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Where to grow the Giant Kelp? “Nutritional composition of wild harvested giant kelp compared"
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Abstract
The giant Kelp (Macrocystis pyrifera) is one of the fastest growing seaweeds globally with growth rates
of up to 60 cm per day. It is a positively buoyant species enabling the creation of kelp forests - a critical
ecosystem in the ocean. Macrocystis pyrifera communities have been lost in recent decades off the coast
of Australia, and since 2012 this species is listed as a threatened ecological community. It is also a native
species to New Zealand and found on the west coast of the US, South America, and South Africa.
The protein content of Macrocystis pyrifera ranges from 9-17% dry weight and depends on factors
including, location, environmental factors and harvest season. Protein obtained from seaweed contain all
the 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. Macrocystis pyrifera from Tower
Bay, Tasmania, Australia contained only 6.5% protein based on DW. 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 kelp found to contain 21.6 mg / 100 g
polysaccharides and the Australian samples 21.8 mg / 100 g, and 35.3 mg / 100 g, respectively. Previous
studies have found higher growth rates for this species on wave-exposed sites that can impact positively
nutrient uptake specifically in low nitrogen environments. This data suggests that such wave-exposed
locations are worth investigating for aquaculture-based seaweed farms, to enable optimal conditions for
seaweed production and quality, within a changing climate.