Abstract
Undaria pinnatifida, Wakame is a popular edible seaweed in its native Asia and was first recorded in New Zealand in Wellington Harbor in 1987. It is classified as an unwanted species under the Biosecurity Act 1993, but there is growing interest in harvesting this seaweed for human consumption. The aim of this study was to evaluate the concentrations of metals in U. pinnatifida from several locations (Marlborough Sounds and Wellington harbor) and across seasons. In brief, the highest monthly mean concentration of metals found in New Zealand wild U. pinnatifida was Ca (16.97g·kg-1), K (48.48 g·kg-1), Mg (9.47 g·kg-1), P (12.05 g·kg-1), Cr (1.04 mg·kg-1), Cu (3.78 mg·kg-1), Mn (14.61 mg·kg-1), Ni (2.78 mg·kg-1), Se (0.83 mg·kg-1), Zn (35.03 mg·kg-1), As (46.71 mg·kg-1), Cd (2.91 mg·kg-1), Hg (0.042 mg·kg-1) and Pb (0.31 mg·kg-1). These results showed that New Zealand U. pinnatifida is a good source of the nutritionally important minerals calcium, magnesium, potassium and phosphorus. They also contained trace amounts of minerals such as chromium, copper, manganese, nickel, selenium and zinc. Contaminants such as arsenic, cadmium, mercury and lead were found at very low, safe, levels.
Highlights
The importance of health foods is becoming widely acknowledged and as a result the consumption of seaweed in Western countries has gradually increased
Our results demonstrate that U. pinnatifida contained variety of minerals and heavy metals and that these varied in content across the time period investigated
We have determined the amount of each metal contained in an average serving of Wakame seaweed salad
Summary
The importance of health foods is becoming widely acknowledged and as a result the consumption of seaweed in Western countries has gradually increased. Seaweeds have been employed as food and medicines for a long period of time in many Asian countries such as Japan, Korea, China, Vietnam, Indonesia and Taiwan [1]. Metal uptake occurs in two steps: The first is passive uptake; a surface reaction, where metals are absorbed by algal surfaces through electrostatic attraction to negative sites [4] [5]. This is independent of factors which influence the metabolism such as temperature, light, pH or age of the plant, but it is influenced by the relative abundance of elements in the surrounding water [4]. The second way metals can be taken up into seaweeds is a slower active uptake in which metal ions are transported across the cell membrane into the cytoplasm and is more dependent upon metabolic processes [4] [5]
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