Optimizing Planting Density and Culture Systems in Kappaphycus alvarezii: A Systematic Review of Growth, Carbon Dynamics, and Carrageenan Quality

Abstract

Kappaphycus alvarezii is a globally important carrageenophyte underpinning food, pharmaceutical, and biomaterials industries while supporting coastal livelihoods in tropical regions. Despite its economic significance, production remains highly variable, with inconsistent biomass yields and carrageenan quality driven by environmental variability and heterogeneous farming practices. This systematic literature review synthesizes evidence published between 2000 and 2026 on how planting density and culture system configuration including tie-tie/longline systems, tubular nets, vertical columns, and related designs shape growth performance, carbon dynamics, and carrageenan quantity and functional quality in K. alvarezii cultivation. Drawing on PRISMA-guided screening, the review integrates findings across four themes: (i) density–growth relationships, (ii) farm configuration as micro-environmental engineering, (iii) carbon dynamics and physiological responses, and (iv) carrageenan yield and quality outcomes. The synthesis reveals a consistent intermediate-density advantage for growth efficiency and physiological stability, strong context dependence mediated by site-specific environmental conditions, and recurring trade-offs between biomass maximization and carrageenan quality. Carbon dynamics emerge as a critical mechanistic link connecting farm geometry to biochemical outcomes. The review highlights persistent challenges related to non-standardized density definitions, heterogeneous outcome metrics, and limited multi-site experimentation. By framing density and configuration as integrated farm-engineering levers, this review advances a multi-objective optimization perspective and proposes evidence-based operational windows and reporting priorities to support resilient, quality-oriented, and scalable K. alvarezii aquaculture.