Controlled laboratory culture of Argentine Gelidium species: comparative assessment of mesh bag and free-floating systems for enhanced productivity

Abstract

Gelidium is the principal source of high-quality bacteriological agar, yet global production relies almost entirely on wild harvesting due to the lack of economically viable cultivation methods. In Argentina, two native species, Gelidium carolinianum and G. crinale remain unexploited. The aim of this study was to establish the first experimental cultivation protocol for Argentine Gelidium species by comparing mesh bag and free-floating systems, optimizing seeding density, and assessing epiphytic load. Thalli of both species were cultured under controlled laboratory conditions (18°C, 60 µmol photons m-2 s-1, 12:12 h photoperiod) for 60 days. An experiment evaluated cultivation system (mesh bags vs. free-floating) thallus integrity (whole vs. fragmented), and seeding density (14 vs. 50 mg per 100 mL). Fresh weight, daily growth rate (DGR), and epiphytic algae incidence were quantified. Mesh bag cultivation significantly outperformed free-floating systems, yielding DGR values of 3.92% vs. 2.11% day-1 for G. carolinianum and 3.28% vs. 1.06% day-1 for G. crinale. Fragmented thalli of G. crinale showed 46% higher DGR than whole thalli, whereas G. carolinianum exhibited equivalent performance regardless of integrity. Lower seeding density produced higher growth rates than high density. The mesh bag system reduced epiphytic diversity on thalli from 13 to 9 taxa, redirecting colonization toward the bag substrate. Mesh bag cultivation with optimized seeding density represents a scalable, effective method for onshore Gelidium biomass production. This study establishes the technical foundation for developing a sustainable culture technique for Gelidium species in Argentina.