.
Water Movement: Mild water currents are ideal for maintaining nutrient flow and oxygen supply.
Fast Growth: Certain seaweed species can double biomass in 10–15 days under ideal conditions.

Photosynthetic Output: Seaweeds generate up to 50% of the Earth’s oxygen.
Marine Food Chain: They support herbivores like molluscs, fish, and turtles.
Nutrient Cycling: Seaweeds absorb nitrogen and phosphorus, reducing eutrophication.

Edible Use: Seaweeds are consumed in sushi, salads, snacks, and seaweed-based condiments.
- They are rich in iodine, fibre, vitamins, and antioxidant compounds.
Industrial Application: Seaweed compounds act as binding agents in toothpaste, jelly, and as emollients in organic cosmetics.
Fertiliser Input: Liquid extracts from seaweeds act as bio-stimulants in organic agriculture.
Pharmaceutical Use: Compounds offer anti-inflammatory, anti-cancer, & heart-protective properties.
Bioenergy Source: Seaweeds are processed for bioethanol and biogas as renewable fuel alternatives.

Livelihoods: Seaweed farming creates low-investment income opportunities for marine communities.
Climate Mitigation: Seaweed farms absorb dissolved CO₂ and help reduce ocean acidification.
Import Substitution: India currently imports carrageenan despite having native red seaweed varieties.
- Carrageenan: It is a phycocolloid (gel-forming compound) extracted from red seaweeds.
Marine Habitat: Seaweed beds offer shelter and breeding zones for fish and invertebrates.
Value Addition: Seaweed supports nutraceutical, cosmeceutical, and bioplastic-based manufacturing.
Agriculture Linkage: Bio-stimulant use improves soil health and crop productivity in organic farming.

Tamil Nadu contributes nearly 80% of India’s seaweed output, led by the Gulf of Mannar.

Seed Scarcity: Limited quality planting material hinders the growth of seaweed farming.
Labour Shortage: Seasonal agricultural work reduces worker availability for seaweed activities.
Disease Threats: Epiphytes and pathogens cause major biomass losses and yield instability.
Climate Sensitivity: Seaweed species are vulnerable to rising sea temperatures and shifts in salinity.
Regulatory Delays: Lease approvals, zoning clearances, and germplasm norms cause project delays.
Red-Tide Events: Harmful algal blooms pose a seasonal risk to large-scale seaweed cultivation.

PMMSY Funding: ₹195 crore was sanctioned for seaweed sector development during 2020–25.
Seaweed Park: A multipurpose seaweed park was approved in Tamil Nadu with ₹127 crore support.
Lakshadweep Cluster: The Union Territory was designated as a national seaweed farming cluster.
Centre of Excellence: ICAR–CMFRI Mandapam was declared India’s seaweed R&D hub.

Seaweed cultivation has been designated a priority activity under Pradhan Mantri Matsya Sampada Yojana (PMMSY) to expand marine-based income diversification.