Search Results (11)

Since 2011, Sargassum seaweed has spread widely outside the Sargasso Sea, causing massive strandings on the coasts of the West Indies and Mexico, causing serious economic, ecological, and health problems. This Atlantic pelagic alga has the characteristic of moving in rafts. According to in situ observations, their size and shape can vary with the wind. To better understand the effect of wind on Sargassum coverage and aggregation size, we conducted a large temporal (2019–2022) and spatial scale study in the West Indies using OLCI/Sentinel-3 satellite imagery. During this period, a database of nearly 1 million Sentinel-3 aggregations, including their geometric and wind characteristics, was established. Analysis of the size distribution showed that wind has a dual effect on disaggregation and agglomeration depending on wind speed and aggregation size: (1) low winds favor agglomeration for the smallest aggregations and disaggregation for the largest aggregations; (2) high winds favor disaggregation for all aggregation sizes. In addition, topography also plays a role in size distribution: the Caribbean arc favors agglomeration over offshore zones, and coastal areas favor disaggregation over offshore zones. Full article

Pelagic Sargassum landings (hereby referred to as sargasso) increased dramatically in 2011 throughout the equatorial tropical Atlantic due to the formation of the Great Atlantic Sargassum Belt (GASB). Despite increasing reports, understanding of local abundances and vegetative characteristics, especially in South Florida, remains limited. From 2018 to 2021, sargasso was collected at two South Florida beaches, with additional sampling at a third beach to assess nutrient and heavy metal concentrations. Biomass landings varied greatly, with S. fluitans III predominant during the “peak season” (May to July) and S. natans I predominant in the “off season”, while S. natans VIII was consistently least abundant. This suggests that South Florida may receive sargasso from the Sargasso Sea during the low season and from the GASB during the peak sargasso season. Across all three morphotypes, mean nitrogen (N) and phosphorus (P) contents were 0.97% and 0.04% (dry weight), respectively. Out of the 16 heavy metals detected, our values were similar to those reported across the Caribbean. Arsenic was the most prevalent heavy metal, with sargasso containing epibionts having higher arsenic concentrations. These results provide comprehensive information to better understand the characteristics and potential origin of sargasso landings in South Florida. Full article

Since 2011, the distribution, abundance, and composition of holopelagic Sargassum spp. (sargasso) have changed by the emergence of the Great Atlantic Sargasso Belt (GASB) in the northern tropical Atlantic. We expected that the north of the Cuban coast would receive sargasso from both the original Sargasso Sea and the GASB. We systematically monitored six beaches on the NW coast of Cuba to assess changes in sargasso composition from June 2019 to June 2021. During landing months, mean Sargasso wet biomass was at 1.54 kg/m² (SE: 0.7), which was considerably lower than the sargasso on the Atlantic coasts directly impacted by GASB. Eleven out of 13 landings occurred in the autumn-winter seasons 2019–2020 and 2020–2021, with a dominance of S. natans I (accounting for 41–63% of total biomass), followed by S. fluitans III (25–36%) and S. natans VIII (12–31%). This composition is similar to those observed on the Sargasso Sea. During this season, dominant winds (≥14 km/h) came from northern (N), eastern (E), and east-northeastern (ENE) directions. In May and August 2020 (spring-summer season), S. fluitans III dominated (52–56%), followed by S. natans VIII (33–43%) and S. natans I (5–12%). This composition is similar to those observed on GASB-impacted Atlantic coasts in the spring-summer seasons (April to September). During this season, dominant winds (≥20 km/h) came from eastern (E) and east-northeastern (ENE) directions. Thus, the NW Cuba’s morphotype composition suggests that landings have different origin sources depending on season and specific meteorological and oceanographic conditions. Full article

The intensity of climate change impacts on coastal ecosystems is determined by a combination of global, regional, and local drivers. However, many studies on the impact of climate change on ecosystems only consider trends associated with global changes. To assess the global, regional, and local trends, this research analyzes different climates in the coastal zone of the Mexican Caribbean. These drivers include sea level rise in synergy with tectonic activity, sea surface temperature, atmospheric pressure, precipitation, waves and winds. Marine climate variability from 1980 to 2020 was assessed from historical records by local/governmental agencies and the European Centre for Medium-Range Weather Forecasting. An up-to-date diagnosis of local changes of the coastal ecosystems was made, the magnitudes of change differ from the global means, which must be considered when identifying local climate change impacts. Coastal ecosystems, such as mangroves, coastal dunes, sandy beaches and seagrass meadows, showed no changes consistent with geophysical drivers associated with climate change. The exception was coral reefs, where increasing SST is related to coral bleaching. Regional and local anthropic drivers or disturbances other than those related to climate change, including eutrophication, massive influxes of the brown algae Sargasso and changes in land use, induced degradation of the coastal ecosystems. Communities often do not have the capacity to cope with global climate change, but the main impacts on coastal ecosystems in the coastal zone studied were induced by regional and local drivers/disturbances that can be better managed using monitoring programmes and specific management strategies. Climate change induces pressures on coastal ecosystems that affect their functioning, physiology and species distribution; therefore, this study highlights the need to understand how climate-change-related phenomena will affect ecosystems and which geophysical drivers may have priority effects. It also highlights the importance of developing robust regional/local databases to enable stakeholders to diagnose the state of coastal ecosystems and to monitor the effectiveness of actions to prevent or reverse undesirable changes. Full article

Due to climate change and its associated factors, there has been an increased influx of pelagic brown algae biomass drifting freely in the Caribbean Sea in recent years. Its use as an industrial recyclable material is feasible, although pelagic Sargassum species have Arsenic (As) heavy metal content; among 531 tested pesticide residues applied to vegetables, fruit, infant food, herbs, and spices, zero were found in Sargassum. Sargassum also contains sulfated polysaccharides and oligosaccharides, which are known to be beneficial immunomodulators. Our results thus suggest Sargassum to be a functionally useful organic material in small quantities as an additive in animal feed. With improved chemical extraction methods, it could also be highly effective in adjusted proportions in cosmetics and for other industrial uses. A viable solution for predicting and tracking the large-scale movements of algal masses is provided. Furthermore, a method for addressing increasing Sargassum influx is proposed via its use as an industrial recyclable material following composition analysis, evaluation and safety assessments for cosmetic use, and research and design of new beauty products and other functional cosmetics. Full article

Eels use the swimbladder for buoyancy control. The ductus pneumaticus connecting the esophagus with the swimbladder is closed soon after initial opening of the swimbladder in the glass eel stage, so that eels are functionally physoclist. Subsequent filling of the swimbladder is achieved by activity of gas gland cells in the swimbladder epithelium and countercurrent concentration in the rete mirabile. Gas gland cells produce and release lactic acid and CO₂. In blood, acidification induces a release of oxygen from the hemoglobin (Root effect). The resulting increases in PO₂ and PCO₂ provide diffusion gradients for the diffusion of oxygen and CO₂ into the swimbladder, the main gases secreted into the swimbladder. In addition, the partial pressure of these two gases remains elevated in venous blood leaving the swimbladder epithelium and returning to the rete mirabile. Back-diffusion from venous to arterial capillaries in the rete results in countercurrent concentration, allowing for the generation of high gas partial pressures, required for filling the swimbladder under elevated hydrostatic pressure. The transition of the yellow eel to the silver eel stage (silvering) is accompanied by a significant improvement in swimbladder function, but swimbladder volume cannot be kept constant during the daily vertical migrations silver eels perform during their spawning migration back to the spawning grounds in the Sargasso Sea. Infection of the swimbladder with the nematode Anguillicola crassus significantly impairs the function of the swimbladder as a buoyancy organ. Full article

Nutrient pollution remains one of the greatest threats to water quality and imposes numerous public health and ecological concerns. Phosphate, the most common form of phosphorus, is one of the key nutrients necessary for plant growth. However, phosphate concentration in water should be carefully monitored for environmental protection requirements. Hence, an easy-to-use, field-deployable, and reliable device is needed to measure phosphate concentrations in the field. In this study, an inexpensive dip strip is developed for the detection of low concentrations of phosphate in water and seawater. In this device, ascorbic acid/antimony reagent was dried on blotting paper, which served as the detection zone, and was followed by a wet chemistry protocol using the molybdenum method. Ammonium molybdate and sulfuric acid were separately stored in liquid form to significantly improve the lifetime of the device and enhance the reproducibility of its performance. The device was tested with deionized water and Sargasso Sea seawater. The limits of detection and quantification for the optimized device using a desktop scanner were 0.134 ppm and 0.472 ppm for phosphate in water and 0.438 ppm and 1.961 ppm in seawater, respectively. The use of the portable infrared lightbox previously developed at our lab improved the limits of detection and quantification by a factor of three and were 0.156 ppm and 0.769 ppm for the Sargasso Sea seawater. The device’s shelf life, storage conditions, and limit of detection are superior to what was previously reported for the paper-based phosphate detection devices. Full article

Since late 2014, the Mexican Caribbean coast has periodically received massive, atypical influxes of pelagic Sargassum spp. (sargasso). Negative impacts associated with these influxes include mortality of nearshore benthic flora and fauna, beach erosion, pollution, decreasing tourism and high management costs. To understand the dynamics of the sargasso influx, we used Landsat 8 imagery (from 2016 to mid-2020) to record the coverage of sargasso in the sea off the Mexican Caribbean coastline, with a maximum reported in September 2018. Satellite image analysis also showed local differences in the quantity of beached sargasso along the coastline. Over the years, good practice for collection on the beach and for off-shore collection of sargasso have been established through trial and error, and the Mexican Government and hotel industry have spent millions of dollars on removal and off-shore detention of sargasso. Notwithstanding, sargasso also has various properties that could be harnessed in local industries. The stimulation of local industrial growth would offer alternatives to the dependence on tourism, as a circular economy, based on sargasso, is developed. Full article

The steep US Virgin Islands Shelf Break (VISB) and the Virgin Islands Trough (VIT) at the Northeastern Caribbean Sea comprise a dynamic region of the Atlantic Ocean. In situ oceanographic data collected in the region during April 2017 were used to examine the spatial variability in temperature, density, salinity, and relative Chlorophyll-a. Analysis of data from the upper 300 m of the water column, that include deep and shallow water stations in the shelf break region, shows strong stratification of the water column. Stations shallower than 800 m along the shelf break are more variable in temperature, density, and salinity than those that are deeper than 800 m along the trough. For shallow stations, the mixed layer depth deepens along-shelf from West to East while at the deep stations the opposite occurs. Salinity maxima exhibit more variability in depth and range of values in the shallow stations compared to deep stations. Six different types of water masses that contribute to the strong stratification in the region were identified in our study: Caribbean Surface Water, Subtropical Underwater, Sargasso Sea Water, Tropical Atlantic Central Water, Antarctic Intermediate Water, and North Atlantic Deep Water. The upper level Caribbean Surface Water, Subtropical Underwater, and Sargasso Sea Water are present in shallow stations, indicating potential meridional intrusions from the VIT to the VISB which may not be resolved by current ocean circulation models and are not captured in satellite data. The analysis presented here indicates that competing physical processes may be controlling the vertical structure of the water column in the region and merit further examination. Full article

The following article discusses Gabriel García Márquez’s Of Love and Other Demons and Jean Rhys’s Wide Sargasso Sea. Specifically, this article will discuss the parallel ways that two novels critique the nature of postcolonial development in the Caribbean, particularly in regard to race and hybridity. Within the novels, the child protagonists and their African/black creole nursemaids follow surprisingly similar plots, though the settings, contexts, and styles of the two texts differ greatly. In these two novels while the white protagonists both die because of their hybrid navigation of their environment, their nurse/mothers survive, largely because of their maintenance of African practices. In many ways, the nurse mothers’ survival and attempts to heal their charges present potential antidotes for the “disease” produced by slavery. The purpose of this paper is to explore those parallel developments in plot, and to look at the ways the two texts disrupt and reinforce colonial hegemonic norms through their depictions of both the nurses and their charges. Full article

The primary measure of the quality of sea surface temperature (SST) fields obtained from satellite-borne infrared sensors has been the bias and variance of matchups with co-located in-situ values. Because such matchups tend to be widely separated, these bias and variance estimates are not necessarily a good measure of small scale (several pixels) gradients in these fields because one of the primary contributors to the uncertainty in satellite retrievals is atmospheric contamination, which tends to have large spatial scales compared with the pixel separation of infrared sensors. Hence, there is not a good measure to use in selecting SST fields appropriate for the study of submesoscale processes and, in particular, of processes associated with near-surface fronts, both of which have recently seen a rapid increase in interest. In this study, two methods are examined to address this problem, one based on spectra of the SST data and the other on their variograms. To evaluate the methods, instrument noise was estimated in Level-2 Visible-Infrared Imager-Radiometer Suite (VIIRS) and Advanced Very High Resolution Radiometer (AVHRR) SST fields of the Sargasso Sea. The two methods provided very nearly identical results for AVHRR: along-scan values of approximately 0.18 K for both day and night and along-track values of 0.21 K for day and night. By contrast, the instrument noise estimated for VIIRS varied by method, scan geometry and day-night. Specifically, daytime, along-scan (along-track), spectral estimates were found to be approximately 0.05 K (0.08 K) and the corresponding nighttime values of 0.02 K (0.03 K). Daytime estimates based on the variogram were found to be 0.08 K (0.10 K) with the corresponding nighttime values of 0.04 K (0.06 K). Taken together, AVHRR instrument noise is significantly larger than VIIRS instrument noise, along-track noise is larger than along-scan noise and daytime levels are higher than nighttime levels. Given the similarity of results and the less stringent preprocessing requirements, the variogram is the preferred method, although there is a suggestion that this approach overestimates the noise for high quality data in dynamically quiet regions. Finally, simulations of the impact of noise on the determination of SST gradients show that on average the gradient magnitude for typical ocean gradients will be accurately estimated with VIIRS but substantially overestimated with AVHRR. Full article