Assessment of contaminant concentrations and nutritional value of New Caledonian seaweeds

While the seaweed industry is developing worldwide, the untapped diversity of species in New Caledonia offers many opportunities for value-added products that can stimulate the local blue economy. However, human activities and the particular geology of the archipelago can release contaminants into the marine environment. Seaweeds bioaccumulate heavy metals and other contaminants from their growing environment, which can pose a significant food safety concern and a barrier to developing seaweed-based products. In this study, we measured heavy metals, metalloids, minerals, iodine, persistent organic pollutants, and pesticide residues in 17 species of interest. We assessed the nutritional benefits and health risks in accordance with current food safety regulations and calculated the Hazard Index. Our analyses revealed considerable variability across taxonomic groups, sites, and habitats. New Caledonian species can make significant contributions to daily requirements in several micro and macroelements. However, all our samples exceeded the European total arsenic maximum limit (for food additives), and half of the species exceeded the French recommendations for inorganic arsenic in seaweed-based products. A few samples exceeded the French recommendations for Cadmium, the maximum limit for Iodine, and the European maximum limit for some polycyclic aromatic hydrocarbons. Five species were identified as safe for consumption: Caulerpa oligophylla, Codium sp., Gracilaria salicornia, Ulva meridionalis, and Umbraulva kuaweuweu. Our study offers new data on contaminant concentrations across multiple species and establishes a health-based framework for selecting safe species and guiding their appropriate use in developing New Caledonia's seaweed industry.