Nutrient and heavy metal content of edible seaweeds in New Zealand

The nutritional composition of four commercially available seaweeds, Macrocystis pyrifera, Undaria pinnatifida, Porphyra and Ecklonia radiata , was compared with six wild‐harvested species, Ulva stenophylla, Porphyra, Ecklonia radiata, Durvillaea antarctica, Hormosira banksii and Undaria pinnatifida . In the wild‐collected species, ash contents were high (19.8–26.6% dry weight). Carbohydrate content ranged from 45.4–66.9%, while protein varied from 6.1–32.7%. Some species had high levels of potassium (<71.2 g/kg) and calcium (<15.3 g/kg). Total arsenic concentrations were high in some species (<97 mg/kg), but the dominant forms were the organic arsenic compounds that are regarded as non‐toxic. Inorganic arsenic was well below the New Zealand regulatory limit. The variation in proximate composition and mineral content was high among species collected at different times or locations and between different species. New Zealand's native and naturalized seaweeds are comparable to other edible seaweeds and would be a healthy addition to normal diets.