Carlos M. Duarte’s research while affiliated with King Abdullah University of Science and Technology and other places

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Publications (199)


Average AGB losses range from 4.25 % to 9.25 %, and overall AGB from 9.96 % to 10.26 %
Projected impacts of future climate change on the aboveground biomass of seagrasses at global scale
  • Article

February 2025

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48 Reads

The Science of The Total Environment

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Carlos M Duarte

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Seagrasses are crucial marine ecosystems that have experienced declines due to anthropogenic and climate change impacts. The projected future climate change suggests additional seagrass losses, but no global-scale estimates are currently available on the potential changes in aboveground biomass of seagrasses. We modelled and quantified the current potential aboveground biomass (AGB) of seagrasses on the global scale and projected future AGB under contrasting Shared Socioeconomic Pathway (SSP) scenarios, from low emissions (SSP1–1.9) to high emissions (SSP3–7.0 and SSP5–8.5). A machine learning algorithm (Boosted Regression Trees) fitted a comprehensive AGB dataset against biological and anthropogenic meaningful predictors. The model performed with high accuracy (deviance explained: 0.83), highlighting the role of genus and temperature conditions in defining global AGB patterns. The model estimated a present-day average AGB of 133.83 gDW·m2 (DW, dry weight) and a total global AGB of 0.0673 Pg DW. Future projections were highly dependent on the emission scenario, with losses in AGB ranging between 4.25 % and 9.25 % and in overall AGB between 9.96 % and 10.26 % across scenarios. Particularly, the higher emission scenario projected severe regional losses along the coastlines of the Tropical Eastern Pacific, the Eastern Indo-Pacific, the Temperate Northern Pacific, and the Tropical Atlantic, and gains along the Temperate Southern Africa and the Arctic regions. Our global estimates underline that fulfilling the Paris Agreement, as well as conserving and monitoring populations most affected by combined anthropogenic pressures would help to limit seagrass AGB declines, thereby supporting the multiple ecological services of seagrasses.


Location of the sampled seaweed farms, the time (years) elapsed since the onset of farming and the size of the harvested area (ha)
The orange square in Asia shows the area highlighted in the insert. Shapefile of the world and countries sampled from www.naturalearthdata.com and ocean bathymetry from GEBCO www.gebco.net. See also Tables 1 and 2.
Duration of farming operation and sediment C accumulation
a,b, The relationship between the duration of farming operation and: the thickness of the sediment layer deposited (a); the Corg stock accumulated per unit farm area (b). Solid lines represent the fitted least-squares linear regression analysis equations: log10 accumulated sediment thickness (mm) = 0.06 + 1.39 (± 0.19) log10 farm age (yr) (R² = 0.84, F = 54.2, n = 12, P = 0.0000000543) (a); log10 Corg accumulated (tC ha⁻¹) = −0.96 + 1.21 (± 0.16) log10 farm age (yr) (R² = 0.61, F = 21.9, n = 16, P = 0.0004) (b).
Carbon burial and farm yield
a,b, The relationship between the Corg burial in sediments below the farm and the current farm yield (a) and the Corg burial in reference sediments (b). The solid line in a represents the fitted least-squares linear regression analysis equations—Corg burial (tC ha⁻¹ yr⁻¹) = 0.052 + 0.0114 (± 0.003) yield (t fw ha⁻¹ yr⁻¹) (R² = 0.52, F = 10.9, n = 12, P = 0.0078) and that in b shows the 1:1 line. Empty symbols in b denote farms where reference values were obtained from sediment layers deposited before farm operation.
Time of operation and carbon accumulation and burial rate in seaweed farms
General characteristics of the seaweed farms studed
Carbon burial in sediments below seaweed farms matches that of Blue Carbon habitats
  • Article
  • Full-text available

January 2025

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409 Reads

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1 Citation

Nature Climate Change

Carlos M. Duarte

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Seaweed farming has emerged as a potential Blue Carbon strategy, yet empirical estimates of carbon burial from such farms remain lacking in the literature. Here, we quantify carbon burial in 20 seaweed farms distributed globally, ranging from 2 to 300 years in operation and from 1 to 15,000 ha in size. The thickness of sediment layers and stocks of organic carbon accumulated below the farms increased with farm age, reaching 140 tC ha⁻¹ for the oldest farm. Organic carbon burial rates averaged 1.87 ± 0.73 tCO2e ha⁻¹ yr⁻¹ in farm sediments, twice that in reference sediments. The excess CO2e burial attributable to the seaweed farms averaged 1.06 ± 0.74 CO2e ha⁻¹ yr⁻¹, confirming that seaweed farming in depositional environments buries carbon in the underlying sediments at rates towards the low range of that of Blue Carbon habitats, but increasing with farm age.

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Dynamics of CO2 and CH4 fluxes in Red Sea mangrove soils

January 2025

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41 Reads

Red Sea mangroves have a lower carbon burial rate than the global average, whereby small greenhouse gas fluxes may offset a large proportion of carbon burial. Monthly soil core sampling was conducted across 2 years at two sites within a central eastern Red Sea mangrove stand to examine carbon dioxide (CO2) and methane (CH4) fluxes under dry and inundated conditions. Fluxes were highly variable, characterized by a prevalence of low emissions punctuated by bursts of high emissions. At the landward site, average ± SE (median) flux from the soil–air interface was 3111 ± 929 (811) µmol CO2 m⁻² d⁻¹ and 1.68 ± 0.63 (0.26) µmol CH4 m⁻² d⁻¹ under light conditions and 8657 ± 2269 (1615) µmol CO2 m⁻² d⁻¹ and 0.84 ± 0.79 (0.59) µmol CH4 m⁻² d⁻¹ under dark conditions. Average ± SE (median) sea–air fluxes were -55 ± 165 (-79) µmol CO2 m⁻² d⁻¹ and 0.12 ± 0.23 (0.08) µmol CH4 m⁻² d⁻¹ under light conditions and 27 ± 48 (53) µmol CO2 m⁻² d⁻¹ and 0.16 ± 0.13 (0.09) µmol CH4 m⁻² d⁻¹ in dark conditions. The seaward site recorded a higher CH4 flux, averaging 18.7 ± 8.18 (1.7) and 17.1 ± 4.55 (7.7) µmol CH4 m⁻² d⁻¹ in light and dark conditions. Mean fluxes offset 94.5 % of carbon burial, with a median of 4.9 % skewed by extreme variability. However, reported CO2 removal by total alkalinity emission from carbonate dissolution greatly exceeded both processes and drives the role of these ecosystems as intense CO2 sinks.


Seagrass arabinogalactan-proteins: Are they important for adaptation to the marine environment?

January 2025

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18 Reads

During the late cretaceous period several lineages of angiosperm plants transitioned from land to the sea by successfully adapting to life in salt water, forming the polyphyletic group of seagrasses. Today, four seagrass families inhabit coastal systems and are deeply intertwined with health and welfare of these ecosystems. Adaptation to the ocean environment included changes in the composition of plant cell walls and associated glycoproteins. We have asked the question whether or not there is a convergent and similar arabinogalactan-protein glycan repertoire in all seagrasses, given initial findings of arabinogalactan-proteins with unique features in the well-studied eelgrass, Zostera marina . We isolated and characterized arabinogalactan-proteins from seven species covering the four major seagrass families using carbohydrate analysis and glycan immunoassays, along with a bioinformatic search for relevant gene pathways in newly published seagrass genomes and transcriptomes. Glycan parts of all seagrass arabinogalactan-proteins shared a high proportion of 1,4-linked glucuronic acids and terminal 4- O -methyl glucuronic acid residues. Trait-based dendrograms generated to inform phylogenetic-relatedness showed there was no phylogenetic signal among seagrass families and arabinogalactan-protein features. Transcriptomic datasets from Cymodocea nodosa and Thalassia hemprichii growing under hypersaline conditions showed an upregulation of enzymes involved in 4 O -methylation and glucuronic acid transfer. We therefore conclude that environmental factors, especially salinity with higher monovalent ion concentration, influence seagrass arabinogalactan-proteins structure more intensely than phylogenetic history.


Ecological effects of micro/nanoplastics on plant-associated food webs

December 2024

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27 Reads

Trends in Plant Science

Micro/nanoplastics (MNPs) contamination is a potential threat to global biodiversity and ecosystem functions, with unclear ecological impacts on aboveground (AG) and belowground (BG) food webs in terrestrial ecosystems. Here, we discuss the uptake, ingestion, bioaccumulation, and ecotoxicological effects of MNPs in plants and associated AG-BG biota at various trophic levels. We propose key pathways for MNPs transfer between the AG-BG food webs and elaborate their impact on terrestrial ecosystem multifunctionality. We conclude that MNPs are bioaccumulated in most studied plants and associated AG-BG biota and can be transferred along AG-BG food webs, which may profoundly impact ecosystem functioning. However, most pathways are still untested. Future research on MNPs should focus on the interactions within AG-BG food webs in terrestrial ecosystems.


(A) Principal sites mentioned in the manuscript. NRS (Northern Red Sea), CRS (Central Red Sea), SRS (Southern Red Sea), this division follows the approach proposed by Wang et al.⁵⁰. (B) Spatial distribution of Selachii sightings and (C) spatial distribution of Batoidea sightings, with different colors representing various survey methods. Map created using Esri ArcGIS Pro version 2.6.0 (Esri, 2020).
Taxonomic distribution of Selachii recorded in our dataset across different families (A) and different genera (B).
Taxonomic distribution of Batoidea recorded in our dataset across different families (A) and different genera (B).
List of Batoidea identified at species level in the CERSE dataset.
An integrated multi-source dataset of elasmobranchs in the Red Sea following the Red Sea Decade Expedition

December 2024

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109 Reads

Scientific Data

Red Sea elasmobranch populations are facing alarming declines. Effective conservation efforts require management strategies informed by extensive datasets and by developing an understanding of distribution patterns within the basin, which is currently lacking. This study introduces CERSE (Central and Eastern Red Sea Elasmobranchs), a comprehensive compilation of elasmobranch observations in the central and eastern Red Sea basin following the route of the Red Sea Decade Expedition. The data set was curated from surveys conducted during two scientific cruises, a time-series survey within Red Sea Global project areas (Tabuk province), and observations extracted from peer-reviewed literature. Through the use of diverse methodologies, we provide a holistic view of elasmobranchs distribution in the region, for a total of 2,847 sightings recorded. By consolidating dispersed information from across the region, this dataset forms a comprehensive foundation for future research and monitoring endeavors focused on elasmobranch fauna, and will serve as a cornerstone for informing targeted conservation initiatives aimed at safeguarding endangered elasmobranch species in this region.


Resilience of Small Islands: Unveiling Nature-Based Solutions for Sustainable Futures

December 2024

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38 Reads

This chapter explores the inherent resilience of small islands in the face of multifaceted challenges and examines the pivotal role of nature-based solutions in securing their sustainable trajectories. Small islands, possessing unique ecosystems and cultural heritages, face heightened vulnerabilities due to their size, geographical isolation, and exposure to various environmental, social, and economic stressors. Amid these challenges, the concept of resilience emerges as a beacon of hope, representing the capacity of these islands to adapt, withstand, and transform. Drawing upon a comprehensive review of literature and case studies, this chapter investigates the diverse dimensions of resilience exhibited by small islands. It examines the intricate interplay between natural systems and human societies, showcasing how nature-based solutions serve as a catalyst for resilience-building. From leveraging ecosystem services to integrating traditional knowledge and innovative technologies, these solutions offer sustainable pathways that bolster the resilience of small islands. This chapter highlights the significance of nature-based approaches in mitigating the impacts of climate change, biodiversity loss, and socioeconomic vulnerabilities. It sheds light on successful initiatives and best practices, elucidating their contributions to enhancing adaptive capacities and fostering sustainable development in small island contexts. Furthermore, this chapter emphasizes the need for holistic and participatory approaches, engaging local communities, policymakers, and stakeholders in co-designing and implementing nature-based solutions. It advocates for the integration of indigenous wisdom, community-based management, and innovative strategies aligned with local contexts to amplify resilience efforts. Ultimately, this chapter aims to underscore the importance of nature-based solutions as indispensable tools in fortifying the resilience of small islands. By recognizing and harnessing the intrinsic capacities of ecosystems, societies, and cultures, it advocates for a paradigm shift toward sustainable futures, where small islands thrive in harmony with nature.



High resolution data reveal fundamental steps and turning points in animal movements

December 2024

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394 Reads

Animal movement paths display substantial complexity and variability, leading researchers to seek underlying rules that govern these patterns and mathematical models that best describe them. Using high-resolution (≥ 10 Hz) movement from 43 vertebrate species across diverse taxa, mass, and lifestyles, we show that movement paths are universally composed of straight-line steps interspersed with sharp turns, echoing a pattern documented for lower taxa such as bacteria. We report how these vertebrate ‘fundamental step lengths’ and ‘fundamental turn angles’, which are intrinsically different from the straight-line paths detailed in studies using low resolution position data, vary with species’ mass, lifestyle, behaviour, and environmental context. To explain these, we posit that animals inherently move in a straight line until sensory information signals a perceived better heading, which instigates a turn. The constellation of fundamental step lengths and turn angles over varying time intervals affects how well different models of animal movement (such as random walk or Lévy flight) fit lower resolution data. By examining turns as decision points, we can seek drivers of animal movement patterns and thereby work to predict future paths under varying conditions.


Green turtle tracking leads the discovery of seagrass blue carbon resources

November 2024

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143 Reads

Seagrass meadows are natural carbon sinks, and their conservation and restoration play a crucial role in climate change mitigation and adaptation. However, blue carbon projects are hindered, in most nations, by major gaps in understanding the distribution and extent of seagrasses. Here, we show how satellite tracking of green turtles (Chelonia mydas) provided a major advance in identifying novel seagrass blue carbon resources in the Red Sea. By tracking 53 nesting green turtles, we identified 38 distinctive foraging sites. All ground-truthed foraging sites (100%) identified a seagrass meadow, surpassing the 40% (n = 30) accuracy of satellite imagery-based inferences. Sampling from these turtle-derived locations represents a greater range of depths than previously sampled in the Red Sea providing a carbon stock estimate of 4.89 ± 0.83 kg Corg (organic carbon) m⁻². By improving estimates of seagrass extent and associated blue carbon, our approach can support the conservation of blue carbon resources in data-deficient regions worldwide.


Citations (56)


... Therefore because most oil and gas in wind infrastructure is less than 200 m deep, seaweed must be transported offshore by ocean currents to the deep ocean to be sequestered. Seaweed farms placed over a depositional environment can contribute to carbon sequestration [43]. However, since seaweed farms on offshore infrastructure will be subject to wave action and ocean currents, a substantial amount of carbon will be exported from the site. ...

Reference:

Global potential for seaweed aquaculture on existing offshore infrastructure
Carbon burial in sediments below seaweed farms matches that of Blue Carbon habitats

Nature Climate Change

... Veamos un ejemplo concreto. La Gran Muralla Verde para el Sahel y el Sahara (GGWSS) es un proyecto ambicioso que busca combatir la desertificación y la sequía en esas regiones del norte de África (Blanco-Sacristán et al., 2024). El plan tiene objetivos loables, como restaurar 100 millones de hectáreas de tierra degradada y crear 10 millones de empleos verdes para 2030. ...

The Middle East as a Natural Laboratory to Advance Our Understanding of Global Hyper-Arid Drylands

Cambridge Prisms: Drylands

... Global supply chains may also be affected by the decline of nature (Becken & Ren, 2012;Duarte et al., 2024), as disruptions in the availability of natural resources can result in price increases and shortages of products and services. For instance, delays in production and increased costs for manufacturers may result from disruptions in the supply of raw materials because of environmental degradation (Bell et al., 2012;Davis et al., 2020;Paul et al., 2017). ...

Advancing Global Climate and Biodiversity Goals Through Regenerative Tourism

Sustainability

... Despite extensive research, the etiology and pathogenesis of FP are not fully understood. FP continues to be observed in new geographic marine areas, likely due to the circum-tropical or highly migratory nature of sea turtle species and to climate change impacts profoundly altering the global oceanic hydrological cycle, shifting and expanding the spatial patterns of terrestrial and aquatic infectious diseases globally (Abreu-Grobois et al., 2008;Burge & Hershberger, 2020;Casale & Tucker, 2017;Christiaanse et al., 2024;Cooley et al., 2022;Du et al., 2019;IPCC Annex V, 2022;James et al., 2021;Lafferty, 2009;Loganathan et al., 2021;Manes, Carthy, et al., 2023;Mortimer et al., 2008;Mycoo et al., 2022;Origlia et al., 2023;Parmesan et al., 2022;Patricio et al., 2012;Red List Standards & Petitions Subcommittee, 1996;Robben et al., 2023;Saladin & Freggi, 2024, Table 1; Seminoff, 2023;Wallace et al., 2013;Whilde et al., 2024;Wibbels & Bevan, 2019;Yetsko et al., 2020). Monitoring methods of FP and its putative etiological agent, alpha chelonid herpesvirus 5 (ChHV5), suffer from sparse, potentially biased, geographically limited, and unhomogenised approaches. ...

Distribution of global sea turtle nesting explained from regional-scale coastal characteristics

... Source: RICCAR (2017). Note: The two future periods (2046-2065 and 2081-2100) The 2023 Climate Futures Report "Saudi Arabia in a 3-Degrees Warmer World" forecasts some of the potential consequences arising from this possible climate trajectory by the end of the century and discusses how to avoid some of the potential climate outcomes that such a future might impose (McCabe et al. 2023). Furthermore, this study encourages "informed decision-making processes, ...

Climate Futures Report: Saudi Arabia in a 3-degrees warmer world

... The role of seaweed is also significant in environmental protection. During growth, seaweeds can absorb nutrients such as nitrogen and phosphorus to repair eutrophication in nearshore waters Zheng, Jin, et al. 2019) and alleviate the HABs problem (Zhu et al. 2022). They can also mitigate ocean acidification (Xiao et al. 2021), adsorb heavy metals (e.g. ...

Dynamics of phytoplankton community in relation to seasonal variation and Laminaria japonica culturing in coastal area
  • Citing Article
  • September 2022

Estuarine Coastal and Shelf Science

... This is the case of Sardinia biodiversity in general, and the Montiferru-Sinis coastal zones located along the western coast of Sardinia (Italy), representing an area historically far from both mainstream access and the scientific community, thus overlooked by marine biodiversity research. This area is rarely considered, excluding recent spotted opportunistic reports and little manipulative experiments (Grech et al. 2019;Garrabou et al. 2022;Grech & Masala, 2023;Ragkousis et al. 2023). ...

Marine heatwaves drive recurrent mass mortalities in the Mediterranean Sea

... Marine heatwaves (MHWs)-extended periods of anomalously warm ocean temperatures-are becoming increasingly common (Oliver et al. 2018), often leading to catastrophic consequences for marine communities (Hoegh-Guldberg et al. 2007;Smale et al. 2019). While most of the detrimental impacts of MHWs have been recorded in benthic communities (Giraldo-Ospina, Kendrick, and Hovey 2020; Garrabou et al. 2022;Smith et al. 2023), mass mortalities of pelagic fish and megafauna have been documented (Cavole et al. 2016;Wild et al. 2019;Trainer et al. 2020), facilitated by deoxygenation or harmful algal blooms. In the northern Gulf of Aqaba, a mass mortality of over 40 species of reef fish was recorded between June and August 2017, during a MHW event with an extreme increase of 4.2°C in 2.5 days (Genin et al. 2020). ...

Marine heatwaves drive recurrent mass mortalities in the Mediterranean Sea
  • Citing Article
  • July 2022

... On an annual basis, increased surface chlorophyll amplifies the seasonal cycle of upper-ocean temperature by about 0.4°C in the Mediterranean and 0.8°C in the Black Sea. This result suggests that accounting for changes in water clarity in ocean models could be crucial for predicting temperature extremes and marine heatwaves, which are known to have negative ecological impacts (e.g., Garrabou et al., 2022). The heat budget analyses indicated that the SST response to chlorophyll variations is determined by the mixed layer depth and a subtle interplay between the warming effect of solar radiation and the indirect cooling caused by vertical turbulent mixing. ...

Marine heatwaves drive recurrent mass mortalities in the Mediterranean Sea

Global Change Biology

... Great strides have been made to counteract these knowledge gaps, including through species auditioning (e.g., Fetterplace et al., 2022;Parmentier et al., 2011), field observations (e.g., Tricas & Boyle, 2014), reviews of select taxa or regions (e.g., Colleye & Parmentier, 2012;Parmentier et al., 2021), and the creation of inventories of fish sound production knowledge . Tropical coral reefs are now among the most common habitats sampled in marine soundscape studies (Havlik et al., 2022) and acoustic monitoring is increasingly being incorporated into marine management strategies (e.g., McKenna et al., 2021). Awareness of fish sound production has been further advanced globally, for example through numerous calls for comprehensive repositories of underwater sound recordings such as a global library of underwater biological sounds (GLUBS; Parsons et al., 2022) or the Sea Sounds Portal (KAUST, 2024), though these aspirations ...

State of Play in Marine Soundscape Assessments