Sargassum Biomass Research Articles

Trace elements in pelagic Sargassum species in the Mexican Caribbean: Identification of key variables affecting arsenic accumulation in S. fluitans

Since 2014, the Mexican Caribbean beaches have received massive influxes of the brown seaweed Sargassum (S. fluitans III, S. natans I and S. natans VIII), causing serious ecological and economic effects. Concentrations of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) were determined over an annual cycle in pelagic Sargassum species from massive influxes into the Mexican Caribbean. The contribution of trace elements, polysaccharides (alginate and fucoidans), and their main functional groups (uronic acids and sulfate) to arsenic content in Sargassum fluitans — the most abundant species in the Sargassum influx — is discussed. Arsenic was recorded in all samples, yielding mean concentrations of 74.2 ± 2.84 mg kg−1. Significant differences were found between species for As, Cu, Fe, and Pb, but not for Cd and Zn; also, S. fluitans showed significant differences in metal content between seasons for all elements, as well as in alginate and uronic acids from fucoidan. The season of the year, copper, iron, uronic acids, and sulfate content in fucoidan were the main variables associated with arsenic accumulation in S. fluitans as evidenced with a Generalized Linear Model. Arsenic content in Sargassum biomass exceeded the maximum allowable level in the rainy season; therefore, the content of this trace element should be carefully monitored for safe usage of Sargassum biomass.

Satellite remote sensing of pelagic Sargassum macroalgae: The power of high resolution and deep learning

In recent years, massive blooms of pelagic Sargassum have occurred in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico, and satellite imagery have been used operationally to monitor and track the blooms. However, limited by the coarse resolution and other confounding factors, there is often a data gap in nearshore waters, and the uncertainties in the estimated Sargassum abundance in offshore waters are also unclear. Higher-resolution satellite data may overcome these limitations, yet such a potential is hindered by the lack of reliable methods to accurately detect and quantify Sargassum in an automatic fashion. Here, we address this challenge by combining large quantities of high-resolution satellite data with deep learning. Specifically, data from the Multispectral Instrument (MSI, 10–20 m), Operational Land Imager (OLI, 30 m), WorldView-II (WV-2, 2 m), and PlanetScope/Dove (3 m) are used with a deep convolution neural network (DCNN) to extract Sargassum features and quantify Sargassum biomass density or areal coverage. By utilizing the U-net architecture and the pre-trained weights from the VGG16 model, the DCNN (i.e., the VGGUnet model) can extract Sargassum features while discarding other confusing features (waves, currents, phytoplankton blooms, clouds, cloud shadows, or striping noise). For Sargassum biomass estimated from OLI and MSI images, results indicate an accuracy of ~92% and 90%, respectively, when evaluated using images from the same sensor. When Sargassum areal coverage is estimated from WV-2 and Dove images, there is an accuracy of ~98% and 82%, respectively. When different sensors are cross-compared, OLI reveals ~30% more Sargassum biomass than MODIS from 14 OLI images collected in the Caribbean Sea (path/row: 001/050) for their commonly viewed observable areas, and ~ 180% more Sargassum biomass than MSI (N = 15, path/row: 001/050); such differences appear systematic (R2 = 0.98 and 0.73, respectively). Compared to the quasi-simultaneous MSI, OLI, and MODIS images, Dove shows higher Sargassum coverage. Higher-resolution sensors tend to observe more Sargassum because they can detect smaller-scale features that are missed by the coarser-resolution sensors, although the difference varies with time and location. The morphological characteristics of Sargassum features from these high-resolution data are also reported to facilitate management actions. The findings here not only fill the knowledge gaps and coverage gaps from previous studies, but more importantly pave the road toward operational monitoring and tracking Sargassum features in nearshore waters.

Seasonal characterization and quantification of biomolecules from sargassum collected from Mexican Caribbean coast – A preliminary study as a step forward to blue economy

Since 2014, Mexican Caribbean coasts have experienced an atypical massive arrival of pelagic Sargassum accumulated on the shores triggers economic losses, public health problems, and ecosystem damaging near the coastline. Mechanical harvesting has been implemented ending in landfills. Since Sargassum algae represent abundant biomass in tropical regions of the world, it has shown potential as a feedstock to supply bioprocesses focused on obtaining high-value compounds and bioproducts. Nevertheless, there is a lack of data on the biochemical composition of Sargassum biomass from Mexican Caribbean coasts to propose valorization pathways. This study conducted a biochemical and elemental characterization of Sargassum biomass and compared, through statistical analysis, the effect of the season (dry and wet), place of collection (from the beach and shallow water), and method of extraction (Microwave-Assisted Extraction and Enzyme Assisted Extraction) on biomass composition. The biomass composition, expressed in dry weight basis, revealed 5–7% moisture content, 24–31 % ash, 2.6–3.8 % lipids, 1.8–7.0 %, total carbohydrates, 3–11 % total proteins, 1.5–2.31 mgGAg−1 total phenolic compounds (TPC), 2.7–2.9 kcal g−1 calorific power, and metals such as As (30–146.3 ppm), Fe (16.5–45 ppm), P (197–472 ppm). The most influential factor on the compositional content of Sargassum biomass was the season of the year, followed by the extraction method and the place of collection of Sargassum. These results will elucidate information on the biotechnological potential of Sargassum biomass from the Mexican Caribbean, contributing to sustainability challenges of the region, minimizing waste, and making the most of resources.

Fear effects and group size interact to shape herbivory on coral reefs

AbstractFear of predators (‘fear effects’) is an important determinant of foraging decisions by consumers across a range of ecosystems. Group size is one of the main behavioural mechanisms for mitigating fear effects while also providing foraging benefits to group members. Within coral reef ecosystems, fear effects have been shown to influence the feeding rates of herbivorous fishes, a key functional group that prevents macroalgal overgrowth. Yet, how fear effects and group size interact to shape macroalgal removal on coral reefs remains unclear.Here, we conducted field‐based experiments using models of a common piscivorous fish, the leopard coral grouperPlectropomus leopardusand a series of macroalgalSargassum ilicifoliumassays positioned at increasing distances from the models (1, 2, 3 and 4 m) on two coral reefs in Singapore to investigate how acute fear effects shape the intensity of herbivory, and whether these effects were influenced by variation in the group size of herbivorous fishes feeding on the assays.We found acute fear effects strongly influenced the foraging behaviour of herbivorous fishes over small spatial scales. Rates ofSargassumbiomass removal, feeding rates and the total number of individual feeding events were all lower near the predator model. These effects dissipated rapidly with increasing distance from the predator model and were undetectable at a distance of 4 m. We also found generally larger group sizes of herbivorous fishes further from the predator model, presumably reflecting decreased risk. Furthermore, the number of individual bites/event increased significantly with increasing group size for two common browsing fishes,Siganus virgatusandSiganus javus.Our findings highlight that acute fear effects influence the distribution and intensity of herbivory over small spatial scales. Fear effects also interacted with herbivore group size resulting in changes in the number of individual feeding events and bite rates that collectively shape the realized ecosystem function of macroalgal removal on coral reefs. Group size is an important context‐dependent factor that should be considered when examining fear effects on coral reefs.A freePlain Language Summarycan be found within the Supporting Information of this article.

Shifts in biomass and structure of habitat-formers across a latitudinal gradient.

Global patterns of plant biomass drive the distribution of much of the marine and terrestrial life on Earth. This is because their biomass and physical structure have important consequences for the communities they support by providing food and habitat. In terrestrial ecosystems, temperature is one of the major determinants of plant biomass and can influence plant and leaf morphology. In temperate marine systems, macroalgae are major habitat‐formers and commonly display highly variable morphology in response to local environmental conditions. Variation in their morphology, and thus habitat structure on temperate reefs, however, is poorly understood across large scales. In this study, we used a trait‐based approach to quantify morphological variability in subtidal rocky reefs dominated by the algal genus Sargassum along a latitudinal gradient, in southeastern Australia (~900 km). We tested whether large‐scale variation in sea surface temperature (SST), site exposure, and nutrient availability can predict algal biomass and individual morphology. We found Sargassum biomass declined with increasing maximum SST. We also found that individual morphology varied with abiotic ocean variables. Frond size and intraindividual variability in frond size decreased with increasing with distance from the equator, as SST decreased and nitrate concentration increased. The shape of fronds displayed no clear relationship with any of the abiotic variables measured. These results suggest climate change will cause significant changes to the structure of Sargassum habitats along the southeastern coast of Australia, resulting in an overall reduction in biomass and increase in the prevalence of thalli with large, highly variable fronds. Using a space‐for‐time approach means shifts in morphological trait values can be used as early warning signs of impending species declines and regime shifts. Consequently, by studying traits and how they change across large scales we can potentially predict and anticipate the impacts of environmental change on these communities.

Registro de arribazón inusual de Sargassum (Phaeophyceae) para la costa Atlántica de Costa Rica

Background: Since 2011, the coasts of North America, Mexico, and the Caribbean have experienced an unusual increase in the arrival of Sargassum. As a consequence of this massive accumulations of Sargassum holopelagic species in Caribbean Sea have been generated and that threaten local biodiversity and trigger economic losses associated with beach deterioration and impact on fisheries and tourism. Goals: This docu- ment quantifies the occurrence of an excessive drift of Sargassum in two sites (Puerto Viejo and Punta Uva) of the Caribbean coast of Costa Rica, Limon province, in March-April of 2019. A macroalgae species checklist is presented from six sites (Punta Cahuita, Puerto Vargas, Puerto Viejo, Playa Chiquita, Punta Uva and Manza- nillo) in the Caribbean. In addition, the Sargassum morphotypes are quantified for the study area. Methods: Transects (50 m) were located parallel to the shoreline and, in points previously estimated, a quadrat of 25 x 25 cm covered the entire Sargassum band width on the beach until the water line, by fliping the quadrats and collecting the biomass for as many quadrats were necessary for the band. Then, pelagic Sargassum biomass was weighted in every point, and the dry weight biomass was estimated. Three quadrats were collected by the transect method. Associated species were identified as well as Sargassum morphotypes in all sites. Results: Descriptions that illustrate the morphology of the three morphotypes of pelagic species. The putatively rare S. natans VIII dominated the dritf (65 % dry weight), followed by S. natans I (25% dry weight), and S. fluitans (10 % dry). Twenty eight species were identified from Chlorophyta (9), Ochrophyta (15), and Rhodophyta (4) Divisions. Conclusions: There were no signi- ficant differences between months (March-April) and sites (Puerto Viejo and Punta Uva) for the dritf biomass.

Evolution of the riverine nutrient export to the Tropical Atlantic over the last 15 years: is there a link with Sargassum proliferation?

The Tropical Atlantic is facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. As a contribution to this proliferation, an increase in nutrient inputs from the tropical rivers, in response to climate and land use changes or increasing urbanization, has been often suggested and widely reported in the scientific and public literature. Here we discuss whether changes in river nutrient inputs could contribute to Sargassum proliferation in the recent years or drive its seasonal cycle. Using long-term in situ and satellite measurements of discharge, dissolved and particulate nutrients of the three world largest rivers (Amazon, Orinoco, Congo), we do not find clear evidences that nutrient fluxes may have massively increased over the last 15 years. Moreover, focusing on year 2017, we estimate that along the year only 10% of the Sargassum biomass occurred in regions under river plume influence. While deforestation and pollution are a reality of great concern, our results corroborate recent findings that hydrological changes are not the first order drivers of Sargassum proliferation. Besides, satellite observations suggest that the major Atlantic river plumes suffered a decrease of phytoplankton biomass in the last two decades. Reconciling these observations requires a better understanding of the nutrient sources that sustain Sargassum and phytoplankton growth in the region.

Status, exploitation and resource management of alginophytes in India: an account and way forward

The biodiversity of Indian seaweeds comprises ca. 865 taxa, of which the alginophytes Sargassum spp., Cystoseira spp. and Turbinaria spp. are traditionally exploited. The alginate trade in India evolved as a cottage industry in the rural coastal regions of Tamil Nadu. The resource surveys have assured sufficient feed-stock availability, but landing data between 1978 and 2019 revealed a 54.85 and 33.59% decline in biomass of Sargassum spp. and Turbinaria spp., respectively. Despite this, alginate production continues to register incremental growth from 112 t in 2004–2005 to 262 t in 2018–2019. The higher production was due to feed-stock imported for domestic processing. Self-reliance in production can only be achieved by resource management and developing a viable farming protocol. This shall support sustainable trade by reducing dependency on wild harvesting. The complete valorisation of biomass by employing a high-throughput integrated bio-refinery protocol for sequential extraction of industrial products, viz. bio-stimulant, pigments, mannitol and alginates, is pivotal for profitable enterprise. Since the domestic industry is heavily depending on artisanal seaweed gatherers of the Gulf of Mannar, it is crucial to protect their rights by resolving issues pertaining to ownership of the resource coupled with conservation and sustainable utilisation. Seemingly, there is still a lot to be done on alginophytes in India. This review provides information and data on various domains of alginate trade aimed at developing a national programme and policy.

Biomass composition of the golden tide pelagic seaweeds Sargassum fluitans and S. natans (morphotypes I and VIII) to inform valorisation pathways

Massive strandings of the pelagic brown algae Sargassum have occurred in the Caribbean, and to a lesser extent, in western Africa, almost every year since 2011. These events have major environmental, health, and economic impacts in the affected countries. Once on the shore, Sargassum is mechanically harvested and disposed of in landfills. Existing commercial applications of other brown algae indicate that the pelagic Sargassum could constitute a valuable feedstock for potential valorisation. However, limited data on the composition of this Sargassum biomass was available to inform on possible application through pyrolysis or enzymatic fractionation of this feedstock. To fill this gap, we conducted a detailed comparative biochemical and elemental analysis of three pelagic Sargassum morphotypes identified so far as forming Atlantic blooms: Sargassum natans I (SnI), S. fluitans III (Sf), and S. natans VIII (SnVIII). Our results showed that SnVIII accumulated a lower quantity of metals and metalloids compared to SnI and Sf, but it contained higher amounts of phenolics and non-cellulosic polysaccharides. SnVIII also had more of the carbon storage compound mannitol. No differences in the content and composition of the cell wall polysaccharide alginate were identified among the three morphotypes. In addition, enzymatic saccharification of SnI produced more sugars compared to SnVIII and Sf. Due to high content of arsenic, the use of pelagic Sargassum is not recommended for nutritional purposes. In addition, low yields of alginate extracted from this biomass, compared with brown algae used for industrial production, limit its use as viable source of commercial alginates. Further work is needed to establish routes for future valorisation of pelagic Sargassum biomass.

Decadal characteristics of the floating Ulva and Sargassum in the Subei Shoal, Yellow Sea

The data of field surveys during 2009 to 2018 was analyzed to understand the seasonality and inter-annual variability of the floating Ulva and Sargassum in the Subei Shoal, the southwestern Yellow Sea of China on decadal scale. The floating Ulva biomass was consistently originated from the central region of the Subei Shoal in middle to late April, increased rapidly, drifted and extended into the offshore water in May and June. The average floating Ulva biomass in the shoal generally increased over the years with evident inter-annual fluctuations. In contrast, pelagic Sargassum was accumulated in the Subei Shoal and formed the spring bloom only in 2013, 2017 and 2018, and the biomass was higher than the co-occurring Ulva during the survey in these three years. Compared to the raft-origin floating Ulva, genesis and development of the pelagic Sargassum was distinct. Based on the current research, the Sargassum biomass was exotic and often initiated in the offshore water in March, and intruded into the shoal in April and May. The analysis on the environmental parameters was inconclusive since multiple anthropogenic and non-indigenous factors could influence the green tides in this region. Further research covering both the East China Sea and the Yellow Sea is needed to trace the origin of the floating Sargassum and to understand the interactions between these two co-occurring seaweeds.

Datasets on the optimization of alginate extraction from sargassum biomass using response surface methodology.

This article presents data associated with the extraction of sodium alginate from waste Sargassum seaweed in the Caribbean utilizing an optimization approach using Response Surface Methodology [1]. A Box-Behnken (BBD) Response Surface Methodology using Design Expert 10.0.3 software on the alkaline extraction process was used. Data consists of the effects of 4 process variables (temperature, extraction time, alkali concentration and excess volume of alkali: dried seaweed) on the yield of sodium alginate. The model was validated, and extracts were characterization using High Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The data illustrates the applicability of our model in potentially valorizing this waste product into a valuable resource. Furthermore, our methodology can be applied to other macroalgae for efficient extraction of sodium alginate of commercial quality.

Biosorption potential of Sargassum muticum algal biomass for methylene blue and lead removal from aqueous medium

In this examination, the proficiency of alga biomass Sargassum muticum for simultaneous uptake of methylene blue (MB) and lead (II) (Pb2+) ions from aqueous solution is investigated. The brown alga is surveyed by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption–desorption procedures. Impact of operating variables (brown alga mass, contact time and initial MB and Pb+2-ion concentration) on the simultaneous contaminants uptake is performed by means of central composite design and upgraded through response surface method (RSM). Accuracy of the equation procured by RSM is checked by the variance investigation and computing of determination coefficient (R2) among predicted and the experimental values of simultaneous noxious substances removal. Bon accord among empirical and envisaged values is commented. The optimum conditions are settled at contact time (30 min), 39 mg L−1 for MB and 30 mg L−1 for Pb2+ ions and brown alga mass (0.3 g) to reach maximum retention percentage. Adsorption kinetic depicted three phases intra-particle diffusion mode and coordinated the pseudo-second-order design very well. Batch equilibrium results reveal that MB and Pb2+ ions biosorption onto alga biomass could be all around portrayed by Langmuir isotherm model contrasted with Freundlich approach. In any case, removal percentage elaborated from column studies is inferior to those computed from batch technique. Column can be recouped and reutilized even after 5-adsorption–desorption cycles. X-ray photoelectron spectroscopy and FTIR scrutinies uncovered that hydroxyl, carbonyl and amino functional groups are responsible for the biosorption of both pollutants onto non-living brown alga. Previous tests achieved on paint wastewater demonstrated that the invasive biomass Sargassum muticum could be an effective and promising biosorbent for dye/metal wastewater treatment.

Sargassum epifaunal communities vary with canopy size, predator biomass and seascape setting within a fringing coral reef ecosystem

Tropical seascapes are comprised of a range of patch habitat types, yet we have only a partial understanding of how local patch condition and seascape position may influence patterns of marine biodiversity, particularly for invertebrate taxa. We investigated how the epifaunal abundance and biomass of tropical Sargassum varied with canopy size (volume, total length and dry weight), local patch conditions (macroalgal composition, canopy structure and invertivorous fish biomass) and seascape setting (nearshore, lagoon and back reef) within the Ningaloo fringing reef ecosystem, Australia. A total of 49431 epifauna, dominated by crustaceans and molluscs, were extracted from the thalli of 81 tropical Sargassum polycystum individuals. Epifaunal abundance and biomass were most strongly correlated with host Sargassum canopy volume and dry weight, respectively. Epifaunal abundance and biomass also varied significantly among separate Sargassum meadow patches, with a significant interaction between canopy size and seascape position. Considerable site-level variations in epifaunal biomass density (mg per g Sargassum dry weight) were best predicted by either seascape context or local invertivorous fish biomass. Sargassum within meadows furthest from the back reef tended to have the highest epifaunal biomass (dominated by molluscs), while meadows closest to the back reef were dominated by crustacea. Sargassum within meadows with a high local abundance of invertivorous labrids and serranids tended to have the lowest epifaunal biomass. Strong Sargassum canopy size-epifauna relationships indicate that even small differences in canopy extent have major flow-on effects for the trophic function of tropical marine ecosystems by affecting the epifaunal secondary productivity available to higher-order consumers, such as fishes.

Population Dynamics of the ‘Golden Tides’ Seaweed, Sargassum horneri, on the Southwestern Coast of Korea: The Extent and Formation of Golden Tides

Since 2015, troublesome masses of floating Sargassum horneri have been introduced via ocean currents and winds to the southwestern coastline of Korea, including Jeju Island. These massive mats have caused considerable damage to the aquaculture industry, tourism, and the marine ecosystem. Most previous studies of S. horneri have focused on cultivation, the development of gene markers, and photosynthetic activity, but few data on population dynamics are available. We investigated the population dynamics of native S. horneri off the southwestern coast of Korea with the aim of predicting the formation of golden tides. Populations at two sites had obligate annual life cycles. Thalli were recruited during the period September–November, grew during the period December–April, and senesced by July. This pattern reflected seasonal trends in water temperature. Specific growth rates and heights of the thalli at Munseom were significantly higher than those at Jindo. The greatest environmental difference between the two sites is probably the degree of exposure to wave action. Mortality density (thalli lost per unit area) in the Munseom population was highest during the period December–January (i.e., 2–3 months after recruitment) and in March. Most thalli in the Jindo population died off in July when water temperatures increased. The maximum average biomass of S. horneri thalli detaching from the substrata reached 1.6 kg fresh weight m–2 during January and March. Thus, large-scale drifting mats were formed by S. horneri detachment from the substrata. Despite the differences in space and environment between China and Korea, our findings will enable quantitative assessments of the overall floating Sargassum biomass in the East China and Yellow Seas.

Comparative kinetic analysis of alginate lyase and mannanase co-produced via solid-state fermentation of cow dung supplemented with seaweed wastes by a novel Streptomyces sp. Alg-S23

The global industrial interest in the application of biocatalysts to manufacture green and sustainable chemicals necessitates cost-effective production of microbial enzymes via screening out potent microbial isolates from different environmental niches and identifying cheap feedstocks for their propagation. In this study, the biocatalytic efficacy of a novel Streptomyces sp. Alg-S23 (GenBank accession no. MK098188) isolated from putrefying Sargassum seaweed waste was assessed for the first time for co-production of alginate lyase and mannanase via solid-state fermentation of cow dung supplemented with decomposed Sargassum as the feedstocks. The optimization of the SSF feedstock components by using a 22-factorial central composite statistical design resulted in the enhanced co-production of alginate lyase and mannanase at 15 g of cow dung and 4.5 g of decomposed Sargassum biomass. Maximal activities of extracted alginate lyase and mannanase were recorded at pH 7.5 and at temperature 50 °C and 55 °C, respectively. The co-produced alginate lyase and mannanase had strong affinity toward the substrate by displaying Km and Vmax values as 0.72 mg/mL and 10.2 U/mg-protein, and 1.83 mg/mL and 78.7 U/mg-protein, respectively. Thermal denaturation kinetic analysis of the co-produced alginate lyase and mannanase at 40-60 °C suggested that both the enzymes were thermodynamically efficient by exhibiting higher values of activation, enthalpy, and free energies of denaturation. These promising enzymatic traits highlight the novel potential of cow dung supplemented with decomposed Sargassum seaweed waste as the inexpensive feedstocks for sustainable production of alginate lyase and mannanase.

Decadal losses of canopy-forming algae along the warm temperate coastline of Brazil.

The loss of canopy-forming seaweeds from urbanized coasts has intensified in response to warming seas and non-climatic pressures such as population growth and declining water quality. Surprisingly, there has been little information on the extent of historical losses in the South-western Atlantic, which limits our ability to place this large marine ecosystem in a global context. Here, we use meta-analysis to examine long-term (1969-2017) changes to the cover and biomass of Sargassum spp. and structurally simple algal turfs along more than 1,000 kilometres of Brazil's warm temperate coastline. Analysis revealed major declines in canopy cover that were independent of season (i.e., displaying similar trends for both summer and winter) but varied with coastal environmental setting, whereby sheltered bays experienced greater losses than coastal locations. On average, covers of Sargassum spp. declined by 2.6% per year, to show overall losses of 52% since records began (ranging from 20% to 89%). This contrasted with increases in the cover of filamentous turfs (24% over the last 27years) which are known to proliferate along human-impacted coasts. To test the relative influence of climatic versus non-climatic factors as drivers of this apparent canopy-to-turf shift, we examined how well regional warming trends (decadal changes to sea surface temperature) and local proxies of coastal urbanization (population density, thermal pollution, turbidity and nutrient inputs) were able to predict the changes in seaweed communities. Our results revealed that the most pronounced canopy losses over the past 50years were at sites exhibiting the greatest degree of coastal warming, the highest population growth and those located in semi-enclosed sheltered bays. These findings contribute knowledge on the drivers of canopy loss in the South-western Atlantic and join with global efforts to understand and mitigate declines of marine keystone species.

Sargassum Seaweed as a Source of Anti-Inflammatory Substances and the Potential Insight of the Tropical Species: A Review.

Sargassum is recognized both empirically and scientifically as a potential anti-inflammatory agent. Inflammation is an important response in the body that helps to overcome various challenges to body homeostasis such as microbial infections, tissue stress, and certain injuries. Excessive and uncontrolled inflammatory conditions can affect the pathogenesis of various diseases. This review aims to explore the potential of Sargassum’s anti-inflammatory activity, not only in crude extracts but also in sulfated polysaccharides and purified compounds. The tropical region has a promising availability of Sargassum biomass because its climate allows for the optimal growth of seaweed throughout the year. This is important for its commercial utilization as functional ingredients for both food and non-food applications. To the best of our knowledge, studies related to Sargassum’s anti-inflammatory activity are still dominated by subtropical species. Studies on tropical Sargassum are mainly focused on the polysaccharides group, though there are some other potentially bioactive compounds such as polyphenols, terpenoids, fucoxanthin, fatty acids and their derivatives, typical polar lipids, and other groups. Information on the modulation mechanism of Sargassum’s bioactive compounds on the inflammatory response is also discussed here, but specific mechanisms related to the interaction between bioactive compounds and targets in cells still need to be further studied.

Spatial-Temporal Distribution of Golden Tide Based on High-Resolution Satellite Remote Sensing in the South Yellow Sea

Chen, Y.-L.; Wan, J.-H.; Zhang, J.; Ma, Y.-J.; Wang, L.; Zhao, J.-H., and Wang, Z.-Z., 2019. Spatial-temporal distribution of golden tide based on high-resolution satellite remote sensing in the South Yellow Sea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 221-227. Coconut Creek (Florida), ISSN 0749-0208.A new marine ecological disaster called the golden tide occurred in the Southern Yellow Sea at the end of 2016. This disaster damaged the Porphyra yezoensis aquaculture in the Jiangsu Shoal, causing a direct economic loss of nearly 500 million CNY. The floating brown macroalgae in the golden tide was identified as Sargassum horneri, which have been frequently growing in coastal waters in recent years. Effectively detecting this golden tide using traditional satellites is difficult because of the small patches or slicks of bloom. This study used multi-source and high-resolution satellite data to identify the floating Sargassum with a maximum multispectral resolution of 4 m (GF-2). Satellite and in-situ spectral data were used to analyze the spectral characteristics of the Sargassum and compare them with those of Ulva. Both sets of spectral characteristics exhibited the “red-edge” effect, and the difference was obvious between the green and red bands. Combined with the normalized difference vegetation index algorithm, monitoring and backtracking were performed for the golden tide disaster. Results show that the golden tide originated from the Rongcheng–Haiyang sea area of the Shandong peninsula and drifted to the south and westward. In early December 2016, Sargassum affected the sea area of Yancheng in Jiangsu Province. In late December 2016, it arrived at the Jiangsu Shoal and finally entered the Yangtze River estuary around mid-January 2017. The drifting path was mainly controlled by wind vector products. A comprehensive analysis of environmental factors showed that the sea surface temperature and chlorophyll-a in the South Yellow Sea were higher than normal during the golden tide disaster, which may be attributed to the rapid growth of the Sargassum biomass. Therefore, this study hypothesizes that an internal cause exists between the golden tide and the abovementioned factors

Factors Affecting the Distribution, Biomass, and Life Stages of Sargassum spp. in the Northwest Arabian Gulf

The developmental stages of Sargassum along with physicochemical factors affect the Sargassum biomass and, thus, affect the size of the habitat used by various fauna and flora. In this study, Sargassum spp. were collected from four stations in Kuwait coastal waters that are mainly distinguished by their levels of turbidity. Investigations revealed that the effects of season (i.e., temperature and sunlight) and turbidity on differences in Sargassum biomass were significant (chi-square = 6.1, degrees of freedom (df) = 2, p = 0.048), but the effects of Sargassum species (chi-square = 5.4, df = 2, p = 0.067) and their life stages (chi-square = 6.73, df = 4, p = 0.15) on Sargassum biomass were not significant. The lack of significant effects of Sargassum spp. on biomass could be because the majority of the collected Sargassum are of one species, S. angustifolium. As for the effect of life stages on Sargassum biomass, this could be because the majority of the stages encountered are juveniles or spent, which are found almost equally among all species. These stages were encountered particularly in spring and summer, mainly at the medium- and low-turbidity stations. The distribution of Sargassum spp. showed strong localization, in which the species inhabiting high-turbidity stations were different from those inhabiting clear waters. This study revealed that the effects of season and turbidity on Sargassum spp. and their life stages on Sargassum biomass represent a reference point for further monitoring studies in northwestern Arabian Gulf.

Remote Sensing of Sargassum Biomass, Nutrients, and Pigments

AbstractField and laboratory experiments are designed to measure Sargassum biomass per area (density), surface reflectance, nutrient contents, and pigment concentrations. An alternative floating algae index‐biomass density model is established to link the spectral reflectance to Sargassum biomass density, with a relative uncertainty of ~12%. Monthly mean integrated Sargassum biomass in the Caribbean Sea and central West Atlantic reached at least 4.4 million tons in July 2015. The average %C, %N, and %P per dry weight are 27.16, 1.06, and 0.10, respectively. The mean chlorophyll‐a (Chl‐a) concentration is ~0.05% of the dry weight. With these parameters, the amounts of nutrients and pigments can be estimated directly from remotely sensed Sargassum biomass. During bloom seasons, Sargassum carbon can account for ~18% of the total particulate organic carbon in the upper water column. This study provides the first quantitative assessment of the overall Sargassum biomass, nutrients, and pigment abundance from remote sensing observations, thus helping to quantify their ecological roles and facilitate management decisions.