Novel Methods to Improve the Biomass of Seaweeds

Seaweeds such as phycocolloids (agar, carrageenan and alginate) have been utilized for food for more than a century. Globally, about 221 species currently having commercial utility, only ten species are being commercially cultivated and have a market value of US$11.7 billion. Among the ten species, Eucheuma sp. (35%), Laminaria japonica (27%), Gracilaria sp. (13%), Undaria pinnadifida (8%), Kappaphycus alvarezii (6%) and Porphyra sp. (4%) have a major share in global seaweed biomass production (FAO, 2018). Seaweed's phycocolloids production in 2015 was 93,035 tons wt and had a market value of US$1058 million. Although there are 844 species reported in India, only a few seaweed species such as Gelidiella acerosa, Gracilaria edulis, Sargassum sp. and Turbinaria sp. are commercially explored for agar and alginate production. Chaotic harvesting in natural seaweed beds leads to over-exploitation, resulting in depletion of natural resources. The Central Salt and Marine Chemicals Research Institute (CSIR-CSMCRI) has developed technology with scientific efforts for cultivating certain commercially valuable seaweeds in Indian waters. Cultivation techniques (vertical/horizontal mode of cultivation) determined based on habitat, depth of cultivation site, season, planting method (tie-tie/direct insertion into ropes). Initially, rope culture was attempted for G. edulis cultivation and later, Single Rope Floating Technique (SRFT) was developed. The polythene bag, net bag and monoline/longline method were developed for Kappaphycus alvarezii cultivation. For effective biomass production in the intertidal region, the raft method was developed for Kappaphycus alvarezii, Gracilaria debilis, Gracilaria dura and G. edulis. For rough and open sea culture, tube net was developed for Kappaphycus alvarezii and Gracilaria dura. The net bag method is well suited for storing germlings or seed stocks during the lean period. All the technology developed for algal biomass production satisfies the worldwide customary Daily Growth Rate (DGR) range of 3.5% day−1.