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Impacts of the Caribbean Sargassum Influx on Sea Turtle Nesting Ecology
... In this study, we built on previous work (Maurer et al., 2019) to quantify how Sargassum alters the thermal conditions of sea turtle nests. Our working hypothesis was that Sargassum cools below-ground temperatures due to a shading effect, but it is also possible that it could have an insulating or negligible effect on belowground temperatures. ...
... When translating these differences to hypothetical effects on sea turtle embryos, we note that the magnitudes of treatment effects are associated with experimentally designated amounts of Sargassum. Based on our field observations throughout Antigua (Long Island and beaches in southern and northeastern mainland Antigua) these amounts are realistic and relevant, but abundance will vary at different nesting beaches and on different sections within a beach (Maurer et al., 2019). Nonetheless, the differences in temperature that we documented offer an opportunity to explore implications for the developmental outcomes of sea turtle embryos. ...
Global environmental change has featured a rise in macroalgae blooms. These events generate immense amounts of biomass that can subsequently arrive on shorelines. Such a scenario has been playing out since 2011 in the tropical and subtropical Atlantic, where Sargassum spp. have been causing periodic ‘golden tides’ in coastal habitats. Here we describe impacts on sea turtle nesting ecology, with a focus on the below-ground thermal environment for incubating eggs. Sargassum may blanket the surface of beaches due to natural wave or wind energy and can be redistributed via anthropogenic beach cleaning. When it covers egg clutches, it may alter incubation temperatures and therefore affect both embryonic survival and primary sex ratios. To evaluate the thermal impacts of Sargassum, we measured sand temperatures with data loggers buried under Sargassum cover treatments on a beach in Antigua, West Indies. Our split-plot experiment also tested for effects from shade, season (summer versus autumn), and high rainfall events. We modeled temperatures with a mixed-effects model and, surprisingly, our most compelling finding suggested that Sargassum's effects on below-ground temperatures were contingent on season. Greater Sargassum cover was associated with a cooling effect in the summer but warming in the autumn. We assume that the model term for season integrates several climate-related factors that vary seasonally in the Eastern Caribbean and modulate Sargassum's impact, including windspeeds. Comparing estimated marginal means for the high-cover treatments versus the controls, Sargassum cover led to a 0.21 °C increase in the autumn and a 0.17 °C decrease in the summer; these thermal changes can significantly impact developmental outcomes for sea turtle embryos. Atlantic nesting beach managers should monitor this macroalgal phenomenon and can use these data to begin to infer impacts on sea turtle populations and develop potential management strategies.
... Indeed, sea turtles in the North Atlantic exhibit an early pelagic stage during which many individuals may associate with floating seaweed [ 26-28 , 33 ]. By contrast, most studies documenting impacts of Sargassum inundation on coasts suggest negative impacts on nearshore foraging habitats and nesting beaches -accumulation of the macroalgae may alter littoral waters [8] and create a physical barrier to nesting adults and hatchlings [34,35,36,37, although see 38]. Biomass accumulation could therefore have consequences for population dynamics through effects on reproduction, space use, energetics, and neonate recruitment [ 34 , 37 ]. ...
... We do not investigate impacts on other key life stages present at nesting beaches, namely eggs and hatchlings. Macroalgal biomass may impede hatchlings as they attempt to exit nest chambers and access ocean habitats and may cause changes to egg incubation environments when it collects atop nests [34][35][36][37] . Possible effects on egg thermal conditions are noteworthy given that incubation temperatures affect embryo survival, morphological development, and sex ratios [56] . ...
One characteristic of global change is an increase in the frequency and magnitude of algae blooms. Although a large body of work has documented severe ecological impacts, such as mortality due to toxins or hypoxia, less research has described sublethal effects that may still affect population dynamics. Here, we focus on blooming Sargassum macroalgae in the North Atlantic and describe effects on nesting sea turtles. Since 2011, large masses of the algae have been inundating Atlantic nesting habitats. We documented the accumulation of Sargassum at Long Island, Antigua, and quantified effects on a rookery of hawksbill sea turtles (Eretmochelys imbricata). Using monitoring data from 2010–2019, we analyzed population- and individual-level patterns in nesting. Our results suggest that sea turtles respond to Sargassum at nesting beaches by shifting space use away from heavily impacted areas. We also tested for an effect on nesting success, but found no change in the years and areas most impacted by Sargassum. The algae may not increase the energetic costs of nesting after a turtle has emerged onto the beach, but we speculate that costs are imposed in algae-filled waters as turtles initially seek to emerge. As the Sargassum “invasion” continues, sea turtles at impacted sites will need to exhibit plasticity when choosing nesting sites, and nest densities may increase in areas with less Sargassum present. Individuals may also be required to expend more energy per nesting season. More broadly, this work demonstrates that algae blooms can have sublethal effects on fauna that affect population dynamics.
... Macroalgae blooms of the genera Ulva and Sargassum pelagic (Sargassum fluitans and Sargassum Natans) generate immense amounts of floating tidal green and gold algae, which are carried by currents and winds inundating coastlines and affecting a multitude of species. Floating rows of algae seasonally affect the Caribbean forming a "transatlantic sargassum belt" stretching from the Gulf of Mexico to West Africa Putman and. the abundance of sargassum on beaches today has increased 200-fold when compared to 2015Maurer et al., 2019 Sargassum stranded on beaches by natural wave carry, wind energy, and redistribution through cleaning can alter subterranean thermal sand environments for nesting and incubation of sea turtle eggs with changes in embryonic survival, Johns et al., 2020. Previous studies of turtle reproductive environments that consider variables attached to the reality of reproduction and with effects on sargassum coverage determined that a large amount of macroalgae represents a blockage for females that try to access the sandy nesting substrate Maurer et al., 2015;Ricardo and Martín, 2015, as well as for the hatchlings that seek the sea after leaving the Gavio and Santos-Martínez nests, 2018. ...
The invasive presence of pelagic sargassum on the coasts has increased disproportionately in the last decade, causing great damage to the ecosystems of coastal and marine flora, and fauna, as well as the tourism sector, due to the fact that the sargassum when it enters into decomposition generates fetid odors, detachments of Ammonium concentrations and Hydrogen Sulfide H2S that together with hypoxic conditions were the mass death cause of species, therefore it is necessary to clean affected areas. The aim of this research was to analyze how to reduce erosion in beach dunes, through the technological implementation for the treatment of the mixture sand - dead pelagic sargassum. The methodology had a mixed approach to propose the application of centrifugation and precipitation technologies to significantly reduce beach dunes erosion. However, the machines that do not have this process present a sand-sargassum mixture as residue that, when removed, erodes the dunes. The results obtained were the proposal for the implementation of a new complementary process to those carried out by beach cleaning machines to reduce erosion, in addition to compacting the sargassum for its transfer optimization.
... Las masas de Sargassum spp. en tierra y cerca de la costa interfieren también el viaje de las tortugas juveniles, afectando su anidación causada por las actividades de recolección y limpieza mecánica en la playa, con su consecuente compactación (Maurer et al., 2015(Maurer et al., , 2018. Durante el 2015 en la península de Guanahacabibes (S de Cuba), se registró una llegada de sargazo de 1,5 m de potencia que afectó, en un 50 %, el éxito de anidación de las tortugas (Azanza-Ricardo & Pérez-Martín, 2016). ...
Article La retirada de restos vegetales de Sargassum spp. depositados sobre la playa emergida constituyen una parte de la limpieza de playas en el Caribe. Estas gestiones realizadas a lo largo de las últimas décadas han dado lugar a la pérdida de superficies y volúmenes de playa y dunas. El estudio analiza los volúmenes de sedimento retirados mediante la limpieza de Sargassum spp. en 12 playas de México y República Dominicana, cuantificando el volumen total en 18.987,3 m 3 , con un 61,23 % de sedimento intercalado, equivalente a 9.872,36 T de arena. Este tipo de ges-tión supone un impacto geomorfológico continuo con una importante pérdida de sedimento anual que afecta a la estabilidad del balance sedimentario del sistema playa. Palabras clave: Caribe, Sargassum spp., limpieza de playas, erosión. Loss of sediment associated with the removal of deposits of Sargassum spp. on the beaches of the Caribbean Part of the cleaning of beaches in the Caribbean islands involves the removal of Sargassum spp. that remains deposited on the emerged beach and dunes. The study analyses the volumes of sediment removed with the Sar-gassum spp. at 12 beaches in México and the Dominican Republic, quantifying the volume of material removed at 18,987.3 m 3 , of which an estimated 61.23 % (or 9,872.36 T) was sand. This kind of management involves a continuous geomorphological impact with an important loss of sediment that affects the stability of the sedimentary balance of the beach system. El turismo de sol y playa es la modalidad que mayores flujos genera a escala internacional y supone una importante aportación al producto interior bruto (PIB) en países denominados turísticos. En el Caribe, México y República Dominicana son unos de los principales destinos turísticos de este tipo con una aportación al PIB de 8,7 y 8,4 % respectivamente, y modelos turísticos basados en el producto turístico litoral. Para mantener una playa a largo plazo, el balance debe ser positivo, o al menos equilibrado, ya que los balances negativos en última instancia causan su erosión (Komar, 1999). La presión derivada de la industria turística ha hecho que muchos ambientes sedimentarios litorales se hayan visto gravemente afectados a lo largo de la costa. Los ambientes litorales de México y República Dominicana (Fig. 1) están some-tidos desde hace décadas a una problemática geoam-biental asociada a su uso y explotación (Peynador & Méndez-Sánchez, 2010; Roig-Munar et al., 2018; Guima-rais et al., 2021), pero en la última década presentan la llegada y varado masivo de sargazo, la gestión de su retirada generando impactos geoambientales con pérdida de superficie y volumen de playa. Una de las preocupaciones fundamentales nace inicialmente desde el sector turístico en la región del Caribe por la afectación que implican las grandes masas de sargazo Pérdida de sedimento asociada a la retirada de depósitos de Sargassum spp. en las playas del Caribe
... The impacts include aesthetics (of the previously pristine white beaches), additional organic matter input, light attenuation, anoxia, and leaching ( van Tussenbroek et al., 2017;Chavez et al., 2020). The consequences are mortality of near-shore benthos, including seagrass and coral (Silva et al., 2016), beach erosion (van Tussenbroek et al., 2017;Silva et al., 2020), the modification of sediment structure (Maurer, 2019), changes in the trophic relationships (Cabanillas-Terań et al., 2019), respiratory and skin health issues in humans (Resiere et al., 2018), and economic losses for the tourist industry. Although the latter has not been fully assessed, losses are estimated to be substantial as the beaches lost their attractiveness due to the unsightly accumulations of sargasso (Langin, 2018). ...
As the biomass of pelagic Sargassum spp. increased across the North Atlantic equatorial recirculation region from 2011 onwards, massive rafts of sargasso appeared in the Western Caribbean in 2015, 2018, 2019, and 2020. These events raised concerns regarding their negative consequences on the environment, local income, and human wellbeing. As adequate monitoring and analysis tools are needed for designing in-water and on-beach control strategies to reduce potential negative impacts, more robust and spatially explicit information is needed in order to improve sargasso management and focus restoration efforts. In this paper, we offer a spatiotemporal multiscale description of sargasso distribution and dynamics for 2014–2020 in the Mexican Caribbean: (1) for the entire region (millions of km2); (2) at the local scale (thousands of km2) evaluating the dynamics inside the reef lagoon at Puerto Morelos, Mexico; and finally, (3) specific beach observations (hundreds of km2) derived from data on beach cleaning volumes. Fifteen areas in the Mexican Caribbean, with different sargasso dispersions and on-shore accumulations, were evaluated. The areas around Tulum, Solidaridad, and Puerto Morelos have the most extreme and most frequent episodes but also exhibited the greatest seasonal variability. Extreme sargasso presence can occur in the Western Caribbean in any season, albeit with increasing coverage and recurrence in the summer. Images from a coastal video monitoring station at Puerto Morelos showed that massive sargasso beaching was associated with low energy conditions (Hs< 0.25 m, wind speed<4 m/s, neap tide), while non-accumulation of sargasso on the beach occurred under high energy conditions (Hs >0.4 m, wind speed = 8 m/s, spring tide). Time-series analyses of sargasso beaching showed different periods of historic maximum sargasso coverage over July–October 2018 and others in January–February 2019. Wind and wave regimes influenced sargasso in distinct ways, depending on the coastal section, probably related to coastline morphology, oceanic regime, or the extent of the continental platform. This work presents the longest systematic time series (2014-2020) of high resolution satellite detected sargasso in Mexico. Spatial and temporal patterns are proposed as fundamental steps for managing sargasso accumulations.
... For instance, seagrass and coral mortality has been observed to increase due to decreasing light, PH, and oxygen levels in nearshore waters, associated with the decaying sargassum masses on the beach (Van Tussenbroek et al., 2017). Also, fish and crustacean mortality have been related to increased ammonium and hydrogen sulfide concentrations and hypoxia in reef lagoons (Rodríguez-Martínez et al., 2019), and nesting of turtles has been hindered due to the sargassum masses on the beach and in shallow water (Maurer et al., 2015(Maurer et al., , 2019. Besides, local economies suffered with a reduced income as a result of a lower number of beach visitors during the sargassum season and costs associated with artificial sargassum removal (Chávez et al., 2020). ...
Massive quantities of the pelagic brown macroalgae Sargassum spp. (sargassum) have been invading the Caribbean and West African shores since 2011, causing devastating effects on the coastal ecosystem and local economy. Little is known about sargassum beaching dynamics and the capacity of the coastal system to naturally remove beached sargassum. Here, we characterize the temporal variation in arriving and beached sargassum in a reef lagoon using a 5.2‐year data set of hourly optical imagery, and identify the governing hydrometeorological conditions. Image classification reveals interannual variability in the start, duration, and intensity of the sargassum arrival season. Arrivals are associated with relatively low energy onshore directed winds and waves, and offshore abundance of sargassum. Furthermore, nearshore sargassum mat size is found to decrease with decreasing wave/wind energy. Once sargassum beaches, a berm of wrack is formed. Natural wrack removal was observed under elevated water levels and increased wave action. Three types of wrack removal were distinguished, depending on the water level η with respect to the berm crest height zc and berm crest toe zt: gradual berm destruction with gaps developing in the seaward berm edge that grow larger with time (Type I; zt<η<zc) and abrupt berm destruction with part of the wrack depositing on the upper beach (Type II; η>zc) or in the dunes (Type III; η≫zc). Higher energy waves activate the reef circulation, which is suspected to flush part of the wrack out of the reef lagoon. We propose a conceptual model of nearshore sargassum dynamics in a reef lagoon system.
... Efforts to prevent the sargasso reaching the coast, or to remove it from the beach before the masses decompose, have often been insufficient, or absent. Thus, the accumulation of sargasso on the coast and inadequate clean-up activities have resulted in beach erosion, sand compaction and interfered with marine turtle nesting and hatching [15]. Inland, inadequate disposal of sargasso threatens the aquifer, the only source of freshwater locally, contaminating it with nutrients, salt, metals and other contaminants (see Figure S1). ...
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 offshore 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 offshore 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.
... Leachates and particulate organic matter from stranded decaying algal masses depleted the oxygen in near shore waters and reduced visibility of the water column, causing mortality of near-shore seagrasses and fauna (van Tussenbroek et al., 2017;Rodríguez-Martínez et al., 2019). Onshore and near shore masses of sargasso interfered with the seaward journeys of the juvenile turtles (Maurer, De Neef & Stapleton, 2015), affected sea turtle nestings (Maurer, Stapleton & Layman, 2018) and altered the trophic structure of the sea urchin Diadema antillarum in coastal marine systems (Cabanillas-Terán et al., 2019). Massive beachings also enhanced beach erosion (van Tussenbroek et al., 2017). ...
The massive influx of pelagic Sargassum spp. (sargasso) into the Mexican Caribbean Sea has caused major deterioration of the coastal environment and has affected the tourism industry as well as livelihoods since 2015. Species of Sargassum have high capacity to absorb metals; thus, leachates of sargasso may contribute to contamination by potentially toxic metals when they drain into the sea and into the groundwater when dumped in inadequate land deposits. Valorization of sargasso would contribute to sustainable management; therefore, knowledge on potentially toxic metal content is necessary to define possible uses of the algae. We present concentrations of 28 elements measured using a non-destructive X-ray fluorescence analyzer (XRF) in 63 samples of sargasso collected between August 2018 and June 2019 from eight localities along ∼370 km long coastline of the Mexican Caribbean Sea. The sargasso tissues contained detectable concentrations of Al, As, Ca, Cl, Cu, Fe, K, Mg, Mn, Mo, P, Pb, Rb, S, Si, Sr, Th, U, V, and Zn. The element concentration in sargasso varied on spatial and temporal scales, which likely depended on the previous trajectory of the pelagic masses, and whether these had (or had not) passed through contaminated areas. Total arsenic concentration varied between 24–172 ppm DW, exceeding the maximum limit for seaweed intended as animal fooder (40 ppm DW) in 86% of the samples. For valorization, we recommend analyses of metal contents as a mandatory practice or avoiding uses for nutritional purposes. The high arsenic content is also of concern for environmental contamination of the sea and aquifer.
Few at-sea behavioural data exist for oceanic-stage neonate sea turtles, a life-stage commonly referred to as the sea turtle 'lost years'. Historically, the long-term tracking of small, fast-growing organisms in the open ocean was logistically or technologically impossible. Here, we provide the first long-term satellite tracks of neonate sea turtles. Loggerheads (Caretta caretta) were remotely tracked in the Atlantic Ocean using small solar-powered satellite transmitters. We show that oceanic-stage turtles (i) rarely travel in Continental Shelf waters, (ii) frequently depart the currents associated with the North Atlantic Subtropical Gyre, (iii) travel quickly when in Gyre currents, and (iv) select sea surface habitats that are likely to provide a thermal benefit or refuge to young sea turtles, supporting growth, foraging and survival. Our satellite tracks help define Atlantic loggerhead nursery grounds and early loggerhead habitat use, allowing us to re-examine sea turtle 'lost years' paradigms.
Compared with our understanding of most aspects of sea turtle biology, knowledge of the surface-pelagic juvenile life stages remains limited. Young North Atlantic cheloniids (hard-shelled sea turtles) are closely associated with surface-pelagic drift communities (SPDCs), which are dominated by macroalgae of the genus Sargassum. We quantified SPDCs in the eastern Gulf of Mexico, a region that hosts four species of cheloniids during their surface-pelagic juvenile stage. Landsat satellite imagery was used to identify and measure the areal coverage of SPDCs in the eastern Gulf during 2003-2011 (1323 images). Although the SPDC coverage varied annually, seasonally, and spatially, SPDCs were present year-round, with an estimated mean area of SPDC in each Landsat image of 4.9 km
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(SD = 10.1). The area of SPDCs observed was inversely proportional to sea-surface wind velocity (Spearman's r = -0.33, p <; 0.001). The SPDC coverage was greatest during 2005, 2009, and 2011 and least during 2004 and 2010, but the 2010 analysis was affected by the Deepwater Horizon oil spill, which occurred within the study region. In the eastern Gulf, the area of SPDC peaked during June-August of each year. Although the SPDC coverage appeared lower in the eastern Gulf than in other regions of the Gulf and the North Atlantic, surface-pelagic juvenile green, hawksbill, Kemp's ridley, and loggerhead turtles were found to be using this habitat, suggesting that eastern Gulf SPDCs provide developmental habitats that are critical to the recovery of four sea turtle species.
Sargassum washing ashore on the beaches of the Caribbean Islands since 2011 has caused problems for the local environments, tourism, and economies. Although preliminary results of Sargassum distributions in the nearby oceans have been obtained using measurements from the Medium Resolution Imaging Spectrometer (MERIS), MERIS stopped functioning in 2012, and detecting and quantifying Sargassum distributions still face technical challenges due to ambiguous pixels from clouds, cloud shadows, cloud adjacency effect, and large-scale image gradient. In this paper, a novel approach is developed to detect Sargassum presence and to quantify Sargassum coverage using the Moderate Resolution Imaging Spectroradiometer (MODIS) alternative floating algae index (AFAI), which examines the red-edge reflectance of floating vegetation. This approach includes three basic steps: 1) classification of Sargassum-containing pixels through correction of large-scale gradient, masking clouds and cloud shadows, and removal of ambiguous pixels; 2) linear unmixing of Sargassum-containing pixels; and, 3) statistics of Sargassum area coverage in pre-defined grids at monthly, seasonal, and annual intervals. In the absence of direct field measurements to validate the results, limited observations from the Hyperspectral Imager for the Coastal Ocean (HICO) measurements and numerous local reports support the conclusion that the elevated AFAI signals are due to the presence of Sargassum instead of other floating materials, and various sensitivity analyses are used to quantify the uncertainties in the derived Sargassum area coverage. The approach was applied to MODIS observations between 2000 and 2015 over the Central West Atlantic (CWA) region (0–22°N, 63–38°W) to derive the spatial and temporal distribution patterns as well as the total area coverage of Sargassum. Results indicate that the first widespread Sargassum distribution event occurred in 2011, consistent with previous MERIS findings. Since 2011, only 2013 showed a minimal Sargassum coverage similar to the period of 2000 to 2010; all other years showed significantly more coverage. More alarmingly, the summer months of 2015 showed mean coverage of > 2000 km2, or about 4 times of the summer 2011 coverage and 20 times of the summer 2000 to 2010 coverage. Analysis of several environmental variables provided some hints on the reasons causing the inter-annual changes after 2010, yet further multi-disciplinary research (including in situ measurements) is required to understand such changes and long-term trends in Sargassum coverage.