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

The 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 kelp Ecklonia radiata within 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 of E. radiata biomass, 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 of E. radiata varied 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. radiata had comparable biomass composition to that of commercially grown northern hemisphere species but with substantially higher phlorotannin content. These results demonstrate that E. radiata could be a viable southern hemisphere alternative for a broad range of commercial applications.

Automated summary

The biomass composition of Ecklonia radiata, a native kelp species in New Zealand, shows significant spatial and temporal variation. This study examined the composition of E. radiata biomass collected from different sites across the North Island of New Zealand and throughout a year at a single site. The results revealed high spatial variation in the biomass components and significant temporal variation in several key parameters. Overall, E. radiata could serve as a viable alternative for various commercial applications, with comparable biomass composition to northern hemisphere species but with higher phlorotannin content.