Tamil Nadu Red Seaweed Trial Shows 7.6× Biomass Growth

A raft-based cultivation trial by ICAR–Central Institute of Brackishwater Aquaculture demonstrated rapid growth of red seaweed Gracilaria salicornia in Muttukadu lagoon, south of Chennai. The peer-reviewed study was published in Blue Biotechnology on 1 July 2025 and newly reported in science media on 1 October 2026. The experiment used 12 bamboo rafts of 3 sq m each, giving a total trial area of 36 sq m. Each raft carried 12 tube nets stocked with 1. 2 kg of seaweed.

Biomass reached 5. 07 kg per tube net by day 15, 7. 67 kg by day 30 and 9. 09 kg by day 45. Compared with the initial weight, the day-45 biomass was about 7.

6 times higher. Salinity during the trial ranged from around 20 to 31 PSU, showing tolerance of fluctuating brackishwater conditions. Gracilaria is commercially important because it is a source of agar used in food, microbiology, pharmaceuticals, cosmetics and biotechnology. The study also modelled a 50-raft system, estimating ₹90,000 initial cost, 710. 65 kg annual dried seaweed output, seven annual cycles, first-year net return of about ₹24,362 and second-year onward annual net return of about ₹1.

14 lakh under stated assumptions. The results do not prove suitability of every lagoon, but they establish a measurable technical baseline for coastal livelihood pilots. For coastal planners, the finding is useful because it shifts seaweed discussion beyond open-sea farming alone. Brackishwater sites can offer sheltered conditions, but they also require site-specific salinity, water-quality, navigation, biodiversity and storm-risk assessment before farmer groups invest at commercial scale. Commercial pilots will also need ecological carrying-capacity checks before cultivation is expanded to additional lagoons or estuaries.

Original source references: Blue Biotechnology/Springer Nature, 1 July 2025; Bioengineer, 1 October 2026; PIB Fisheries, 10 February 2026.

Rural Development Today | 2 October 2026 | Development Connects | Kallol Saha