Abstract
The invasion of the brown seaweed Rugulopteryx okamurae is altering the equilibrium and reducing the biodiversity of marine coastal ecosystems of southern Europe, with negative economic consequences for fishermen, tourism and governments that regularly remove tons of arrivals from the coast. However, the large amount of biomass produced also implies an opportunity for the valorization of these seaweeds, for example, in the form of biofertilizer and/or biostimulant for agricultural use. In this study, we characterized the biochemical composition of Rugulopteryx okamurae and aqueous extracts elaborated from them. Their annual compositional variation was studied by measuring the concentration of carbohydrates, lipids, proteins, minerals, phenolic compounds, and antioxidant capacity, together with metals and micro/macro elements, in samples collected in two consecutive years from southern Spain. The composition of the algae varied between years for macro/micronutrients, metals, proteins, polyphenols and lipids (mainly terpenes), while polysaccharides (fucoidan, laminarin and alginate) remained in similar concentration. The seaweed composition highlighted for the terpene concentration mainly in 2023. The aqueous extracts significantly increased fucoidan and laminarin content respect to the seaweed. In all, the biochemical characterization conducted suggests that Rugulopteryx okamurae is valuable as a biofertilizer due to its mineral content, while the extract composition (sulfur, polyphenolics, fucoidan, laminarin, and glycolipids) suggests its potential use as biostimulant. Thus, this study proposes Rugulopteryx okamurae as a valuable waste for agricultural proposals.