Gracilaria debilis cultivation, agar characterization and economics: bringing new species in the ambit of commercial farming in India

Abstract

Gracilaria debilis (Forsskål) Børgesen, an economically important red alga, was cultivated for 2 years by a floating bamboo raft method from November 2014 to October 2016 along the southeastern coast of India in order to evaluate possibilities for its year-round cultivation. This was achieved by analyzing biomass yield, growth rate, and agar properties from each harvest. Bench-scale agar characterization and economics were calculated for the first time for G. debilis. Higher biomass yields were recorded during first harvest (November–December) of both the first (11.02 ± 2.08 kg fr.wt m−2) and second (7.17 ± 3.95 kg fr.wt m−2) years. Similarly, higher growth rate was recorded during the first harvest of the first (3.59 ± 0.4% day−1) and second (4.17 ± 0.96% day−1) year, respectively. Biomass yield and DGR were at their minima during monsoon season (i.e., July–August). There was no clear trend pertaining to yield and gel strength of the extracted agar which were in the range of 14–32.6% and 300–866 g cm-2, respectively. This study confirmed that year-round cultivation of G. debilis is possible in Indian waters using the raft culture method with six harvest cycles per annum. The annual income for a single operator was estimated to be US$141, while break-event point per hectare could be achieved after 126 days.