Composition and bioaccessibility of elements in green seaweeds from fish pond aquaculture

The elemental composition of five species of green seaweeds (Chaetomorpha linum, Rhizoclonium riparium, Ulva intestinalis, Ulva lactuca, Ulva prolifera) grown in fish pond aquaculture systems were studied. The elemental bioaccessibility in these species was also investigated through the application of an innovative in vitro digestive model of the human gastrointestinal tract. It was observed that R. riparium had the highest levels of Mn, Sr, Cd, Sn, and I and that U. lactuca had the highest Ni and Cu concentrations. The daily amounts of dried green seaweed required for achieving specific dietary intakes were calculated, namely: 7g of dried U. lactuca (for meeting Cu Recommended Daily Allowance, RDA); 173g of dried U. lactuca (Zn RDA); 78g of dried C. linum (Se RDA); 41g of dried C. linum (Mo RDA); and 0.5g of dried R. riparium (I Dietary Reference Intake, DRI). Concerning elemental bioaccessibility, Mn and Cu had the highest values, always above 50%, I values were in the lower range, between 14 and 31%. The elemental bioaccessibility range of R. riparium (31-100%) was higher than the ranges for other species, particularly C. linum (0-56%). The bioaccessibility results entailed higher quantities of dried seaweed for reaching dietary intakes: 10g of dried U. lactuca (Cu RDA); 290g of dried R. riparium (Zn RDA); and 2g of dried R. riparium (I DRI). Accordingly, R. riparium is a very rich I source. This study showed the importance of taking into account bioaccessibility results in estimating dietary intakes.