Sargassum Biomass Research Articles

Optimization of hydrochar synthesis conditions for enhanced Cd(II) and Pb(II) adsorption in mono and multimetallic systems

The characterisation of hydrochars derived from Sargassum biomass collected along the Mexican Caribbean coast reveals their favourable morphology and chemical composition for incorporating metal ions, including Cd(II) and Pb(II). Among the synthesized materials, HCS-3, produced at 180 °C with a 2 h residence time, exhibited superior yield, specific area, carbon content, and capacity for removing Cd(II) and Pb(II). Adsorption equilibrium studies demonstrate the presence of adsorption processes during Cd(II) and Pb(II) retention on HCS-3, with adsorption capacities slightly exceeding 140 and 340 mg g⁻1, respectively. Notably, HCS-3 shows a greater affinity for Pb(II) over Cd(II) when both elements are present concurrently. The physicochemical analysis through FTIR spectroscopy, functional group analysis, point of zero charge determination, SEM/EDS, and other techniques evidenced that HCS-3 possesses favourable characteristics to serve as a heavy metal adsorbent. These findings underscore the efficacy of hydrochars from Sargassum biomass in removing heavy metals, suggesting their potential as superior adsorbents compared to traditional or novel materials, and advising its possible versatility for other pollutants. Utilizing these hydrochars could mitigate the economic and environmental impact of Sargassum biomass by repurposing it for valuable applications.

A Parallelized Climatological Drifter-Based Model of Sargassum Biomass Dynamics in the Tropical Atlantic

A Parallelized Climatological Drifter-Based Model of Sargassum Biomass Dynamics in the Tropical Atlantic

Bioprocess Design and Evaluation of Hydrothermal Hydrolysates from Sargassum sp. for Enhancing Arthrospira platensis Growth and Protein Content

The proliferation of Sargassum biomass in various coastal areas has led to environmental and socio-economic problems. However, due to their unique composition, these biomasses offer versatile applications, prompting research into their potential in third-generation biorefineries. In this study, the hydrothermal processing of Sargassum sp. was evaluated under specific conditions at 190 °C/50 min and 150 °C/30 min. The resulting hydrolysates (liquid phase) were used as alternative culture media for cultivation. Nine treatments for the cultivation of Arthrospira platensis were assessed, varying the concentration of hydrothermal hydrolysates (HH) at 190 °C/50 min: T1 (5% v/v), T2 (10% v/v), and T3 (15% v/v). T4 (5% v/v), T5 (10% v/v), and T6 (15% v/v), maintaining the same HH conditions, and with the addition of 0.7 g/L NaNO3; and treatments T7, T8, and T9 had concentrations of 5%, 10%, and 15% of HH, respectively, at 150 °C/30 min with the addition of 0.7 g/L NaNO3, respectively. Each treatment was inoculated with 15% (v/v) of A. platensis. Growth kinetics were performed by sampling every three days for 24 days. Quantification of soluble proteins was performed for the best conditions of biomass production. The microalgae demonstrated the ability to grow under mixotrophic medium conditions and to utilize the available carbon sources in the culture medium. Treatment 4 has the highest biomass, with an Xmax (g/L) of 1.94 ± 0.06 and a protein production of 24.17 ± 0.86% (w/w). Therefore, this microalgal biomass can be used in the food matrix according to the biorefinery concept.

Changes in holopelagic Sargassum spp. biomass composition across an unusual year

The year 2021 marked a decade of holopelagic sargassum (morphotypes Sargassum natans I and VIII, and Sargassum fluitans III) stranding on the Caribbean and West African coasts. Beaching of millions of tons of sargassum negatively impacts coastal ecosystems, economies, and human health. Additionally, the La Soufrière volcano erupted in St. Vincent in April 2021, at the start of the sargassum season. We investigated potential monthly variations in morphotype abundance and biomass composition of sargassum harvested in Jamaica and assessed the influence of processing methods (shade-drying vs. frozen samples) and of volcanic ash exposure on biochemical and elemental components. S. fluitans III was the most abundant morphotype across the year. Limited monthly variations were observed for key brown algal components (phlorotannins, fucoxanthin, and alginate). Shade-drying did not significantly alter the contents of proteins but affected levels of phlorotannins, fucoxanthin, mannitol, and alginate. Simulation of sargassum and volcanic ash drift combined with age statistics suggested that sargassum potentially shared the surface layer with ash for ~50 d, approximately 100 d before stranding in Jamaica. Integrated elemental analysis of volcanic ash, ambient seawater, and sargassum biomass showed that algae harvested from August had accumulated P, Al, Fe, Mn, Zn, and Ni, probably from the ash, and contained less As. This ash fingerprint confirmed the geographical origin and drift timescale of sargassum. Since environmental conditions and processing methods influence biomass composition, efforts should continue to improve understanding, forecasting, monitoring, and valorizing sargassum, particularly as strandings of sargassum show no sign of abating.

Continuous Sargassum monitoring across the Caribbean Sea and Central Atlantic using multi-sensor satellite observations

Recurrent transnational Sargassum blooms across the Caribbean Sea and Atlantic Ocean have received growing attention. Different multispectral sensors, including Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imager Radiometer Suite (VIIRS), and Ocean and Land Color Instrument (OLCI), have been used to map their distributions. However, the synergistic use of multi-sensor observations for high temporal resolution Sargassum monitoring is lacking. Here, by combining MODIS (on Aqua and Terra), VIIRS (on JPSS1 and SNPP), and OLCI (on Sentinel-3A and -3B) observations, 3-day mean Sargassum distributions were mapped across the Caribbean Sea and Central Atlantic. The Sargassum biomass densities were derived using the sensor-specific Alternative Floating Algae Index (AFAI)-biomass model, and the consistency between the six sensors was examined using MODIS Aqua as the reference sensor. Comparison of the Sargassum biomass derived from different sensors shows that they have strong linear correlations (R2 ≥ 0.95), demonstrating high consistency and continuity between the six-sensor observations. On average, the combined six-sensor datasets provide ∼1.6 times more valid observations compared to the MODIS-only dataset in 2021, enabling the generation of the 0.5° 3-day mean products over ∼90% of the study region. Such 0.5° 3-day mean products detected ∼10-20% more biomass in the bloom peak month (June 2021) compared to the monthly mean counterpart. Increasing the spatial resolution to 0.1°, the 3-day mean products can continuously monitor Sargassum dynamics with eddies and tropical cyclones, which cannot be well captured by single sensors. This study highlights that combining multiple polar-orbiting satellite observations can achieve 3-day gap-free monitoring of floating macroalgae dynamics in the Caribbean Sea and tropical Atlantic, thus facilitating the analyses of the bloom response to different environmental conditions and the prediction of future bloom events.

The influence of Sargassum biomass and thallus density on the recruitment of coral reef fishes

The influence of Sargassum biomass and thallus density on the recruitment of coral reef fishes

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.

FTIR-ATR chemometric analysis on pelagic Sargassum reveals chemical composition changes induced by cold sample transportation and sunlight radiation

The massive arrival of Sargassum biomass on the Caribbean coast is a potential raw material source that needs an assessment of its quality and preservation state. Thus, the present study aimed to investigate how pelagic Sargassum changes its chemical composition due to sample transportation, morphotype (S. natans I, S. natans VIII, and S. fluitans III), and exposure to open-air conditions during two months of outdoor conditions using Fourier Transform Infra-Red (IR) spectroscopy and chemometric analysis. The results demonstrate that cold transportation to the lab before flash-freezing caused sample degradation, characterized by mannitol consumption and the formation of anaerobic metabolism products. Multivariate analyses showed that the IR spectral zone with differences between S. natans and S. fluitans were in the same IR spectral regions related to sample degradation. In the two flash-freezing treatments, S. fluitans had the highest IR peak absorbance of mannitol and a lower absorbance for the carboxylic acids IR peak. Between S. natans morphotypes, S. natans I had the highest modification caused by the cold transportation to the lab. The decomposition under prolonged time (up to eight weeks) in open-air conditions demonstrated an increased absorbance on the IR bands of carboxylic acids in the first four weeks. In the sixth and eighth weeks, the IR signals of calcium carbonate increased more than those from organic matter. This study provides a better understanding of the importance of preserving the collected samples and how the decomposition dynamics of Sargassum species may impact the extraction of key compounds, e.g., alginate and mannitol.

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.

Effective adsorptive removal of a cationic dye from aqueous solutions using a biosorbent derived from Sargassum sp.

Abstract The present research evaluated the potential use of the macroalga Sargassum sp., which was modified with filamentous fungus Cunninghamella echinulata for the biosorption of methylene blue (MB) dye. The modified fungal biomass (FERsarg) was obtained through solid-state fermentation of enzyme (alginate lyase). The FERsarg showed a pHPZC of 7.9, a low mass loss, material micro/mesoporous, and the presence of hydroxyl, carboxylic, phenolic, and carbonyl functional groups. The influence of biomass dosage, solution pH, contact time, initial concentration, and temperature were evaluated for MB biosorption, and the best results were obtained at 2 g L-1 and pH 6. The kinetic study revealed a better fit for the pseudo-second-order model, while the Sips model best described the equilibrium experimental data. The equilibrium was reached within 180 min and showed qmax yielding of 115.49 mg g-1 at 323 K. The thermodynamic understanding of the present research revealed that the biosorbent exhibited spontaneous, exothermic, and physical nature for MB removal. The adsorptive mechanism shows that the process was controlled by electrostatic attraction. Also the feasibility of using residual fermented biomass as a potential adsorbent was applied and discussed, contributing to the concept of minimum waste generation, and supporting the concept of circular bioeconomy.

Hydrochar from Sargassum biomass for water remediation: Insights from synthesis and ibuprofen removal

Hydrochar from Sargassum biomass for water remediation: Insights from synthesis and ibuprofen removal

Antioxidant activities in holopelagic Sargassum species from the Mexican Caribbean: Temporal changes and intra-thallus variation

In the last decade, massive events of Sargassum influx have been reported causing ecological and economic damages. In this study, we evaluated the antioxidant potential of the holopelagic species S. fluitans, S. natans I, and S. natans VIII which arrived during 2018–2019 on the Mexican Caribbean coast. The monthly and intra-thallus variation of the total phenolic content (TPC) and antioxidant activity were determined in hydroethanolic extracts. The antioxidant potential was assessed using two free radical scavenging assays DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) and FRAP as ferric reducing antioxidant power assay. All Sargassum species showed radical scavenging and reducing power due to their polyphenol content, but also due to the presence of other antioxidant metabolites such as mannitol, alginate, and fucoidan as observed in the 13C NMR spectra. The antioxidant capacity and the TPC in all Sargassum species were enhanced in August 2018 and March–April 2019, coinciding with elevated seawater temperatures and the highest solar irradiances. For all the holopelagic Sargassum species, the highest TPC was obtained in the axes rather than in the vesicles or leaves. These results suggest that invasive Sargassum biomass in the Mexican Caribbean contains different compounds with antioxidant properties and could be considered a natural alternative to synthetic antioxidants, especially if collected in the summer months.

Comparative study on the valorization of Sargassum from the Mexican Caribbean coast and Gulf of California as an ingredient on healthy diets for shrimp farming

Sargassum biomass is a potential ingredient for aquaculture formulations due to its high nutritional value and availability, as it contains a variety of essential nutrients including proteins, carbohydrates, lipids, vitamins, antioxidants, fiber, and minerals, which are essential for aquatic growing, development and health parameters including digestibility and immune response against diseases. Therefore, in this work, five experimental diets were formulated considering 2.5 % and 5 % levels of inclusion of Sargassum spp. from the Mexican Caribbean coasts (SC), and from the Gulf of California (SG), and one reference diet as a control. The characterization of the raw material and the proximal analysis of the five diets were evaluated according to standard reference methods. A 35-day feeding trial was conducted using juvenile Litopenaeus vannamei showed a shrimp survival rate of 97 ± 6 % (p > 0.05) on SC. Excellent weight gain (WG) performance of SC and SG diets at 2.5 % of inclusion resulted in >10 % WG compared to the control. The specific activity of amylase, lipase, trypsin, and chymotrypsin showed a significant increase by including Sargassum in diets, compared with the reference diet. Incorporating Sargassum at 2.5 % in feed formulations for shrimps showed a great opportunity to use it as an ingredient and improved production yields. The digestion and absorption parameters were represented by the enzymatic activity in which the diets based on Sargassum spp. from the Mexican Caribbean coast (SC) have resulted in the best performance.

Inorganic arsenic in holopelagic Sargassum spp. stranded in the Mexican Caribbean: Seasonal variations and comparison with international regulations and guidelines

Due to the massive proliferation and stranding of holopelagic Sargassum spp. over the last decade, different strategies for the sustainable valorisation of Sargassum biomass have been explored and investigated. One limitation to the development of Sargassum biomass valorisation is related to its high arsenic (As) content. The toxicity of As depends on the chemical forms present and their oxidation or valence state, classified as inorganic and organic compounds, with the inorganic As compounds being much more toxic than the organic ones. The aim of the present study was to determine the inorganic arsenic (iAs) content in holopelagic Sargassum spp. for which almost no information on stranded biomass is available. In this study, we examined the iAs content in the three holopelagic Sargassum morphotypes collected over a seasonal cycle in 2018–2019. The iAs concentrations ranged from 12.7 to 62.9 mg kg−1, representing 14.1–81.7% of total arsenic (TotAs). The iAs content was compared between species and seasons and discussed in the context of existing international regulations and guidelines.

Sargassum macroalgae from Quintana Roo as raw material for the preparation of high-performance phosphate adsorbent from aqueous solutions

Currently, the large volumes of Sargassum biomass (Sgs) arriving on Caribbean coasts are a problem that must be solved quickly. One alternative is to obtain value-added products from Sgs. In this work, Sgs is demonstrated to be a high-performance Ca - bioadsorbent for phosphate removal by a heat pretreatment at 800 °C that produces biochar. According to XRD analysis, calcined Sgs (CSgs) have a composition of 43.68%, 40.51%, and 8.69% of Ca(OH)2, CaCO3, and CaO, making CSgs a promising material for phosphate removal and recovery. Results demonstrated that CSgs have a high capacity to adsorb P over a wide range of concentrations (25–1000 mg P/L). After P removal, at low P concentration, the adsorbent material is rich in apatite (Ca5(PO4)3OH), and at high P concentration, brushite (CaHPO4•2H2O) was the main P compound. The CSg reached a Qmax of 224.58 mg P/g, which is higher than other high-performance adsorbents reported in the literature. The phosphate adsorption mechanism was dominated by chemisorption, followed by precipitation according to the pseudo-second-order kinetic model. The solubility of P (74.5 wt%) in formic acid solution and the water-soluble P (24.8 wt%) for CSgs after P adsorption indicated that the final product presents the potential to be used as fertilizer for acid soils. This biomass's processability and high phosphate adsorption performance for P removal make CSgs a potential material for wastewater treatment, and subsequent use of these residues as fertilizer offers a circular economy solution to this problem.

Life Cycle Assessment Applied to End-of-Life Scenarios of Sargassum spp. for Application in Civil Construction

Environmental risks and vulnerabilities in coastal regions include the massive deposits of brown algae of the genus Sargassum in regions such as the Caribbean, Gulf of Mexico, and northern Brazil. Efforts have been made to turn this problem into an opportunity by seeking new uses for this biomass in the sectors of food, agriculture, health, biofuels, bioremediation, and civil construction. Thus, this study aimed to produce quantitative data for different end-of-life scenarios of the Sargassum algae, seeking for potential applications of this macroalgae in the civil construction sector. For this purpose, we conducted a life cycle assessment (LCA) study of the Sargassum algae, in its natural destination, and evaluated its potential impact. This evaluation was then compared to the possible impacts of alternatives to their end of life, such as landfill disposal, drying and grinding to use as fibers or particles, burning the biomass to generate energy and fly ash, using a consequential LCA and the indicators of the ReCiPe 2016 method. For each of the proposed scenarios, the functional unit of 1 kg of the three types of unprocessed Sargassum algae that are found in the Brazilian deposits (natans I, natans VIII, and fluitans) was considered separately, and also for a composition that is closer to that found in the Brazilian deposits (50% fluitans, 15% natans I, and 35% natans VIII). The results for both natural decomposition scenarios demonstrated a dominant contribution to the categories of impact for climate change, marine eutrophication, and land use, thus justifying the search for new initiatives for the use of the algae. The burning process showed a significant contribution to most of the indicators, with emphasis on the massive generation of particulate, inherent to the biomass burning process; however, it showed a reduction in the magnitude of climate change emissions from around 47% to less than 2%. Finally, the proposed scenario of processing Sargassum biomass to obtain particles presented prevalence of magnitude for potential impact in most of the proposed indicators, due to the processes with high electricity consumption, but keeping climate change emissions’ relative reduction from 47% to 6%. Thus, new studies may further investigate the potential of application of these materials in different products and components of civil construction.

Seasonal variation in morphotype composition of pelagic Sargassum influx events is linked to oceanic origin

The recent proliferation of pelagic Sargassum spp. in the Tropical Atlantic causes major ecological and socioeconomic impacts to the wider Caribbean when it washes ashore, with regional fisheries and tourism industries particularly affected. The Caribbean influxes have been tracked to a new bloom region known as the North Equatorial Recirculation Region (NERR) encompassing the area between the South Equatorial Current and the North Equatorial Counter Current and extending from Africa to South America. The vast biomass of Sargassum presents serious problems when it washes ashore but also represents significant commercial opportunities, especially with biofuel and fertilizer. The floating Sargassum mats are themselves diverse ecosystems that vary both in their biodiversity and biochemical attributes. Two major species (Sargassum fluitans and S. natans) have been identified as well as several distinguishable morphotypes of each. Oceanic mixing tends to blend the morphotypes together making it difficult to determine if there are regions of the NERR that favour bloom and growth of the distinct types. In this study, we quantify the species and morphotype composition of Sargassum strandings in Barbados and test if this is related to separate oceanic origins and routes travelled using a backtracking algorithm based on ocean drifter data. We found significant seasonal variation in the relative abundance of three morphotypes and this could be traced to two distinct easterly sub-origins and/or transport pathways; one area around 15° N that travels directly E–W across the Atlantic, and another area generally south of 10° N that takes a more meandering route coming close the coast of South America. These findings contribute towards our understanding of why the Tropical Atlantic bloom is presently occurring as well as towards addressing valorisation constraints surrounding variation in the supply of the three commonly occurring morphotypes.

Mapping and quantifying pelagic Sargassum in the Atlantic Ocean using multi-band medium-resolution satellite data and deep learning

Pelagic Sargassum in the Atlantic Ocean is an important habitat for marine animals, yet frequent and massive beaching events around the Caribbean Sea have caused many problems. Currently, both retrospective assessment and near real-time monitoring over synoptic scales rely on medium-resolution multi-band satellite imagery and algorithms based on the alternative floating algae index (AFAI) or its alternatives. Despite the success in assessing long-term bloom patterns and providing synoptic information in near real-time, two weaknesses still exist: 1) due to spatial resolution limitations and optical complexity from the ocean, there are often false positive detection in nearshore waters (up to 30 km from shoreline). These waters are currently masked to avoid providing false information, thus leading to data gaps in nearshore waters; 2) due to perturbations by cloud-adjacent straylight and cloud shadows, both false positive and false negative detections are often encountered. The current solution is to dilate the cloudmask to make the adjacent pixels invalid, thus leading to data loss. In this work, a computer deep-learning model based on the Res-UNet architecture, namely U-net, was developed to overcome these difficulties. The model was trained and validated using a total of 8518 medium-resolution “ground truth” images carefully prepared from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites. After accounting for subpixel Sargassum coverage, the over accuracy of the DL model, as measured by its F1 score, is ∼92.5% (without masking nearshore waters or cloud-adjacent pixels), which is higher than that of the current AFAI model (86.2% after masking nearshore waters and cloud-adjacent pixels). Application of the DL model to the 2021 MODIS data (a major Sargassum year) showed substantially improved valid data coverage (monthly increases of 20–34%) in both nearshore waters and offshore waters, and increased Sargassum biomass during the summer months (by 10–20%) from the entire Sargassum belt extending from the west Africa to the Gulf of Mexico. In the minor Sargassum year of 2016, the DL model led to an average increase of about 7% in Sargassum biomass. The DL model also appears to be applicable to the Visible Infrared Imaging Radiometer Suite (VIIRS) from the Suomi National Polar-orbiting Partnership (SNPP) satellite and the Ocean Land Colour Instrument (OLCI) onboard the Sentinel 3A and 3B satellites. Merging multi-sensor observations (including MODIS) resulted in substantially improved valid data coverage in daily to weekly composites, thus improving near real-time monitoring.

Valorization of Sargassum Biomass as Potential Material for the Remediation of Heavy-Metals-Contaminated Waters.

Sargassum algae has become a major environmental issue due to its abundance in the Pacific Ocean with hundreds of tons reaching the beaches of the Mexican Caribbean every year. This generates large quantities of decomposing organic matter that have a negative impact on the region's economy and ecosystems. Sargassum valorization has turned out to be a fundamental aspect to mitigate its environmental impact. This study proposes the use and application of untreated Sargassum biomass for the decontamination of waters polluted with lead (Pb) and cadmium (Cd) through single and binary adsorption tests. Physicochemical and textural properties examined by SEM, XRD, and FT-IR elucidated that Sargassum biomass is viable to be used as a potential environmental benign adsorbent, exhibiting Cd(II) and Pb(II) adsorption capacities as high as 240 mg g-1 and 350 mg g-1, respectively, outperforming conventionally used adsorbents. This is attributed to its morphology, favorable surface charge distribution, and the presence of -OH and -COH groups. A strong affinity between the biomass and metal pollutants was evidenced by a thermodynamics study, showing a spontaneous and endothermic process. This work sets a practical route for the utilization of the Sargassum biomass, demonstrating its applicability as a potential material for heavy-metal-polluted water remediation, making a substantial contribution to a circular economy system.

Microdebris Abundance, Distribution, and Ingestion by Sargassum-Associated Juvenile Fishes in the Gulf of Mexico

Holopelagic Sargassum is a critical nursery habitat for the early life stages of many marine fishes, including several federally managed species in the United States and Caribbean. Sargassum is often aggregated along surface convergence features where microdebris (synthetic, semi—synthetic, and naturally—derived particles size) have also been found in relatively high concentrations. In this study, we collected microdebris from Sargassum and adjacent open water habitats (in 2018), and juvenile fishes from Sargassum (in 2017 and 2018) in the northern Gulf of Mexico to quantify habitat—specific microdebris concentrations and the degree to which Sargassum—associated juvenile fishes ingest microdebris. Microdebris concentrations within Sargassum habitats were, on average, 180 times greater than those found within adjacent open water habitats. Microdebris concentrations decreased with distance from shore in both Sargassum and open water habitats, and generally increased with Sargassum biomass. Microdebris ingestion by juvenile (9–320 mm SL) fishes (n = 846) varied by year (all taxa: 24.7% in 2017; 14.7% in 2018) and by taxa, and generally decreased with distance from shore. Small fibers were the dominant type of microdebris observed in stomach contents. The structural complexity of Sargassum provides a mechanism for microdebris capture and concentration in surface waters. Since 2011, massive blooms of Sargassum have inundated regions in the central Atlantic Ocean and Caribbean Sea. The role of Sargassum as a microdebris “sink” has major implications for the transport of microdebris as Sargassum drifts within and across basins and eventually strands on beaches and coastal habitats, or subsides to benthic environments.