Even though seaweeds have been recognized as key players in the ocean-to-atmosphere transfer of iodine in other parts of the world, there is a complete lack of knowledge about iodine accumulation in seaweeds of the Arabian Gulf. Similarly, very little is known about fluorine in seaweeds, anywhere in the world. Given that the Arabian Gulf is of particular interest due to being an extreme environment, featuring some of the highest temperatures and salinities observed in any marine water body worldwide, this study endeavoured to conduct a preliminary survey of iodine and fluorine levels in 11 of the most common seaweed species in the region, supported by morphological and molecular (DNA barcode)-based identification. Iodine was determined by inductively-coupled plasma-mass spectrometry, while ion chromatography was employed for analysis of fluoride. Species surveyed included Iyengaria stellata, Padina boergesenii, Chondria sp.Dictyota dichotoma, Colpomenia sinuosa, Feldmannia indica,Codium papillatum, Sargassum ilicifolium, S. ilicifolium var. acaraeocarpum, Sargassum asperifolium and Sargassum aquifolium. The findings of S. ilicifolium and S. ilicifolium var. acaraeocarpum reported here are new records both for Kuwait and the Arabian Gulf. P. boergesenii and D. dichotoma are new records for Kuwait.

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The fatty acid (FA) compositions of ten seaweeds representative of Chlorophyta, Rhodophyta, and Ochrophyta from Kuwait in the Arabian Gulf region were determined and are discussed in the context of their potential nutritional perspectives for seaweed valorization. All the seaweeds had higher saturated fatty acid (SFA) and lower monounsaturated (MUFA) and polyunsaturated fatty acid (PUFA) contents than those typical of tropical environments. Palmitic, myristic, stearic, oleic, linoleic, α-linolenic, and stearidonic acids were the major FAs detected. Arachidonic, eicosapentaenoic, and docosahexaenoic acids were detected in minor amounts. Conserved fatty acid patterns revealed phylogenetic relationships among phyla, classes, and orders matching the molecular phylogenies at higher taxonomic ranks. Hierarchical clustering analyses clearly segregated different seaweeds (except Codium papillatum and Iyengaria stellata) into distinct groups based on their FA signatures. All but one species (Chondria sp.) had health-beneficial n6/n3 PUFAs (0.33:1–2.94:1) and atherogenic (0.80–2.52) and thrombogenic indices (0.61–5.17). However, low PUFA/SFA contents in most of the species (except Ulva spp.) may limit their utilization in the formulation of PUFA-rich functional foods. Ulva spp. had substantially high PUFAs with PUFA/SFA >0.4, n6/n3 (0.33–0.66) and atherogenic (0.80–1.15) and thrombogenic indices (0.49–0.72), providing substantial potential for their utilization in food and feed applications.

Even though seaweeds have been considered a nutrient-rich dietary source of minerals in other parts of the world, there is little knowledge about trace element accumulation in seaweeds of the Arabian Gulf. The Arabian Gulf is of particular interest due to being an extreme environment, as it features some of the highest temperatures and salinities observed in any marine waters in the world. This study determined the minerals contents using inductively-coupled plasma-mass spectrometry (ICP-MS) in 10 of the most common seaweeds of this region (Iyengaria stellata, Padina boergesenii, Chondria sp., Feldmannia indica, Codium papillatum, Sargassum aquifolium, Ulva chaugulii, Ulva tepida and Ulva sp.) supported by morphological and molecular (DNA barcode)-based identification. The finding of U. chaugulii reported here is a new record both for Kuwait and the Arabian Gulf. Most of the seaweeds were rich in essential minerals including Ca, Mg, Na, K, Fe and Zn and their contents were higher than those of other mineral-rich foods. Principal component analysis revealed species-specific distributions of minerals in seaweeds. U. tepida and I. stellata were found to be exceptionally rich in most of the macro- and trace elements along with low As and Se, and thus can be utilized for food and feed applications.

Many marine algae are strong accumulators of halogens. Commercial iodine production started by burning seaweeds in the 19th century. The high iodine content of certain seaweeds has potential pharmaceutical and nutritional applications. While the metabolism of iodine in brown algae is linked to oxidative metabolism, with iodide serving the function of an inorganic antioxidant protecting the cell and thallus surface against reactive oxygen species with implications for atmospheric and marine chemistry, rather little is known about the regulation and homoeostasis of other halogens in seaweeds in general and the ecological and biological role of marine algal halogenated metabolites (except for organohalogen secondary metabolites). The present review covers these areas, including the significance of seaweed-derived halogens and of halogens in general in the context of human diet and physiology. Furthermore, the understanding of interactions between halogenated compound production by algae and the environment, including anthropogenic impacts, effects on the ozone layer and global climate change, is reviewed together with the production of halogenated natural products by seaweeds and the potential of seaweeds as bioindicators for halogen radionuclides.