Chemical Characterisation of Sargassum Inundation from the Turks and Caicos: Seasonal and Post Stranding Changes

Abstract

The Turks and Caicos Islands (TCI) have been affected by sargassum inundations, with impacts on the economy and environment. Sargassum removal can be costly, but sargassum use and valorisation may generate income and offset environmental damage. A significant barrier to the valorisation of sargassum is insufficient knowledge of its chemical makeup, as well as its seasonal variation and decay after stranding. The chemical characterisation of mixed sargassum and its constituent species and morphotypes (S. natans I, S.natans VIII and S. fluitans) collected from TCI between September 2020 and May 2021 and changes in the composition of sargassum decaying (over 147 days) were studied. High ash (24.61–51.10% dry weight (DW)) and arsenic (49–217 mg kg−1) could severely hamper the use of this seaweed for food or feed purposes. Although there was some reduction in arsenic levels in decaying sargassum, levels remained high (>49 mg kg−1). Biomethane production by anaerobic digestion (AD) is a potential option. Nevertheless, the exploitation of sargassum for biogas, either fresh or as it decays on the beach, is challenging due to low methane yields (<42% of theoretical potential). Pre-treatment or co-digestion with other waste may be options to improve yield. The metal sorption ability of sargassum, which can be problematic, makes biosorption of pollutants an option for further research.

Biosorption Potential of Sargassum for Removal of Aqueous Dye Solutions

“…Chemical characterisation of many Sargassum species showed that metal content (in particular arsenic) severely hampers the prospects of using Sargassum species for food or feed. However, this seaweed's high metal sorption ability could offer a feasible and economical approach for removing industrial heavy-metal-bearing wastewaters that require efficient and cost-effective treatment [40]. Other non-conventional low-cost adsorbents were reviewed by Rafatullah et al [41].…”

Science and policy lessons learned from a decade of adaptation to the emergent risk of sargassum proliferation across the tropical Atlantic

“…While many species of brown algae have been investigated for their composition and valorisation, most of what we know about these aspects of bloom forming pelagic sargassum, e.g. species, morphological types (morphotypes) and biomass composition, was published five to ten years after the initial arrival (in the tropical Atlantic) of pelagic sargassum [48][49][50][51][52][53][54]. Valorisation has been a relatively new dimension of sargassum science and policy.…”

“…Some technologies are small-scale and can be rolled out cheaply to create benefits for affected communities or entrepreneurs, e.g. small biogas digesters for biomethane production, or sargassum storage for compost production (ideally mixed with other plant material or biological wastes) [54,[63][64][65][66][67][68]. Other use options require investment in sargassum specific technology, e.g.…”

Free-swimming fauna associated with influxes of pelagic sargassum: Implications for management and harvesting

“…Sargassum influx events are now considered the new 'normal' for the region (Desrochers et al, 2020) and show a trend of increasing severity (The Sargassum Watch System (SaWS), 2022). As the region continues to adapt to this new reality, there has been a surge in research and publications on impacts (Milledge and Harvey, 2016;Ramlogan et al, 2017;van Tussenbroek et al, 2017;United Nations Environment Programme, 2018;Resiere et al, 2019), forecasting (Wang and Hu, 2017;Johnson et al, 2020;Marsh et al, 2021;Marsh et al, 2022), potential uses (Desrochers et al, 2020;Thompson et al, 2020;Amador-Castro et al, 2021;Oxenford et al, 2021;United Nations Environment Programme -Caribbean Environment Programme et al, 2021) and chemical composition (Devault et al, 2019;Davis et al, 2020;Nielsen et al, 2021;Devault et al, 2022;Tonon et al, 2022). Research into the sargassum phenomenon reveals considerable spatial and temporal complexities associated with management due to its transboundary nature and unpredictability (Cox et al, 2021).…”