High spatial and temporal variation in biomass composition of the novel aquaculture target Ecklonia radiata

Abstract

AbstractThe biomass composition of kelp varies within species both spatially and temporally. However, this variation in biomass quality has not yet been investigated for the native kelpEcklonia radiatawithin New Zealand, where the kelp is a target for the emerging seaweed aquaculture industry. In this study we quantified spatial and temporal variation in the composition ofE. radiatabiomass, collected from 12 sites around the North Island of New Zealand and from 12 months across a full year at a single site (n = 138). High spatial variation was detected for most components, including alginate (range: 16.6 – 22.7% DW,n = 12), fucoidan (range: 1.2 – 1.6% DW,n = 12), phlorotannins (range: 4.8 – 9.3% DW,n = 72), and glucose (range: 9.3 – 22.6% DW,n = 12). The biomass composition ofE. radiatavaried significantly among sites but with no clear patterns among regions, indicating that geographic differences were mostly local rather than regional, possibly due to site-specific environmental conditions. Significant temporal variation (measured by positive autocorrelation between months) was detected in the content of lipids, proteins, glucose, guluronic acid, nitrogen, phosphorous, iodine, arsenic, and mercury, and for the mannuronic to guluronic acid (M:G) ratio. Overall,E. radiatahad comparable biomass composition to that of commercially grown northern hemisphere species but with substantially higher phlorotannin content. These results demonstrate thatE. radiatacould be a viable southern hemisphere alternative for a broad range of commercial applications.