Global drivers of variation in seaweed macronutrient composition and nutritional vale of selected seaweed species in northeastern New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
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2021
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Massey University
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Abstract
Seaweeds are taxonomically diverse and have many valuable commercial applications. Globally, the seaweed aquaculture sector is growing exponentially with promising ecological and environmental implications. While the nutritional characteristics of many commercial species are well-recognised, a vast proportion of seaweed taxa remains unexplored. Using a multivariate meta-analytic approach, I examine the reported nutritional composition of 182 seaweed species across 81 published studies using conventional proximate composition analyses to determine the relative amounts of ash, soluble carbohydrate, insoluble fibre, lipid, and protein. I found that although red seaweeds had higher nutritional value compared to brown and green seaweeds, minor differences separated the phyla. Furthermore, I found that procedural effects contributed strongly to variation in the reported values of specific macronutrients. Specifically, I discovered large among-study variation for reported insoluble fibre and soluble carbohydrate content and notable measurement error variation for reported lipid content. Additionally, I found nutritional trade-offs among seaweed species, where some species were higher (lower) in soluble carbohydrate and ash and lower (higher) in insoluble fibre and lipids. My meta-analysis revealed the scope of the impacts of among-study differences and insight into the expected relationships between macronutrients at the species level once procedural and phylum-level effects were accounted for. Unless standardized protocols are adopted, generalisations about the relative nutritional value of different seaweeds or seaweed taxa will be limited. Within northeastern New Zealand, I examined the nutritional composition of eleven coastal seaweeds using proximate composition analyses. On average, Asparagopsis armata and Pterocladiella capillacea were highest in protein, Corallina officinalis was highest in ash, and Xiphophora chondrophylla was highest in insoluble fibre. Additionally, Cystophora retroflexa was highest in lipids, Carpophyllum maschalocarpum was highest in soluble carbohydrates, and lastly, Codium fragile and Ulva lactuca were highest in moisture. Based on their higher protein contents, A. armata, and P. capillacea may be potentially important for New Zealand’s growing commercial seaweed industry. Overall, my thesis examining both large-scale seaweed nutritional composition and underlying variation as well as nutritional properties of northeastern New Zealand seaweeds provides insight into future directions for nutritional research on seaweeds and the implications for the development of seaweed aquaculture in New Zealand.