Tube net cultivation of Kappaphycus alvarezii in floating high density polyethylene raft - a feasibility study in exposed coastal waters in Northeastern Indian Coast

Megarajan, Sekhar and Ranjan, Ritesh and Johnson, B and Xavier, Biji and Ghosh, Shubhadeep and Durga Suresh, R and Raju, S S and Gopalakrishnan, A (2024) Tube net cultivation of Kappaphycus alvarezii in floating high density polyethylene raft - a feasibility study in exposed coastal waters in Northeastern Indian Coast. Journal of Applied Phycology, 36. pp. 2739-2755. ISSN 1573-5176

Text Journal of Applied Phycology_2024_Sekar Megarajan.pdf Restricted to Registered users only Download (1MB) | Request a copy

Abstract

Commercial-scale seaweed production in exposed coastal waters has failed due to the absence of appropriate culture methods. In the present study a novel tube-net based seaweed cultivation in floating high-density polyethylene (HDPE) raft structure was developed for exposed and deeper coastal waters. The design prototype was evaluated by culturing Kappaphycus alvarezii, in the northeastern Bay of Bengal Sea, off the Visakhapatnam coast, India, for its structural stability, seaweed culture potential, and economic feasibility. A square-shaped HDPE raft of 3 × 3 m, was tied with ten tube nets of each 3.0 m length and 0.32 m dia, made of HDPE net. A cluster of 25 rafts deployed as a single unit and the entire system was stabilized by a multipoint mooring system. The raft structure with seaweed, along with the anchoring system endured the high waves (1.34 ± 0.08 m) and wind speed (11.5 ± 0.62 km h-1) and had supported for seaweed growth. Four different initial seeding biomasses (3, 5, 7.5, and 10 kg tube-net-1) were assessed for growth in a total of six cycles with a culture duration of 45 days cycle-1. The growth parameters were observed to be significantly higher (p<0.05) at initial seed biomass of 5 kg tube-net-1, with a maximum daily average growth rate (3.52% day-1) and net biomass (191.11 kg raft-1 crop-1). Pearson’s correlation coefficient (r) at 0.05 level showed a significant negative correlation of growth parameters to temperature, and salinity and a positive correlation with phosphate content in the seawater. Annual economic returns of US$ 2061.83 were calculated for a cluster unit with a profit margin of 31.35%. However, this method faces many challenges, including high initial investment, labour involvement, and inclement weather that hampers estimated biomass projection. In spite, the present method of seaweed farming was found suitable for exposed seas up to 10.5 m water depth, and can be adopted in seas with similar dynamics to promote seaweed farming.

Actions (login required)

View Item