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Does Location Matter to the Giant Kelp? A comparison of nutritional composition and water quality of the giant kelp (Macrocystis pyrifera) when sampled off the coast of Australia and New Zealand.
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Abstract
The giant kelp (Macrocystis pyrifera) is one of the fastest growing seaweeds globally, at up to 60 cm per day
and plants reaching 50m. It is a positively buoyant species which grows up from the Ocean floor, enabling
the creation of ocean kelp forests. It is a native species to both New Zealand and Australia, is it also found
on the west coast of the US, South America, and South Africa. In the context of commercially grown
seaweeds the giant kelp is not utilised extensively in comparison to another brown seaweed species
Laminaria digitata. Previously reported Macrocystis pyrifera protein content values range from 9-17%
depending on location and environmental factors including the season of harvest. Protein sourced from
seaweed can contain all essential amino acids, and the protein profile of seaweeds is similar to egg protein.
Initial nutritional analysis using AOAC standard protocols of wild harvested fronds of Macrocystis pyrifera
from Tory Channel, South Island, New Zealand, found 12.2% dry weight (DW) crude protein, in comparison
only 6.5% DW from Tower Bay, Tasmania, Australia. Total fat values were similar at both sites with 1.9% DW
from New Zealand, and 1.2% and 1.4% DW from Australia. Macrocystis pyrifera usually has <2% fat content
year-round therefore these values are in the expected range. Interestingly, total polysaccharides varied
between sites with the New Zealand values at 21.6 mg / 100 g and the Australian samples at 21.8 mg / 100
g, and 35.3 mg / 100 g. Sampling was done at the same time of year in both locations, previous studies have
found higher growth rates for Macrocystis pyrifera on wave exposed sites potentially improving nutrient
uptake. This data sheds light on the how critical the location of aquaculture-based seaweed farms are when
creating optimal conditions for seaweed production and quality.