Addition of iron does not ameliorate sulfide toxicity by sargassum influx to mangroves but dampens methane and nitrous oxide emissions.

Sargassum spp. strandings in the tropical Atlantic harm local ecosystems due to toxic sulfide levels. We conducted a mesocosm experiment to test the efficacy of iron(III) (hydr)oxides in (a) mitigating sulfide toxicity in mangroves resulting from Sargassum and (b) reducing potentially enhanced greenhouse gas emissions. Our results show that iron addition failed to prevent mangrove mortality caused by highly toxic sulfide concentrations, which reached up to 15,000 µmol l-1 in 14 days; timely removal may potentially prevent mangrove death. Sargassum-impacted mesocosms significantly increased methane, nitrous oxide, and carbon dioxide emissions, producing approximately 1 g CO2-equivalents m-2 h-1 during daylight hours, thereby shifting mangroves from sinks to sources of greenhouse gasses. However, iron addition decreased methane emissions by 62 % and nitrous oxide emissions by 57 %. This research reveals that Sargassum strandings have multiple adverse effects related to chemical and ecological dynamics in mangrove ecosystems, including greenhouse gas emissions.

Assessment of Silver Nanoparticles Derived from Brown Algae Sargassum vulgare: Insight into Antioxidants, Anticancer, Antibacterial and Hepatoprotective Effect.

Algae are used as safe materials to fabricate novel nanoparticles to treat some diseases. Marine brown alga Sargassum vulgare are used to fabricate silver nanoparticles (Sv/Ag-NPs). The characterization of Sv/Ag-NPs was determined by TEM, EDX, Zeta potential, XRD, and UV spectroscopy. The Sv/Ag-NPs were investigated as antioxidant, anticancer, and antibacterial activities against Gram-positive bacteria Bacillus mojavensis PP400982, Staphylococcus caprae PP401704, Staphylococcus capitis PP402689, and Staphylococcus epidermidis PP403851. The activity of the Sv/Ag-NPs was evaluated as hepatoprotective in vitro in comparison with silymarin. The UV-visible spectrum of Sv/Ag-NPs appeared at 442 nm; the size of Sv/Ag-NPs is in range between 6.90 to 16.97 nm, and spherical in shape. Different concentrations of Sv/Ag-NPs possessed antioxidant, anticancer activities against (HepG-2), colon carcinoma (HCT-116), cervical carcinoma (HeLa), and prostate carcinoma (PC-3) with IC50 50.46, 45.84, 78.42, and 100.39 µg/mL, respectively. The Sv/Ag-NPs induced the cell viability of Hep G2 cells and hepatocytes treated with carbon tetrachloride. The Sv/Ag-NPs exhibited antibacterial activities against Staphylococcus caprae PP401704, Staphylococcus capitis PP402689, and Staphylococcus epidermidis PP403851. This study strongly suggests the silver nanoparticles derived from Sargassum vulgare showed potential hepato-protective effect against carbon tetrachloride-induced liver cells, and could be used as anticancer and antibacterial activities.

Profile of inorganic elements of seaweed from the Brazilian Northeast coast.

The contents of 24 elements were determined in seven species of macroalgae collected in Ceara-Brazil, in the rainy and dry seasons of 2022. The samples were digested, and the analytes were quantified by ICP-OES and Hg by direct analyzer. The CRM CD-200 was analyzed for accuracy and obtained recoveries were higher than 95 %. The seaweed species have different inorganic element profiles with predominant elements being: Ca, K, Na, Mg and P. The Sargassum vulgare species stood out for its Hg and As contents (1.479 ± 0.005 mg kg-1 and 172 ± 6 mg kg-1, both in the rainy seasons). Ulva lactuca attracted attention for its high concentration of V (46.4 ± 3.4 mg kg-1, rainy season). In general, the elemental content levels in the macroalgae samples were higher in the rainy season. Long-term studies to comprehend the effect of seasonality on the elemental composition of seaweed must be carried out.

The inherent nature of N/P heteroatoms in Sargassum fusiforme seaweed biochar enhanced the nonradical activation of peroxymonosulfate for acetaminophen degradation in aquatic environments.

This study investigated the catalytic activity of biochar materials derived from algal biomass Sargassum fusiforme (S. fusiforme) for groundwater remediation. A facile single-step pyrolysis process was used to prepare S. fusiforme biochar (SFBCX), where x denotes pyrolysis temperatures (600 °C-900 °C). The surface characterization revealed that SFBC800 possesses intrinsic N and P heteroatoms. The optimum experimental condition for acetaminophen (AAP) degradation (>98.70%) was achieved in 60 min using 1.0 mM peroxymonosulfate (PMS), 100 mg L-1 SFBC800, and pH 5.8 (unadjusted). Moreover, the degradation rate constant (k) was evaluated by the pseudo-first-order kinetic model. The maximum degradation (>98.70%) of AAP was achieved within 60 min of oxidation. Subsequently, the k value was calculated to be 6.7 × 10-2 min-1. The scavenger tests showed that radical and nonradical processes are involved in the SFBC800/PMS system. Moreover, the formation of reactive oxygen species (ROS) in the SFBC800/PMS system was confirmed using electron spin resonance (ESR) spectroscopy. Intriguingly, both radical (O2•-, •OH, and SO4•-) and nonradical (1O2) ROS were formed in the SFBC800/PMS system. In addition, electrochemical studies were conducted to verify the electron transfer process of the nonradical mechanism in the SFBC800/PMS system. The scavenger and electron spin resonance (ESR) spectroscopy showed that singlet oxygen (1O2) is the predominant component in AAP degradation. Under optimal condition, the SFBC800/PMS system reached ∼81% mineralization of AAP within 5 min and continued to ∼85% achieved over 60 min of oxidation. Coexisting ions and different aqueous matrices were investigated to examine the feasibility of the catalyst system, and the SFBC800/PMS system was found to be effective in the remediation of AAP-contaminated groundwater, river water, and effluent water obtained from wastewater treatment plants. Moreover, the SFBC800-activated PMS system demonstrated reusability. Our findings indicate that the SFBC800 catalyst has excellent catalytic activity for AAP degradation in aquatic environments.

Sargassum spp. Ethanolic Extract Elicits Toxic Responses and Malformations in Zebrafish (Danio rerio) Embryos.

The amount of Sargassum spp. arriving in the Caribbean Sea has increased steadily in the last few years, producing a profound environmental impact on the ecological dynamics of the coasts of the Yucatan Peninsula. We characterized the toxicological effects of an ethanolic extract of Sargassum spp. on zebrafish (Danio rerio) embryos (ZFEs) in a 96-h static bioassay using T1 (0.01 mg/L), T2 (0.1 mg/L), T3 (1 mg/L), T4 (10 mg/L), T5 (25 mg/L), T6 (50 mg/L), T7 (75 mg/L), T8 (100 mg/L), T9 (200 mg/L), and T10 (400 mg/L). In this extract, we detected 74 compounds by gas chromatography-mass spectrometry (GC-MS), of which hexadecanoic acid methyl ester, and 2-pentanone 4-hydroxy-4-methyl, were the most abundant. In ZFEs, a median lethal concentration of 251 mg/L was estimated. Exposed embryos exhibited extensive morphological changes, including edema in the yolk sac, scoliosis, and loss of pigmentation, as well as malformations of the head, tail, and eyes. By integrating these abnormalities using the Integrated Biological Response (IBRv2) and General Morphological Score (GMS) indices, we were able to determine that ZFEs exposed to 200 mg/L (T9) exhibited the most pronounced biological response in comparison with the other groups. In the comparative transcriptomic analysis, 66 genes were upregulated, and 246 genes were downregulated in the group exposed to 200 mg/L compared with the control group. In the upregulated genes, we identified several gene ontology-enriched terms, such as response to xenobiotic stimuli, cellular response to chemical stimulus, transcriptional regulation, pigment metabolic process, erythrocyte differentiation and embryonic hemopoiesis, extracellular matrix organization, and chondrocyte differentiation involved in endochondral bone morphogenesis, among others. In the down-regulated genes, we found many genes associated with nervous system processes, sensory and visual perception, response to abiotic stimulus, and the nucleoside phosphate biosynthetic process. The probable connections among the morphological changes observed in the transcriptome are thoroughly discussed. Our findings suggest that Sargassum spp. exposure can induce a wide negative impact on zebrafish embryos. Environ Toxicol Chem 2024;43:1075-1089. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Survey of arsenic content in edible seaweeds and their health risk assessment.

Since humans are especially sensitive to arsenic exposure, predominantly through diet, a strict control of the most widely consumed seaweeds is mandatory. Total arsenic contents and arsenic species in twenty-five different seaweeds from five different origins were studied. Seaweeds selected, included Phaeophyta (brown seaweed), Chlorophyta (green seaweed) and Rhodophyta (red seaweed) genera. The highest arsenic content appears in the Phaeophyta seaweed in the range from 11 to 162 mg kg-1 dried weight. Arsenosugars were found to be the predominant species of arsenic in most seaweeds, being up to 99.7% of total arsenic in some samples. The arsenic dietary intakes for seaweeds studied were assessed and the Target Hazard Quotients (THQ) and the Target Cancer Risk (TCR) were calculated, taking into account inorganic arsenic contents (iAs). iAs species in seaweeds showed low risk of arsenic intake except for Hizikia fusiforme samples.

The Role of Sargahydroquinoic Acid and Sargachromenol in the Anti-Inflammatory Effect of Sargassum yezoense.

The anti-inflammatory effect of the ethanol extract of Sargassum yezoense and its fractions were investigated in this study. The ethanol extract exhibited a strong anti-inflammatory effect on lipopolysaccharide-stimulated RAW 264.7 macrophages and effectively suppressed the M1 polarization of murine bone-marrow-derived macrophages stimulated by lipopolysaccharides and IFN-γ (interferon-gamma). Through a liquid-liquid extraction process, five fractions (n-hexane, chloroform, ethyl acetate, butanol, and aqueous) were acquired. Among these fractions, the chloroform fraction (SYCF) was found to contain the highest concentration of phenolic compounds, along with two primary meroterpenoids, sargahydroquinoic acid (SHQA) and sargachromenol (SCM), and exhibit significant antioxidant capacity. It also demonstrated a robust anti-inflammatory effect. A direct comparison was conducted to assess the relative contribution of SHQA and SCM to the anti-inflammatory properties of SYCF. The concentrations of SHQA and SCM tested were determined based on their relative abundance in SYCF. SHQA contributed to a significant portion of the anti-inflammatory property of SYCF, while SCM played a limited role. These findings not only highlight the potential of the chloroform-ethanol fractionation approach for concentrating meroterpenoids in S. yezoense but also demonstrate that SHQA and other bioactive compounds work additively or synergistically to produce the potent anti-inflammatory effect of SYCF.

The Beneficial Roles of Sargassum spp. in Skin Disorders.

As the body's largest organ, the skin is located at the internal and external environment interface, serving as a line of defense against various harmful stressors. Recently, marine-derived physiologically active ingredients have attracted considerable attention in the cosmeceutical industry due to their beneficial effects on skin health. Sargassum, a genus of brown macroalgae, has traditionally been consumed as food and medicine in several countries and is rich in bioactive compounds such as meroterpenoids, sulfated polysaccharides, fucoidan, fucoxanthin, flavonoids, and terpenoids. Sargassum spp. have various beneficial effects on skin disorders. They help with atopic dermatitis by improving skin barrier protection and reducing inflammation. Several species show potential in treating acne by inhibiting bacterial growth and reducing inflammation. Some species, such as Sargassum horneri, demonstrate antiallergic effects by modulating mast cell activity. Certain Sargassum species exhibit anticancer activity by inhibiting tumor growth and promoting apoptosis, and some species help with wound healing by promoting angiogenesis and reducing oxidative stress. Overall, Sargassum spp. demonstrate potential for treating and managing various skin conditions. Therefore, the bioactive compounds of Sargassum spp. may be natural ingredients with a wide range of functional properties for preventing and treating skin disorders. The present review focused on the various biological effects of Sargassum extracts and derived compounds on skin disorders.

In vitro and in vivo anti-inflammatory properties of an active fucoidan fraction from Sargassum fusiforme and a fraction-based hydrogel.

In a previous study, we separated an active fucoidan (JHCF4) from acid-processed Sargassum fusiforme, then analyzed and confirmed its structure. In the present study, we investigated the potential anti-inflammatory properties of JHCF4 and a JHCF4-based hydrogel in vitro and in vivo. JHCF4 reliably inhibited nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages, with an IC50 of 22.35 µg/ml. Furthermore, JHCF4 attenuated the secretion of prostaglandin E2, tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6, indicating that JHCF4 regulates inflammatory reactions. In addition, JHCF4 downregulated iNOS and COX-2 and inhibited the activation of the MAPK pathway. According to further in vivo analyses, JHCF4 significantly reduced the generation of reactive oxygen species (ROS), NO production, and cell death in an LPS-induced zebrafish model, suggesting that JHCF4 exhibits anti-inflammatory effects. Additionally, a JHCF4-based hydrogel was developed, and its properties were evaluated. The hydrogel significantly decreased inflammatory and nociceptive responses in carrageenan (carr)-induced mouse paws by reducing the increase in paw thickness and decreasing neutrophil infiltration in the basal and subcutaneous layers of the toe epidermis. These results indicate that JHCF4 exhibits potential anti-inflammatory activity in vitro and in vivo and that JHCF4-based hydrogels have application prospects in the cosmetic and pharmaceutical fields.

Fucosterol isolated from Sargassum horneri attenuates allergic responses in immunoglobulin E/bovine serum albumin-stimulated mast cells and passive cutaneous anaphylaxis in mice.

Allergic diseases have become a serious problem worldwide and occur when the immune system overreacts to stimuli. Sargassum horneri is an edible marine brown alga with pharmacological relevance in treating various allergy-related conditions. Therefore, this study aimed to investigate the effect of fucosterol (FST) isolated from S. horneri on immunoglobulin E(IgE)/bovine serum albumin (BSA)-stimulated allergic reactions in mouse bone marrow-derived cultured mast cells (BMCMCs) and passive cutaneous anaphylaxis (PCA) in BALB/c mice. The in silico analysis results revealed the binding site modulatory potential of FST on the IgE and IgE-FcεRI complex. The findings of the study revealed that FST significantly suppressed the degranulation of IgE/BSA-stimulated BMCMCs by inhibiting the release of ß-hexosaminidase and histamine in a dose-dependent manner. In addition, FST effectively decreased the expression of FcεRI on the surface of BMCMCs and its IgE binding. FST dose-dependently downregulated the expression of allergy-related cytokines (interleukin (IL)-4, -5, -6, -13, tumor necrosis factor (TNF)-α, and a chemokine (thymus and activation-regulated chemokine (TARC)) by suppressing the activation of nuclear factor-κB (NF-κB) and Syk-LAT-ERK-Gab2 signaling in IgE/BSA-stimulated BMCMCs. As per the histological analysis results of the in vivo studies with IgE-mediated PCA in BALB/c mice, FST treatment effectively attenuated the PCA reactions. These findings suggest that FST has an immunopharmacological potential as a naturally available bioactive compound for treating allergic reactions.

Temporal fluctuation of metallic trace elements concentrations in three morphotypes of floating holopelagic Sargassum from the Caribbean coast (Guadeloupe, French West Indies).

Since 2011, the Caribbean coasts have unprecedented stranding of a pelagic brown macroalgae Sargassum inducing damages for coastal ecosystems and economy. This study evaluated the temporal fluctuations of metallic trace elements (MTE) in Sargassum freshly arrived on the Caribbean coast. From May 2020 to September 2021, 12 floating samples of three morphotypes (S. fluitans III and S. natans I and VIII) were regularly collected in the Petit Cul-de-Sac Marin (Guadeloupe, French West Indies). Measured concentrations of 28 metal(loid)s trace elements reveal i) an absence of seasonal patterns in MTE concentrations except for metals Fe and Al during 2020 summer ii) a regular and high As content during the entire survey iii) a similar trend of contamination for each morphotype. The constant and high amount of As implies that stranding management policy and valorization processes of Sargassum must consider As contamination and that this vigilance must be constantly along the year.

Microbial communities present in Sargassum spp. leachates from the Mexican Caribbean which are involved in their degradation in the environment, a tool to tackle the problem.

The Sargassum phenomenon is currently affecting the Caribbean in several ways; one of them is the increase of greenhouse gases due to the decomposition process of this macroalgae; these processes also produce large amounts of pollutant leachates, in which several microbial communities are involved. To understand these processes, we conducted a 150-day study on the Sargassum spp environmental degradation under outdoor conditions, during which leachates were collected at 0, 30, 90, and 150 days. Subsequently, a metagenomic study of the microorganisms found in the leachates was carried out, in which changes in the microbial community were observed over time. The results showed that anaerobic bacterial genera such as Thermofilum and Methanopyrus were predominant at the beginning of this study (0 and 30 days), degrading sugars of sulfur polymers such as fucoidan, but throughout the experiment, the microbial communities were changed also, with the genera Fischerella and Dolichospermum being the most predominant at days 90 and 150, respectively. A principal component analysis (PCA) indicated, with 94% variance, that genera were positively correlated at 30 and 90 days, but not with initial populations, indicating changes in community structure due to sargassum degradation were present. Finally, at 150 days, the leachate volume decreased by almost 50% and there was a higher abundance of the genera Desulfobacter and Dolichospemum. This is the first work carried out to understand the degradation of Sargassum spp, which will serve, together with other works, to understand and provide a solution to this serious environmental problem in the Caribbean.

Predominant heterotrophic diazotrophic bacteria are involved in Sargassum proliferation in the Great Atlantic Sargassum Belt.

Since 2011, the Caribbean coasts have been subject to episodic influxes of floating Sargassum seaweed of unprecedented magnitude originating from a new area "the Great Atlantic Sargassum Belt" (GASB), leading in episodic influxes and mass strandings of floating Sargassum. For the biofilm of both holopelagic and benthic Sargassum as well as in the surrounding waters, we characterized the main functional groups involved in the microbial nitrogen cycle. The abundance of genes representing nitrogen fixation (nifH), nitrification (amoA), and denitrification (nosZ) showed the predominance of diazotrophs, particularly within the GASB and the Sargasso Sea. In both location, the biofilm associated with holopelagic Sargassum harboured a more abundant proportion of diazotrophs than the surrounding water. The mean δ15N value of the GASB seaweed was very negative (-2.04‰), and lower than previously reported, reinforcing the hypothesis that the source of nitrogen comes from the nitrogen-fixing activity of diazotrophs within this new area of proliferation. Analysis of the diversity of diazotrophic communities revealed for the first time the predominance of heterotrophic diazotrophic bacteria belonging to the phylum Proteobacteria in holopelagic Sargassum biofilms. The nifH sequences belonging to Vibrio genus (Gammaproteobacteria) and Filomicrobium sp. (Alphaproteobacteria) were the most abundant and reached, respectively, up to 46.0% and 33.2% of the community. We highlighted the atmospheric origin of the nitrogen used during the growth of holopelagic Sargassum within the GASB and a contribution of heterotrophic nitrogen-fixing bacteria to a part of the Sargassum proliferation.

Pelagic Sargassum in the Gulf of Mexico driven by ocean currents and eddies.

Pelagic Sargassum in the Gulf of Mexico (GoM) plays an important role in ocean biology and ecology, yet our knowledge of its origins and transport pathways is limited. Here, using satellite observations of Sargassum areal density and ocean surface currents between 2000 and 2023, we show that large amounts of Sargassum in the GoM can either originate from the northwestern GoM or be a result of physical transport from the northwestern Caribbean Sea, both with specific transport pathways. Sargassum of the northwestern GoM can be transported to the eastern GoM by ocean currents and eddies, eventually entering the Sargasso Sea. Sargassum entering the GoM from the northwestern Caribbean Sea can be transported in three different directions, with the northward and eastward transports governed by the Loop Current System (LCS) and westward transport driven by the westward extension of the LCS, the propagation or relaying of ocean eddies, the wind-driven westward currents on the Campeche Bank with or without eddies, and the westward currents with/without currents associated with eddies in the northern/central GoM. Overall, the spatial distribution patterns of pelagic Sargassum in the GoM are strongly influenced by the LCS and relevant eddies.

Sperm-specific histone H1 in highly condensed sperm nucleus of Sargassum horneri.

Spermatogenesis is one of the most dramatic changes in cell differentiation. Remarkable chromatin condensation of the nucleus is observed in animal, plant, and algal sperm. Sperm nuclear basic proteins (SNBPs), such as protamine and sperm-specific histone, are involved in chromatin condensation of the sperm nucleus. Among brown algae, sperm of the oogamous Fucales algae have a condensed nucleus. However, the existence of sperm-specific SNBPs in Fucales algae was unclear. Here, we identified linker histone (histone H1) proteins in the sperm and analyzed changes in their gene expression pattern during spermatogenesis in Sargassum horneri. A search of transcriptomic data for histone H1 genes in showed six histone H1 genes, which we named ShH1.1a, ShH1b, ShH1.2, ShH1.3, ShH1.4, and ShH1.5. Analysis of SNBPs using SDS-PAGE and LC-MS/MS showed that sperm nuclei contain histone ShH1.2, ShH1.3, and ShH1.4 in addition to core histones. Both ShH1.2 and ShH1.3 genes were expressed in the vegetative thallus and the male and female receptacles (the organs producing antheridium or oogonium). Meanwhile, the ShH1.4 gene was expressed in the male receptacle but not in the vegetative thallus and female receptacles. From these results, ShH1.4 may be a sperm-specific histone H1 of S. horneri.

The Effects of Fucoidan Derived from Sargassum filipendula and Fucus vesiculosus on the Survival and Mineralisation of Osteogenic Progenitors.

Osteosarcoma is a bone cancer primarily affecting teenagers. It has a poor prognosis and diminished quality of life after treatment due to chemotherapy side effects, surgical complications and post-surgical osteoporosis risks. The sulphated polysaccharide fucoidan, derived from brown algae, has been a subject of interest for its potential anti-cancer properties and its impact on bone regeneration. This study explores the influence of crude, low-molecular-weight (LMW, 10-50 kDa), medium-molecular-weight (MMW, 50-100 kDa) and high-molecular-weight (HMW, >100 kDa) fractions from Sargassum filipendula, harvested from the Colombian sea coast, as well as crude fucoidan from Fucus vesiculosus, on a specific human osteoprogenitor cell type, human embryonic-derived mesenchymal stem cells. Fourier transform infrared spectroscopy coupled with attenuated total reflection (FTIR-ATR) results showed the highest sulphation levels and lowest uronic acid content in crude extract from F. vesiculosus. There was a dose-dependent drop in focal adhesion formation, proliferation and osteogenic differentiation of cells for all fucoidan types, but the least toxicity was observed for LMW and MMW. Transmission electron microscopy (TEM), JC-1 (5,50,6,60-tetrachloro-1,10,3,30-tetraethylbenzimi-dazolylcarbocyanine iodide) staining and cytochrome c analyses confirmed mitochondrial damage, swollen ER and upregulated autophagy due to fucoidans, with the highest severity in the case of F. vesiculosus fucoidan. Stress-induced apoptosis-like cell death by F. vesiculosus fucoidan and stress-induced necrosis-like cell death by S. filipendula fucoidans were also confirmed. LMW and MMW doses of <200 ng/mL were the least toxic and showed potential osteoinductivity. This research underscores the multifaceted impact of fucoidans on osteoprogenitor cells and highlights the delicate balance between potential therapeutic benefits and the challenges involved in using fucoidans for post-surgery treatments in patients with osteosarcoma.

Green Synthesis of Copper Nanoparticles Using Sargassum spp. for Electrochemical Reduction of CO2.

This study presents a green method of producing copper nanoparticles (CuNPs) using aqueous extracts from Sargassum spp. as reducing, stabilizing, and capping agents. The CuNPs created using this algae-based method are not hazardous, they are eco-friendly, and less toxic than their chemically synthesized counterparts. The XRD characterization of the CuNPs revealed the presence of Cu and CuO, with a crystallite size ranging from 13 to 17 nm. Following this, the CuNPs were supported onto a carbon substrate, also derived from Sargassum spp. (biochar CSKPH). The CuNPs in biochar (CuNPs-CSKPH) did not appear in the XRD diffractograms, but the SEM-EDS results showed that they accounted for 36 % of the copper weight. The voltamperometric study of CuNps-CSKPH in acid media validated the presence of Cu and the amount was determined to be 2.58 µg. The catalytic activity of CuNPs-CSKPH was analyzed for the electrochemical reduction of CO2. The use of Sargassum spp. has great potential to tackle two environmental problems simultaneously, by using it as raw material for the synthesis of activated biochar as support, as well as the synthesis of CuNPs, and secondly, by using it as a sustainable material for the electrochemical conversion of CO2.

Temporal and spatial variation in hydrogen sulfide (H2S) emissions during holopelagic Sargassum spp. decomposition on beaches.

BACKGROUND: Since 2011, over 30 tropical Atlantic nations have experienced substantial landings of holopelagic Sargassum spp. Its decomposition results in the production of hydrogen sulfide (H2S), which, in elevated concentrations, can pose a threat to human health. This study aims to enhance our understanding of the temporal and spatial variability in H2S emissions during the decomposition of Sargassum on beaches. The primary objective is to assess potential exposure risks for local populations, tourists, and cleanup workers. METHODS: H2S levels were monitored using a SENKO sensor (SGTP-H2S; limit of detection 0.1-100 ppm; resolution 0.1 ppm) at four distances from Sargassum accumulation points of (0, 10, 30, and 40 m) in Puerto Morelos, Mexico, during 2022 and 2023. RESULTS: Elevated concentrations of H2S were detected beneath the Sargassum piles, with 23.5% of readings exceeding 5 ppm and occasional spikes above 100 ppm. Above the piles, 87.3% of the measurements remained below 2 ppm, and the remainder fell between 2.1 and 5.2 ppm. At 10 m from the shoreline, 90% of measurements registered below 0.1 ppm, and the remaining 10% were below 2 ppm. Readings at 30 and 40 m consistently recorded levels below 0.1 ppm. H2S concentrations positively correlated with Sargassum pile height, the temperature beneath the piles, and wind speed. CONCLUSIONS: Our findings suggest no immediate and significant exposure risk for residents or tourists. However, Sargassum cleanup workers face a higher exposure risk, potentially encountering concentrations above 5 ppm for nearly one-fourth of the working time.

Sustainable synthesis of magnetic Sargassum siliquastrum activated carbon loaded with NiS nanorods for adsorption of 2,4-D herbicide.

The upgrade of sustainable resource waste into a valuable and beneficial material is an urgent task. The current paper outlines the development of an economical, sustainable, and prolonged adsorbent derived from Sargassum siliquastrum biomass and its use for potent 2,4-dichlorophenoxyacetic acid (2,4-D) removal. A simple carbonization approach was applied to obtain the highly functionalized carbon structure, which was subsequently transformed into a novel magnetic nanoadsorbent. The magnetic nanoadsorbent was characterized using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET)-specific surface area, and vibrating sample magnetometer (VSM). The characterization results confirm the successful formation of a high specific surface area and a uniform distribution of Fe3O4/NiS NPs grafted activated carbon. The adsorption kinetics was more accurately described via the pseudo-second order model; nevertheless, the isothermal data showed that the Langmuir model was most suitable. The monolayer adsorption capacity for 2,4-D was 208.26 ± 15.75 mg/g at 328 K. The favourability and spontaneity of the adsorption process were demonstrated by thermodynamic studies. The adsorbent displayed exceptional selectivity for 2,4-D and high stability in multi-cycle use. Electrostatic attraction, π-π stacking, and hydrogen bonding were all believed to have an impact on the sorbent's robust 2,4-D adsorption. Analyses of real tap and Nile River water samples showed little effect of the sample matrix on 2,4-D adsorption. This study presents an innovative approach for developing highly efficient adsorbent from natural biomass and offers an affordable way to recycle algal waste into beneficial materials.

Innovative spectral characterisation of beached pelagic sargassum towards remote estimation of biochemical and phenotypic properties.

In recent years, pelagic sargassum (S. fluitans and S. natans - henceforth sargassum) macroalgal blooms have become more frequent and larger with higher biomass in the Tropical Atlantic region. They have environmental and socio-economic impacts, particularly on coastal ecosystems, tourism, fisheries and aquaculture industries, and on public health. Despite these challenges, sargassum biomass has the potential to offer commercial opportunities in the blue economy, although, it is reliant on key chemical and physical characteristics of the sargassum for specific use. In this study, we aim to utilise remotely sensed spectral profiles to determine species/morphotypes at different decomposition stages and their biochemical composition to support monitoring and valorisation of sargassum. For this, we undertook dedicated field campaigns in Barbados and Ghana to collect, for the first time, in situ spectral measurements between 350 and 2500 nm using a Spectra Vista Corp (SVC) HR-1024i field spectrometer of pelagic sargassum stranded biomass. The spectral measurements were complemented by uncrewed aerial system surveys using a DJI Phantom 4 drone and a DJI P4 multispectral instrument. Using the ground and airborne datasets this research developed an operational framework for remote detection of beached sargassum; and created spectral profiles of species/morphotypes and decomposition maps to infer biochemical composition. We were able to identify some key spectral regions, including a consistent absorption feature (920-1080 nm) found in all of the sargassum morphotype spectral profiles; we also observed distinction between fresh and recently beached sargassum particularly around 900-1000 nm. This work can support pelagic sargassum management and contribute to effective utilisation of the sargassum biomass to ultimately alleviate some of the socio-economic impacts associated with this emerging environmental challenge.