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

Abstract

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.

Bacteroidia and Clostridia genomes collectively encode for a progressive cascade of marine polysaccharide degradation along the hindgut of the herbivorous fishKyphosus sydneyanus

“…Therefore, the gastrointestinal tract of K. sydneyanus is enriched with a diverse array of carbohydrates such as alginate, laminarin, mannitol, and fucose-containing sulfated polysaccharides (FCSP) present in brown algae species. In addition, the gut contains carrageenan, agarose and floridean starch from dietary red algae [5, 7–9]. These substrates likely constitute the bulk of fermentation substrates supplied to gut microbial communities and govern metabolism along the fish gut.…”

“…Next, we determined the carbohydrate active enzyme (CAZyme) repertoire encoded by these genomes, and the capacity to break-down polysaccharides, particularly those comprising the K. sydneyanus diet of brown (e.g., C. maschalocarpum and E. radiata ) and red algae (e.g., G. macrocarpa ) [2]. This included the polysaccharides alginate, laminarin and FCSP that are important constituents of brown algae [7, 8, 14, 15], as well as carrageenan, the major cell wall polysaccharide in Gigartina species [9]. This diverse and complex substrate landscape, stemming from the range of highly polymerized and decorated polysaccharides (heteropolysaccharides) in the fish diet, requires a complex cascade of enzymatic processes, which in turn demands greater genetic diversity than is present in a single organism [16].…”