Beaching Events Research Articles

Unusual holopelagic Sargassum mass beaching in Northwest Africa: Morphotypes, chemical composition, and potential valorisation

The rapid proliferation of holopelagic Sargassum spp. in the tropical Atlantic Ocean presents environmental challenges and economic opportunities. In 2022, Senegal witnessed its first significant holopelagic Sargassum beaching event, triggering widespread concern and interest from civil society, industrial sectors, and government. This study represents the first analysis of stranded holopelagic Sargassum's morphotypes and chemical composition in Northwest Africa. We highlight the nature of Sargassum stranding, dominated by S. fluitans III, and describe a putative new morphotype. Compared to most of the studies in the tropical Atlantic, Senegalese Sargassum displayed lower arsenic concentrations (9–29 ppm), higher cadmium levels (9–15 ppm), and increased mercury content (0.47–0.57 ppm). In addition, Senegalese Sargassum showed higher levels of iron (237–1017 ppm) and phosphorus (1300–1772 ppm). The biochemical analysis revealed high total protein levels (15–40 % DW) in Senegalese samples, though further analysis is required to confirm this. Furthermore, variations in biochemical composition within various parts of the Sargassum thallus were observed. The low arsenic content makes the beached Senegalese Sargassum attractive for valorisation and sets it apart from holopelagic Sargassum from all other regions where it occurs. However, caution should be taken regarding the high concentrations of cadmium. Our study highlights promising applications in Senegal and neighbouring countries, particularly in animal feed and agriculture. Noteworthy is the notable palladium content (2 ppm), valuable phenolic compounds, and mannitol, which present additional opportunities for the chemical industry. Our interdisciplinary approach enhances the global scientific understanding of the Sargassum issue. With the anticipation of more frequent Sargassum beaching events and, more generally, for seaweed exploitation, we advocate for inter-governmental African organisations to establish standardised norms for their exploitation. We recommend that the Food and Agriculture Organization/World Health Organization consider incorporating more seaweed in the Codex Alimentarius to facilitate their uses particularly when states deal with algal blooms.

Where does floating Sargassum in the East China Sea come from?

Floating macroalgae of Sargassum horneri (S. horneri) in the East China Sea (ECS) has increased in recent years, with ocean warming being one of the driving factors. Yet their possible origins, based on a literature review, are unclear. Here, using multi-sensor high-resolution remote sensing data and numerical experiments for the period of 2015–2023, we show two possible origins of the ECS floating S. horneri, one being local near the Zhejiang coast with initiation in January–February and the other being remote (> 800 km from the first) in the Bohai Sea with initiation in June–November. While their drifting pathways are revealed in the sequential remote sensing imagery, numerical experiments suggest that S. horneri from the remote origin (Bohai Sea) can hardly meander through the strong Yangtze River frontal zone, which may serve as a “wall” to prevent trespassing of surface floating seaweed to the south of the frontal zone, where S. horneri has a local origin. Plain language summarySargassum horneri (S. horneri) is a brown macroalgae (seaweed) abundant in surface waters of the East China Sea (ECS), which can serve as a moving habitat, but can also cause major beaching events and environmental problems. Knowledge of its origins is important to help implement mitigation strategies and understand possible ecological impacts along its drifting pathways. Using high-resolution remote sensing images and numerical experiments, we track floating S. horneri in space and time between 2015 and 2023. Two possible origins are identified, one being far away from the ECS and the other being local, both of which are known to have benthic S. horneri. The study also reveals how S. horneri are transported from their source regions resulting in large-scale distributions previously observed in medium-resolution satellite imagery.

Pelagic Sargassum cleanup cost in Mexico

Pelagic Sargassum spp. (Sargassum) blooms in the tropical Atlantic began in 2011. Since then, frequent and significant beaching events have caused ecological, economic, and human-health-related problems in over 30 countries. On the Mexican Caribbean coast, massive beaching events began in late 2014 and, since 2018, have occurred annually, with high-volume landings lasting from five to seven months. This study analyzes data on Sargassum cleanup costs done by three municipalities (Puerto Morelos, Solidaridad, and Tulum) and five hotels between Tulum and Cancun. The annual harvested volumes ranged from 10,105–40,932 m3 per kilometer, resulting in US$ 0.3–1.1 M cleanup costs per kilometer. The prices of cleaning one cubic meter of Sargassum ranged from US$: 19–85. The expenses were influenced by cleanup management strategies rather than beach cast volumes. Hotels were more cost-effective than municipalities. For the city of Puerto Morelos, we additionally calculated the yearly and monthly cleanup costs using the mean per-unit price obtained from hotels within this municipality (US$ 27 per m3) and the Sargassum volumes removed monthly from the beach by 14 hotels during 2018, 2019, 2021, and 2022. The costs per kilometer for this municipality ranged from 0.8 to 1.5 M in years (Mean: 1.0 M) and US$ 10,186–100,446 over months, with mean values greater than US$ 70,000 from May to August. The data provided here can help governments and hotels to anticipate cleanup costs for forecasting purposes and industries interested in valorizing Sargassum.

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.

Monitoring Green Tide in the Yellow Sea Using High-Resolution Imagery and Deep Learning

Green tide beaching events have occurred frequently in the Yellow Sea since 2007, causing a series of ecological and economic problems. Satellite imagery has been widely applied to monitor green tide outbreaks in open water. Traditional satellite sensors, however, are limited by coarse resolution or a low revisit rate, making it difficult to provide timely distribution of information about green tides in the nearshore. In this study, both PlanetScope Super Dove images and unmanned aerial vehicle (UAV) images are used to monitor green tide beaching events on the southern side of Shandong Peninsula, China. A deep learning model (VGGUnet) is used to extract the green tide features and quantify the green tide coverage area or biomass density. Compared with the U-net model, the VGGUnet model has a higher accuracy on the Super Dove and UAV images, with F1-scores of 0.93 and 0.92, respectively. The VGGUnet model is then applied to monitor the distribution of green tide on the beach and in the nearshore water; the results suggest that the VGGUnet model can accurately extract green tide features while discarding other confusing features. By using the Super Dove and UAV images, green tide beaching events can be accurately monitored and are consistent with field investigations. From the perspective of near real-time green tide monitoring, high-resolution imagery combined with deep learning is an effective approach. The findings pave the way for monitoring and tracking green tides in coastal zones, as well as assisting in the prevention and control of green tide disasters.

Detection of Sargassum from Sentinel Satellite Sensors Using Deep Learning Approach

Since 2011, the proliferation of brown macro-algae of the genus Sargassum has considerably increased in the North Tropical Atlantic Sea, all the way from the Gulf of Guinea to the Caribbean Sea and the Gulf of Mexico. The large amount of Sargassum aggregations in that area cause major beaching events, which have a significant impact on the local economy and the environment and are starting to present a real threat to public health. In such a context, it is crucial to collect spatial and temporal data of Sargassum aggregations to understand their dynamics and predict stranding. Lately, indexes based on satellite imagery such as the Maximum Chlorophyll Index (MCI) or the Alternative Floating Algae Index (AFAI), have been developed and used to detect these Sargassum aggregations. However, their accuracy is questionable as they tend to detect various non-Sargassum features. To overcome false positive detection biases encountered by the index-thresholding methods, we developed two new deep learning models specific for Sargassum detection based on an encoder–decoder convolutional neural network (CNN). One was tuned to spectral bands from the multispectral instrument (MSI) onboard Sentinel-2 satellites and the other to the Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3 satellites. This specific new approach outperformed previous generalist deep learning models, such as ErisNet, UNet, and SegNet, in the detection of Sargassum from satellite images with the same training, with an F1-score of 0.88 using MSI images, and 0.76 using OLCI images. Indeed, the proposed CNN considered neighbor pixels, unlike ErisNet, and had fewer reduction levels than UNet and SegNet, allowing filiform objects such as Sargassum aggregations to be detected. Using both spectral and spatial features, it also yielded a better detection performance compared to algal index-based techniques. The CNN method proposed here recognizes new small aggregations that were previously undetected, provides more complete structures, and has a lower false-positive detection rate.

Spatio-temporal variability in drifting Fish Aggregating Device (dFAD) beaching events in the Seychelles Archipelago

AbstractPurse-seine fisheries use drifting Fish Aggregating Devices (dFADs), human-made floating objects, to facilitate the capture of tropical tunas. Currently, the majority of dFADs are constructed primarily of highly durable non-biodegradable materials and there is no legal obligation to recover dFADs after deployment, leading to beaching events and potentially negative environmental impacts. We assessed beachings as a function of intra- and inter-annual trends, water depth, distance from land, seasonality, and benthic habitat within the local context of the Seychelles Archipelago using trajectories of dFADs deployed by French purse seiners over 2008–2020. Overall, 3842 beaching events associated with 2371 distinct dFAD tracking buoys were identified. Beachings occurred most frequently during the winter monsoon (December–March). Due to the shallow Mahé Plateau, beachings occurred in both nearshore (≤ 5 km from land) and offshore (> 5 km) regions, predominantly in estimated depths less than 60 m. Despite representing < 20% of overall mapped habitat, the benthic habitat “Coral/Algae” had the highest beaching rate (35.3% of beachings), and therefore, beachings pose a significant concern for conservation. Our results provide a detailed view of the spatio-temporal pattern of beachings in the Seychelles, supporting the development of mitigation and prevention methods to reduce marine debris and perturbations to the marine environment.

Driving the blue fleet: Temporal variability and drivers behind bluebottle (Physalia physalis) beachings off Sydney, Australia.

Physalia physalis, the bluebottle in Australia, are colonial siphonophores that live at the surface of the ocean, mainly in tropical and subtropical waters. P. physalis are sometimes present in large swarms, and with tentacles capable of intense stings, they can negatively impact public health and commercial fisheries. P. physalis, which does not swim, is advected by ocean currents and winds acting on its gas-filled sail. While previous studies have attempted to model the drift of P. physalis, little is known about its sources, distribution, and the timing of its arrival to shore. In this study, we present a dataset with four years of daily P. physalis beachings and stings reports at three locations off Sydney's coast in Australia. We investigate the spatial and temporal variability of P. physalis presence (beachings and stings) in relation to different environmental parameters. This dataset shows a clear seasonal pattern where more P. physalis beachings occur in the Austral summer and less in winter. Cold ocean temperatures do not hinder the presence of P. physalis and the temperature seasonal cycle and that observed in P. physalis presence/absence time-series are out of phase by 3-4 months. We identify wind direction as the major driver of the temporal variability of P. physalis arrival to the shore, both at daily and seasonal time-scales. The differences observed between sites of the occurrence of beaching events is consistent with the geomorphology of the coastline which influences the frequency and direction of favorable wind conditions. We also show that rip currents, a physical mechanism occurring at the scale of the beach, can be a predictor of beaching events. This study is a first step towards understanding the dynamics of P. physalis transport and ultimately being able to predict its arrival to the coast and mitigating the number of people who experience painful stings and require medical help.

Monitoring Sargassum Inundation on Beaches and Nearshore Waters Using PlanetScope/Dove Observations

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> beaching events have been reported in recent years around the Caribbean Sea and FL, USA, causing numerous environmental and economic problems. Satellite remote sensing has been widely used to monitor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> blooms in open waters, yet due to either coarse spatial resolution or low-revisit frequency, it is difficult to provide timely information on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> inundation from traditional satellite instruments. In this study, we demonstrate the capacity of 3-m resolution daily Dove imagery in monitoring <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> beaching events on Miami beach (FL, USA) and Cancun beach (Mexico). A U-net deep learning (DL) computer model is developed to extract <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> features from Dove imagery over beaches and nearshore waters. Application of the model to Dove image sequences between May and August 2019 shows two major inundation events on both Miami beach and Cancun beach, consistent with local reports. With the availability of 3-m resolution PlanetScope/Dove and PlanetScope/SuperDove data around the globe, the findings suggest that it is possible to monitor dynamic inundation events of not only <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sargassum</i> but also other macroalgae in many other regions.

Seasonal Predictions of Holopelagic Sargassum Across the Tropical Atlantic Accounting for Uncertainty in Drivers and Processes: The SARTRAC Ensemble Forecast System

The holopelagic macroalgae sargassum has proliferated across the tropical Atlantic since 2011, of consequence for coastal populations from West Africa to the Caribbean with limited early warning of major beaching events. As part of an interdisciplinary project, ‘Teleconnected SARgassum risks across the Atlantic: building capacity for TRansformational Adaptation in the Caribbean and West Africa’ (SARTRAC), an ensemble forecast system, SARTRAC-EFS, is providing seasonal predictions of sargassum drift. An eddy-resolving ocean model hindcast provides the winds and currents necessary to generate ensemble members. Ensemble forecasts are then obtained for different combinations of ‘windage’, the fractional influence of winds on sargassum mats, and in situ rates of growth, mortality, and sinking. Forecasts for north and south of Jamaica are evaluated with satellite-observed distributions, associated with beaching events in specific years of heavy inundation, 2015 and 2018-20. These seasonal forecasts are evaluated, on lead times of up to 180 days. Forecasts are subject to leading modes of tropical climate variability, in particular the Atlantic Meridional Mode (AMM). More accurate forecasts for a given year are obtained with ensemble members from hindcast years with a similar spring AMM-index. This is most clearly evident during negative AMM phases in spring of 2015 and 2018, when positive sea surface temperature anomalies and anomalously weak trade winds were established across the northern tropics. On this evidence, SARTRAC-EFS is potentially useful in providing early warning of high sargassum prevalence. Extended to sargassum drift off West Africa, extensive cloud cover limits availability of the satellite data needed for full application and evaluation of SARTRAC-EFS in this region, although experimental forecasts off the coast of Ghana are found highly sensitive to the windage that is associated with strong onshore winds during boreal summer. Alongside other forecast systems, SARTRAC-EFS is providing useful early warnings of sargassum inundation at seasonal timescale.

Spatial management can significantly reduce dFAD beachings in Indian and Atlantic Ocean tropical tuna purse seine fisheries

Debris from fisheries pose significant threats to coastal marine ecosystems worldwide. Tropical tuna purse seine fisheries contribute to this problem via the construction and deployment of thousands of human-made drifting fish aggregating devices (dFADs) annually, many of which end up beaching in coastal areas. Here, we analyzed approximately 40,000 dFAD trajectories in the Indian Ocean and 12,000 dFAD trajectories in the Atlantic Ocean deployed over the decade 2008–2017 to identify where and when beachings occur. We find that there is tremendous promise for reducing beaching events by prohibiting deployments in areas most likely to lead to a beaching. For example, our results indicate that 21% to 40% (depending on effort redistribution after closure) of beachings can be prevented if deployments are prohibited in areas in the south of 8°S latitude, the Somali zone in winter, and the western Maldives in summer for the Indian Ocean, and in an elongated strip of areas adjacent to the western African coast for the Atlantic Ocean. In both oceans, the riskiest areas for beaching are not coincident with areas of high dFAD deployment activity, suggesting that these closures could be implemented with relatively minimal impact to fisheries. Furthermore, the existence of clear hotspots for beaching likelihood and the high rates of putative recovery of dFAD buoys by small-scale fishers in some areas suggests that early warning systems and dFAD recovery programs may be effective in areas that cannot be protected via closures if appropriate incentives can be provided to local partners for participating in these programs.

Sargassum contamination and consequences for downstream uses: a review

Sargassum spp. are brown algae present in the tropical and subtropical waters of the world’s oceans. Benthic or pelagic, Sargassum spp. represent substantial amounts of biomass when drifted and massive beaching events also named “golden tides” are challenging for environmental and tourism managers. The Sargassum spp. biomass can be regarded as offering economic opportunities; however, micropollutant contamination counteracts this wealth. This review describes the contaminant uptake processes and the concentrations reached by various Sargassum species in regard to national and international norms for a variety of applications. Amongst the heavy metals, perhaps total arsenic content is the most salient: phytoaccumulation of arsenic is due to confusion in the phosphate transporter between arsenic and phosphate, thus leading Sargassum spp. to bioaccumulate arsenic actively. The levels reached could well give cause for concern across all potential applications, in particular for human and animal use. Similarly, there are concerns for the widespread applications or disposal of this biomass due to environmental impacts in the case of storage, landfill or composting. Organic micropollutants are too rarely studied to assert that there is global contamination. However, research studies focused on Sargassum spp. contamination confirmed environmental threats. But, without exhaustive analysis of routine algae contamination, the standard contamination level cannot be defined. Treating beach-cast or drifting Sargassum spp. as a waste is a Gordian knot, in that it involves investment, work and disposal surfaces, whilst not necessarily providing environmental and economic gains. However, Sargassum spp. are a raw material, a resource rich in a broad variety of constituents that could be processed for commercial applications or which could be used for production of energy. In this paper the authors review the diverse applications that can be considered and describe the relevant regulations and norms related to contaminants and effluents that need to be taken into account. However, if valorizing Sargassum spp. is currently valuable and promising, the quality of the raw material is a key starting point because fresh and sand-free algae are required: offshore gathering solutions need to be developed in order to limit Sargassum sp. contamination by pollutants from land so as to hinder algae decay.

Environmental versus operational drivers of drifting FAD beaching in the Western and Central Pacific Ocean

In an effort to increase purse seine fishing efficiency for tropical tunas, over 30,000 drifting Fish Aggregating Devices (dFADs) are deployed every year by fishers in the Western and Central Pacific Ocean (WCPO). The use of dFADs also impacts ecosystems, in particular through marine pollution and dFAD beaching. This paper presents the first estimate of dFAD beaching events in the WCPO (>1300 in 2016–2017) and their distribution. Lagrangian simulations of virtual dFADs, released subject to contrasting deployment distributions, help us determine the relative importance of operational versus environmental drivers of dFADs drifting to beaching areas. The highest levels of beaching, occurring on Papua New Guinea and Solomon Islands, are likely a result of the prevailing westward oceanic circulation and subsequent local processes driving dFADs towards land. Similarly, high beaching rates in Tuvalu appear to be due to the general circulation of the WCPO. In contrast, beaching in Kiribati Gilbert Islands appear to be more strongly related to dFAD deployment strategy. These findings indicate that reducing beaching events via changes in deployment locations may be difficult. As such, management approaches combining dFAD deployment limits, the use of biodegradable dFADs, recoveries at-sea close to sensitive areas and/or beached dFAD removal should be considered.

Morphology, lipid composition, and reproduction in growth anomalies of the reef-building coral Porites evermanni and Porites lobata

Growth anomalies (GAs) are protuberant masses found on many coral species; their presence may be linked to increased ocean temperatures and bleaching stress. In 2014 and 2015, Hawai‘i experienced back-to-back beaching events, after which an increased number of growth anomalies were noted on massive Porites colonies. GAs and normal tissues were sampled from 19 P. evermanni and P. lobata colonies in 2015 and from each of 15 separate P. evermanni colonies on six dates from June 2016 to August 2017, encompassing two annual reproductive cycles. Compared to normal tissue, GAs had significantly larger corallites in all dimensions in both P. evermanni and P. lobata. GAs of P. evermanni also had reduced amounts of lipid and lower functional lipid ratios across all time points. Across tissue types, lipid content was generally higher in winter (December) and spring (April) than in summer months (June/July), but was not correlated with reproductive condition. While GAs are generally non-reproductive in other corals, GA tissues in P. evermanni contained elevated numbers of oocytes in 2017. Compared to normal tissue, GAs in P. evermanni had aberrant corallite morphology and likely committed proportionally more energy to growth and less to energy storage.

First record of beaching events for a calycophoran siphonophore: Abylopsis tetragona (Otto, 1823) at the Strait of Gibraltar

Two beaching events of the calycophoran siphonophore Abylopsis tetragona (Otto, 1823) were observed in two different areas of the Strait of Gibraltar during the cold season. The first was discovered on November 2014, on Getares Beach (Algeciras Bay, Mediterranean part of the Strait of Gibraltar), where more than 700 colonies were found deposited along the tideline. The second event was discovered on January 2015, on Paloma Baja Beach (Tarifa, Atlantic part of the Strait of Gibraltar) where an average density of 170 colonies m−2 was spread along the seashore. Both events seemed to be promoted by strong easterly winds, preceded by upwelling episodes that may have concentrated high densities of the siphonophore in superficial layers. This study represents the first report of a calycophoran siphonophore mass stranding. The records were made thanks to citizen science and jellyfish outreach at secondary schools (PERSEUS@school initiative), illustrating the importance of citizen science projects in observing natural phenomena. We consider the monitoring and recording of cnidarian stranding events especially important in highly productive and biologically active areas such as the Strait of Gibraltar.

Simulating transport pathways of pelagic Sargassum from the Equatorial Atlantic into the Caribbean Sea

Since 2011, beach inundation of massive amounts of pelagic Sargassum algae has occurred around the Caribbean nations and islands. Previous studies have applied satellite ocean color to determine the origins of this phenomenon. These techniques, combined with complementary approaches, suggest that, rather than blooms originating in the Caribbean, they arrive from the Equatorial Atlantic. However, oceanographic context for these occurrences remains limited. Here, we present results from synthetic particle tracking experiments that characterize the interannual and seasonal dynamics of ocean currents and winds likely to influence the transport of Sargassum from the Equatorial Atlantic into the Caribbean Sea. Our findings suggest that Sargassum present in the western Equatorial Atlantic (west of longitude 50°W) has a high probability of entering the Caribbean Sea within a year’s time. Transport routes include the Guiana Current, North Brazil Current Rings, and the North Equatorial Current north of the North Brazil Current Retroflection. The amount of Sargassum following each route varies seasonally. This has important implications for the amount of time it takes Sargassum to reach the Caribbean Sea. By weighting particle transport predictions with Sargassum concentrations at release sites in the western Equatorial Atlantic, our simulations explain close to 90% of the annual variation in observed Sargassum abundance entering the Caribbean Sea. Additionally, results from our numerical experiments are in good agreement with observations of variability in the timing of Sargassum movement from the Equatorial Atlantic to the Caribbean, and observations of the spatial extent of Sargassum occurrence throughout the Caribbean. However, this work also highlights some areas of uncertainty that should be examined, in particular the effect of “windage” and other surface transport processes on the movement of Sargassum. Our results provide a useful launching point to predict Sargassum beaching events along the Caribbean islands well in advance of their occurrence and, more generally, to understand the movement ecology of a floating ecosystem that is essential habitat to numerous marine species.

The Occurrence of Paraffin and Other Petroleum Waxes in the Marine Environment: A Review of the Current Legislative Framework and Shipping Operational Practices

Among the various materials that make up marine debris, lumps of petroleum waxes such as paraffin and microcrystalline wax, are regularly found on beaches worldwide, although not included in the current definition of marine litter. Ingestion by marine organisms is occasionally documented in the scientific literature and mass beaching events are frequently reported along the European coasts, with obvious detrimental consequences to the local communities that have to manage the clean-up and disposal of this substance. According to Annex II of the MARPOL regulation, petroleum waxes are classified as “high viscosity, solidifying and persistent floating products”, whose discharge at sea of tank-washing residues is strictly regulated, but currently permitted within certain limits. Starting from the description of a large stranding event occurred along the Italian coasts in 2017, we review the existing knowledge and regulatory framework and urge the relevant authorities to address this issue, showing that wax pollution is creating evident damages to the European coastal municipalities. Pending further investigations on the potential hazard that this kind of pollution is posing to marine ecosystems, we suggest a careful and more stringent revision of the policies regulating discharges of these products at sea.

Predicting Sargassum blooms in the Caribbean Sea from MODIS observations

AbstractRecurrent and significant Sargassum beaching events in the Caribbean Sea (CS) have caused serious environmental and economic problems, calling for a long‐term prediction capacity of Sargassum blooms. Here we present predictions based on a hindcast of 2000–2016 observations from Moderate Resolution Imaging Spectroradiometer (MODIS), which showed Sargassum abundance in the CS and the Central West Atlantic (CWA), as well as connectivity between the two regions with time lags. This information was used to derive bloom and nonbloom probability matrices for each 1° square in the CS for the months of May–August, predicted from bloom conditions in a hotspot region in the CWA in February. A suite of standard statistical measures were used to gauge the prediction accuracy, among which the user's accuracy and kappa statistics showed high fidelity of the probability maps in predicting both blooms and nonblooms in the eastern CS with several months of lead time, with overall accuracy often exceeding 80%. The bloom probability maps from this hindcast analysis will provide early warnings to better study Sargassum blooms and prepare for beaching events near the study region. This approach may also be extendable to many other regions around the world that face similar challenges and opportunities of macroalgal blooms and beaching events.

&lt;em&gt;Sargassum&lt;/em&gt; Watch Warns of Incoming Seaweed

The Sargassum Watch System processes satellite data and feeds results to a Web portal, giving decision makers timely information on seaweed location and warnings for potential beaching events.

Green and golden seaweed tides on the rise

Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years. These 'seaweed tides' can harm tourism-based economies, smother aquaculture operations or disrupt traditional artisanal fisheries. Coastal eutrophication is the obvious, ultimate explanation for the increase in seaweed biomass, but the proximate processes that are responsible for individual beaching events are complex and require dedicated study to develop effective mitigation strategies. Harvesting the macroalgae, a valuable raw material, before they beach could well be developed into an effective solution.