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Recent Submissions

  • Global beta diversity patterns of microbial communities in the surface and deep ocean

    Villarino, Ernesto; Watson, James R.; Chust, Guillem; Woodill, A. John; Klempay, Benjamin; Jonsson, Bror; Gasol, Josep M.; Logares, Ramiro; Massana, Ramon; Giner, Caterina R; Salazar, Guillem; Álvarez-Salgado, Xosé Antón; Catala, Teresa S.; Duarte, Carlos M.; Agusti, Susana; Mauro, Francisco; Irigoien, Xabier; Barton, Andrew D. (Global Ecology and Biogeography, Wiley, 2022-08-11) [Article]
    Aim Dispersal and environmental gradients shape marine microbial communities, yet the relative importance of these factors across taxa with distinct sizes and dispersal capacity in different ocean layers is unknown. Here, we report a comparative analysis of surface and deep ocean microbial beta diversity and examine how these patterns are tied to oceanic distance and environmental gradients. Location Tropical and subtropical oceans (30°N–40°S). Time period 2010–2011. Major taxa studied Prokaryotes and picoeukaryotes (eukaryotes between 0.2 and 3 μm). Methods Beta diversity was calculated from metabarcoding data on prokaryotic and picoeukaryotic microbes collected during the Malaspina expedition across the tropical and subtropical oceans. Mantel correlations were used to determine the relative contribution of environment and oceanic distance driving community beta diversity. Results Mean community similarity across all sites for prokaryotes was 38.9% in the surface and 51.4% in the deep ocean, compared to mean similarity of 25.8 and 12.1% in the surface and deep ocean, respectively, for picoeukaryotes. Higher dispersal rates and smaller body sizes of prokaryotes relative to picoeukaryotes likely contributed to the significantly higher community similarity for prokaryotes compared with picoeukaryotes. The ecological mechanisms determining the biogeography of microbes varied across depth. In the surface ocean, the environmental differences in space were a more important factor driving microbial distribution compared with the oceanic distance, defined as the shortest path between two sites avoiding land. In the deep ocean, picoeukaryote communities were slightly more structured by the oceanic distance, while prokaryotes were shaped by the combined action of oceanic distance and environmental filtering. Main conclusions Horizontal gradients in microbial community assembly differed across ocean depths, as did mechanisms shaping them. In the deep ocean, the oceanic distance and environment played significant roles driving microbial spatial distribution, while in the surface the influence of the environment was stronger than oceanic distance.
  • Investigating calcification-related candidates in a non-symbiotic scleractinian coral, Tubastraea spp.

    Capasso, Laura; Aranda, Manuel; Cui, Guoxin; Pousse, Melanie; Tambutté, Sylvie; Zoccola, Didier (Scientific Reports, Springer Science and Business Media LLC, 2022-08-06) [Article]
    In hermatypic scleractinian corals, photosynthetic fixation of CO2 and the production of CaCO3 are intimately linked due to their symbiotic relationship with dinoflagellates of the Symbiodiniaceae family. This makes it difficult to study ion transport mechanisms involved in the different pathways. In contrast, most ahermatypic scleractinian corals do not share this symbiotic relationship and thus offer an advantage when studying the ion transport mechanisms involved in the calcification process. Despite this advantage, non-symbiotic scleractinian corals have been systematically neglected in calcification studies, resulting in a lack of data especially at the molecular level. Here, we combined a tissue micro-dissection technique and RNA-sequencing to identify calcification-related ion transporters, and other candidates, in the ahermatypic non-symbiotic scleractinian coral Tubastraea spp. Our results show that Tubastraea spp. possesses several calcification-related candidates previously identified in symbiotic scleractinian corals (such as SLC4-γ, AMT-1like, CARP, etc.). Furthermore, we identify and describe a role in scleractinian calcification for several ion transporter candidates (such as SLC13, -16, -23, etc.) identified for the first time in this study. Taken together, our results provide not only insights about the molecular mechanisms underlying non-symbiotic scleractinian calcification, but also valuable tools for the development of biotechnological solutions to better control the extreme invasiveness of corals belonging to this particular genus.
  • A new species of Bathypathes (Cnidaria, Anthozoa, Antipatharia, Schizopathidae) from the Red Sea and its phylogenetic position

    Chimienti, Giovanni; Terraneo, Tullia Isotta; Vicario, Silvia; Marchese, Fabio; Purkis, Sam J.; Abdulla Eweida, Ameer; Rodrigue, Mattie; Benzoni, Francesca (ZooKeys, Pensoft Publishers, 2022-08-04) [Article]
    A black coral, Bathypathes thermophila Chimienti, sp. nov. is described from the Saudi Arabian coasts of the Gulf of Aqaba and north Red Sea (Neom area) using an integrated taxonomic approach. The morphological distinctiveness of the new species is confirmed by molecular analyses. The species thrives in warm and high salinity waters typical of the Red Sea at bathyal depths. It can form colony aggregations on muddy bottoms with scattered, small hard substrates. Colonies are monopodial, feather-like, and attached to a hard substrate through a thorny basal plate. Pinnules are simple, arranged biserially and alternately, and all the same length (up to approximately 20 cm) except for few, proximal ones. Spines are triangular, laterally compressed, subequal, smooth, and simple or rarely bifurcated. Polyps are elongated transversely, 1.5–2.0 mm in transverse diameter. Large colonies can have one or few branches, whose origin is discussed. The phylogenetic position of B. thermophila sp. nov. within the order Antipatharia, recovered using three mitochondrial markers, shows that it is nested within the family Schizopathidae. It is close to species in the genera Parantipathes, Lillipathes, Alternatipathes, and Umbellapathes rather than to the other available representatives of the genus Bathypathes, as currently defined based on morphology. In agreement with previous findings, our results question the evolutionary significance of morphological characters traditionally used to discriminate Antipatharia at higher taxonomic level.
  • Increased incompatibility of heterologous algal symbionts under thermal stress in the cnidarian-dinoflagellate model Aiptasia

    Cziesielski, Maha Joana; Liew, Yi Jin; Cui, Guoxin; Aranda, Manuel (Communications Biology, Springer Science and Business Media LLC, 2022-07-28) [Article]
    Rising ocean temperatures are increasing the rate and intensity of coral mass bleaching events, leading to the collapse of coral reef ecosystems. To better understand the dynamics of coral-algae symbioses, it is critical to decipher the role each partner plays in the holobiont’s thermotolerance. Here, we investigated the role of the symbiont by comparing transcriptional heat stress responses of anemones from two thermally distinct locations, Florida (CC7) and Hawaii (H2) as well as a heterologous host-symbiont combination composed of CC7 host anemones inoculated with the symbiont Breviolum minutum (SSB01) from H2 anemones (CC7-B01). We find that oxidative stress and apoptosis responses are strongly influenced by symbiont type, as further confirmed by caspase-3 activation assays, but that the overall response to heat stress is dictated by the compatibility of both partners. Expression of genes essential to symbiosis revealed a shift from a nitrogen- to a carbon-limited state only in the heterologous combination CC7-B01, suggesting a bioenergetic disruption of symbiosis during stress. Our results indicate that symbiosis is highly fine-tuned towards particular partner combinations and that heterologous host-symbiont combinations are metabolically less compatible under stress. These results are essential for future strategies aiming at increasing coral resilience using heterologous thermotolerant symbionts.
  • Novel Interactions Between Phytoplankton and Bacteria Shape Microbial Seasonal Dynamics in Coastal Ocean Waters

    Arandia-Gorostidi, Nestor; Krabberød, Anders K.; Logares, Ramiro; Deutschmann, Ina Maria; Scharek, Renate; Moran, Xose Anxelu G.; González, Felipe; Alonso-Sáez, Laura (Frontiers in Marine Science, Frontiers Media SA, 2022-07-22) [Article]
    Trophic interactions between marine phytoplankton and heterotrophic bacteria are at the base of the biogeochemical carbon cycling in the ocean. However, the specific interactions taking place between phytoplankton and bacterial taxa remain largely unexplored, particularly out of phytoplankton blooming events. Here, we applied network analysis to a 3.5-year time-series dataset to assess the specific associations between different phytoplankton and bacterial taxa along the seasonal scale, distinguishing between free-living and particle-attached bacteria. Using a newly developed network post-analysis technique we removed bacteria-phytoplankton correlations that were primarily driven by environmental parameters, to detect potential biotic interactions. Our results indicate that phytoplankton dynamics may be a strong driver of the inter-annual variability in bacterial community composition. We found the highest abundance of specific bacteria-phytoplankton associations in the particle-attached fraction, indicating a tighter bacteria-phytoplankton association than in the free-living fraction. In the particle-associated fraction we unveiled novel potential associations such as the one between Planctomycetes taxa and the diatom Leptocylindrus spp. Consistent correlations were also found between free-living bacterial taxa and different diatoms, including novel associations such as those between SAR11 with Naviculales diatom order, and between Actinobacteria and Cylindrotheca spp. We also confirmed previously known associations between Rhodobacteraceae and Thalassiosira spp. Our results expand our view on bacteria-phytoplankton associations, suggesting that taxa-specific interactions may largely impact the seasonal dynamics of heterotrophic bacterial communities.
  • Harnessing the microbiome to prevent global biodiversity loss

    Peixoto, Raquel S; Voolstra, Christian R.; Sweet, Michael; Duarte, Carlos M.; Carvalho, Susana; Villela, Helena D. M.; Lunshof, Jeantine E.; Gram, Lone; Woodhams, Douglas C.; Walter, Jens; Roik, Anna Krystyna; Hentschel, Ute; Thurber, Rebecca Vega; Daisley, Brendan; Ushijima, Blake; Daffonchio, Daniele; Costa, Rodrigo; Keller-Costa, Tina; Bowman, Jeff S.; Rosado, Alexandre S.; Reid, Gregor; Mason, Christopher E.; Walke, Jenifer B.; Thomas, Torsten; Berg, Gabriele (Nature Microbiology, Springer Science and Business Media LLC, 2022-07-21) [Article]
    Global biodiversity loss and mass extinction of species are two of the most critical environmental issues the world is currently facing, resulting in the disruption of various ecosystems central to environmental functions and human health. Microbiome-targeted interventions, such as probiotics and microbiome transplants, are emerging as potential options to reverse deterioration of biodiversity and increase the resilience of wildlife and ecosystems. However, the implementation of these interventions is urgently needed. We summarize the current concepts, bottlenecks and ethical aspects encompassing the careful and responsible management of ecosystem resources using the microbiome (termed microbiome stewardship) to rehabilitate organisms and ecosystem functions. We propose a real-world application framework to guide environmental and wildlife probiotic applications. This framework details steps that must be taken in the upscaling process while weighing risks against the high toll of inaction. In doing so, we draw parallels with other aspects of contemporary science moving swiftly in the face of urgent global challenges.
  • Sinking seaweed in the deep ocean for carbon neutrality is ahead of science and beyond the ethics

    Ricart, Aurora M; Krause-Jensen, Dorte; Hancke, Kasper; Price, Nichole N; Masque, Pere; Duarte, Carlos M. (Environmental Research Letters, IOP Publishing, 2022-07-21) [Article]
    Sinking vast amounts of seaweed in the deep ocean is currently being proposed as a promising ocean carbon dioxide removal strategy as well as a natural-based solution to mitigate climate change. Still, marketable carbon offsets through large-scale seaweed sinking in the deep ocean lack documentation and could involve unintended environmental and social consequences. Managing the risks requires a number of urgent actions.
  • Marine heatwaves drive recurrent mass mortalities in the Mediterranean Sea

    Garrabou, Joaquim; Gómez-Gras, Daniel; Medrano, Alba; Cerrano, Carlo; Ponti, Massimo; Schlegel, Robert; Bensoussan, Nathaniel; Turicchia, Eva; Sini, Maria; Gerovasileiou, Vasilis; Teixido, Nuria; Mirasole, Alice; Tamburello, Laura; Cebrian, Emma; Rilov, Gil; Ledoux, Jean-Baptiste; Souissi, Jamila Ben; Khamassi, Faten; Ghanem, Raouia; Benabdi, Mouloud; Grimes, Samir; Ocaña, Oscar; Bazairi, Hocein; Hereu, Bernat; Linares, Cristina; Kersting, Diego Kurt; la Rovira, Graciel; Ortega, Júlia; Casals, David; Pagès-Escolà, Marta; Margarit, Núria; Capdevila, Pol; Verdura, Jana; Ramos, Alfonso; Izquierdo, Andres; Barbera, Carmen; Rubio-Portillo, Esther; Anton, Irene; López-Sendino, Paula; Díaz, David; Vazquez-Luis, Maite; Duarte, Carlos M.; Marbà, Núria; Aspillaga, Eneko; Espinosa, Free; Grech, Daniele; Guala, Ivan; Azzurro, Ernesto; Farina, Simone; Cristina Gambi, Maria; Chimienti, Giovanni; Montefalcone, Monica; Azzola, Annalisa; Mantas, Torcuato Pulido; Fraschetti, Simonetta; Ceccherelli, Giulia; Kipson, Silvija; Bakran-Petricioli, Tatjana; Petricioli, Donat; Jimenez, Carlos; Katsanevakis, Stelios; Kizilkaya, Inci Tuney; Kizilkaya, Zafer; Sartoretto, Stephane; Elodie, Rouanet; Ruitton, Sandrine; Comeau, S.; Gattuso, Jean-Pierre; Harmelin, Jean-Georges (Global Change Biology, Wiley, 2022-07-18) [Article]
    Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change.
  • Demographic histories shape population genomics of the common coral grouper (Plectropomus leopardus)

    Payet, Samuel D.; Pratchett, M. S.; Saenz-Agudelo, P.; Berumen, Michael L.; DiBattista, Joseph; Harrison, H. B. (Evolutionary Applications, Wiley, 2022-07-17) [Article]
    Many coral reef fishes display remarkable genetic and phenotypic variation across their geographic ranges. Understanding how historical and contemporary processes have shaped these patterns remains a focal question in evolutionary biology, since they reveal how diversity is generated and how it may respond to future environmental change. Here we compare the population genomics and demographic histories of a commercially and ecologically important coral reef fish, the common coral grouper (Plectropomus leopardus [Lacépède 1802]), across two adjoining regions (the Great Barrier Reef; GBR, and the Coral Sea, Australia) spanning approximately 14 degrees of latitude and 9 degrees of longitude. We analysed 4,548 single nucleotide polymorphism (SNP) markers across 11 sites and show that genetic connectivity between regions is low, despite their relative proximity (~ 100 km) and an absence of any obvious geographic barrier. Inferred demographic histories using 10,479 markers suggest that the Coral Sea population was founded by a small number of GBR individuals and that divergence occurred ~ 190 kya under a model of isolation with asymmetric migration. We detected population expansions in both regions, but estimates of contemporary effective population sizes were approximately 50 % smaller in Coral Sea sites, which also had lower genetic diversity. Our results suggest that P. leopardus in the Coral Sea have experienced a long period of isolation that precedes the recent glacial period (~ 10 – 120 kya) and may be vulnerable to localised disturbances due to their relative reliance on local larval replenishment. While it is difficult to determine the underlying events that led to the divergence of Coral Sea and GBR lineages, we show that even geographically proximate populations of a widely dispersed coral reef fish can have vastly different evolutionary histories.
  • Greater functional diversity and redundancy of coral endolithic microbiomes align with lower coral bleaching susceptibility

    Cardenas, Anny; Raina, Jean-Baptiste; Pogoreutz, Claudia; Radecker, Nils; Bougoure, Jeremy; Guagliardo, Paul; Pernice, Mathieu; Voolstra, Christian R. (The ISME Journal, Springer Science and Business Media LLC, 2022-07-15) [Article]
    The skeleton of reef-building coral harbors diverse microbial communities that could compensate for metabolic deficiencies caused by the loss of algal endosymbionts, i.e., coral bleaching. However, it is unknown to what extent endolith taxonomic diversity and functional potential might contribute to thermal resilience. Here we exposed Goniastrea edwardsi and Porites lutea, two common reef-building corals from the central Red Sea to a 17-day long heat stress. Using hyperspectral imaging, marker gene/metagenomic sequencing, and NanoSIMS, we characterized their endolithic microbiomes together with 15N and 13C assimilation of two skeletal compartments: the endolithic band directly below the coral tissue and the deep skeleton. The bleaching-resistant G. edwardsi was associated with endolithic microbiomes of greater functional diversity and redundancy that exhibited lower N and C assimilation than endoliths in the bleaching-sensitive P. lutea. We propose that the lower endolithic primary productivity in G. edwardsi can be attributed to the dominance of chemolithotrophs. Lower primary production within the skeleton may prevent unbalanced nutrient fluxes to coral tissues under heat stress, thereby preserving nutrient-limiting conditions characteristic of a stable coral-algal symbiosis. Our findings link coral endolithic microbiome structure and function to bleaching susceptibility, providing new avenues for understanding and eventually mitigating reef loss.
  • Benthic Habitat Mapping of Thuwal’s Reefs Using High-Resolution Acoustic Technologies and Imaging Data

    Watts, Marta A. Ezeta (2022-07-14) [Thesis]
    Advisor: Benzoni, Francesca
    Committee members: Berumen, Michael L.; Volker, Vahrenkamp
    Remote sensing studies based on satellite and aerial imagery have improved our understanding of the morphology and distribution of several shallow reefs along the Red Sea Arabian coast and of the benthic assemblages associated to them (Bruckner et al., 2011; Bruckner et al., 2012; Rowlands et al., 2016). However, data concerning the deeper benthic assemblages' composition and spatial distribution in the central Red Sea are still missing. Using high-resolution acoustic technology and an underwater remotely operated vehicle (ROV), we aim to map, describe, and classify the reefs found in Thuwal's coastal area, filling the information gap by producing the first benthic habitat map of this area and making progress towards the evaluation of shallow and upper mesophotic benthic resources in the Saudi Arabian Red Sea. High-resolution acoustic data was collected using a multibeam echosounder system, which generated a bathymetric model. Based on this, the seafloor features were classified into 12 morphotypes following a visual assessment. Based on the morphotypes classification, 28 sites were visually selected for ground-truthing data acquisition and characterization of the substrate and benthic assemblages using a remotely operated vehicle equipped with an ultra-short baseline (USBL) positioning system. With the information obtained from the bathymetry data and the ROV video transects, a Top-Down approach in which we analyzed, categorized, and classified the data was used to create Thuwal's reefs benthic habitat map in which 23 different benthic habitat types were identified. This research uncovered previously poorly studied reef morphologies in the Red Sea and their associated benthic assemblages. Moreover, this work will help improve the understanding of the spatial distribution of benthic communities located on Thuwal's reefs, giving a baseline with the potential to provide fundamental information that can be used for mapping, management, conservation, and future research at other Red Sea reef sites in Saudi Arabia.
  • A novel feeding association between blackeye thicklip wrasse (Hemigymnus melapterus) and lyretail hogfish (Bodianus anthioides)

    He, Song; Berumen, Michael L. (Marine Biodiversity, Springer Science and Business Media LLC, 2022-07-13) [Article]
  • eDNA Reveals the Associated Metazoan Diversity of Mediterranean Seagrass Sediments

    Wesselmann, Marlene; Geraldi, Nathan; Marbà, Núria; Hendriks, Iris E; Diaz Rua, Ruben; Duarte, Carlos M. (Diversity, MDPI AG, 2022-07-08) [Article]
    Anthropogenic impacts on marine ecosystems have led to a decline of biodiversity across the oceans, threatening invaluable ecosystem services on which we depend. Ecological temporal data to track changes in diversity are relatively rare, and the few long-term datasets that exist often only date back a few decades or less. Here, we use eDNA taken from dated sediment cores to investigate changes over approximately the last 100 years of metazoan communities in native (Cymodocea nodosa and Posidonia oceanica) and exotic (Halophila stipulacea) seagrass meadows within the eastern Mediterranean Sea, at two locations in Greece and two in Cyprus. Overall, metazoan communities showed a high turnover of taxa during the past century, where losses of individual taxa in a seagrass meadow were compensated by the arrival of new taxa, probably due to the arrival of exotic species introduced in the Mediterranean Sea from the Suez Canal or the Gibraltar Strait. Specifically, bony fishes (Class Actinopteri) and soft corals (Class Anthozoa) presented significantly higher richness in the past (before the 1980s) than in the most recent time periods (from 1980–2017) and some Cnidarian orders were solely found in the past, whereas sponges and Calanoids (Class Hexanauplia), an order of copepods, showed an increase in richness since the 1980s. Moreover, the Phyla Porifera, Nematoda and the Classes Staurozoa, Hydrozoa and Ophiuroidea were detected in P. oceanica meadows but not in C. nodosa and H. stipulacea, which led to P. oceanica meadows having twice the richness of other seagrasses. The greater richness resulted from the more complex habitat provided by P. oceanica. The combination of eDNA and sediment cores allowed us to reconstruct temporal patterns of metazoan community diversity and provides a novel approach to follow natural communities back in time in the absence of time series and baseline data. The ongoing loss of P. oceanica meadows, likely to be compounded with future warming, might lead to a major loss of biodiversity and the replacement by other seagrass species, whether native or exotic, does not compensate for the loss.
  • Methods and Strategies to Uncover Coral-Associated Microbial Dark Matter

    Schultz, Junia; Modolon, Flúvio; Rosado, Alexandre S.; Voolstra, Christian R.; Sweet, Michael; Peixoto, Raquel S (mSystems, American Society for Microbiology, 2022-07-05) [Article]
    The vast majority of environmental microbes have not yet been cultured, and most of the knowledge on coral-associated microbes (CAMs) has been generated from amplicon sequencing and metagenomes. However, exploring cultured CAMs is key for a detailed and comprehensive characterization of the roles of these microbes in shaping coral health and, ultimately, for their biotechnological use as, for example, coral probiotics and other natural products. Here, the strategies and technologies that have been used to access cultured CAMs are presented, while advantages and disadvantages associated with each of these strategies are discussed. We highlight the existing gaps and potential improvements in culture-dependent methodologies, indicating several possible alternatives (including culturomics and in situ diffusion devices) that could be applied to retrieve the CAM “dark matter” (i.e., the currently undescribed CAMs). This study provides the most comprehensive synthesis of the methodologies used to recover the cultured coral microbiome to date and draws suggestions for the development of the next generation of CAM culturomics.
  • Physical forcing of phytoplankton dynamics in the Al-Wajh lagoon (Red Sea)

    Zhan, Peng; Krokos, Georgios; Gittings, John; Raitsos, Dionysios E.; Guo, Daquan; Papagiannopoulos, Nikolaos; Hoteit, Ibrahim (Limnology and Oceanography Letters, Wiley, 2022-07-05) [Article]
    Coastal lagoons are biodiversity hotspots that support neighboring ecosystems and various services. They can exhibit distinct biophysical characteristics compared to the adjacent open sea and act paradoxically as autonomous ecosystems. Using remotely sensed observations and state-of-the-art numerical simulations, the role of water column hydrodynamics in shaping the seasonal succession of phytoplankton biomass was investigated for a non-estuarine coastal lagoon situated in the northeastern Red Sea. Observations reveal that seasonal phytoplankton blooms inside the lagoon occur during a distinctively different period compared to the adjacent open sea. We provide evidence that this striking difference is due to the contrasting hydrodynamic conditions between inside and outside the lagoon, through their effects on stratification that regulate nutrient availability and hence favorable conditions to sustain rapid phytoplankton growth. The proposed mechanism may offer new insights into understanding the biophysical dynamics of non-estuarine coastal lagoons in other tropical regions of the global oceans.
  • Newly described nesting sites of the green sea turtle (Chelonia mydas) and the hawksbill sea turtle (Eretmochelys imbricata) in the central Red Sea

    Scott, Kirsty; Tanabe, Lyndsey K.; Miller, Jeffrey D.; Berumen, Michael L. (PeerJ, PeerJ, 2022-07-01) [Article]
    Background: There is relatively little published information about sea turtle nesting distribution and seasonality in the Saudi Arabian Red Sea. Upcoming large-scale developments occurring along the Saudi Arabian Red Sea coast could negatively affect many sea turtle nesting beaches with potential impacts on the survival of local populations. Methods: In 2019, two coastal beaches and three near-shore islands were surveyed for turtle nesting in the central Red Sea. We recorded all emergences, examined beach morphology, and collected sand samples to determine grain size, moisture content and colour. Results: Sea turtle nesting was found at all surveyed sites, though emergence counts were often low. The limited occurrence of nesting at several previously undocumented sites suggests that nesting activity may be widespread, but sparsely distributed, in the central Red Sea region. In addition, nesting at novel sites appeared to favour the seaward side of islands, a pattern that was not observed in previously documented areas. The substrate of most surveyed sites was composed of calcium carbonate with Ras Baridi as the only exception; it was composed of dark quartz-rich sediment. This study highlights several important sea turtle rookeries while also demonstrating that low levels of nesting occur throughout the region, although inter-annual nesting patterns still need to be determined. Future developments should be steered away from key nesting areas and the seaward bias in marginal rookeries should be taken into account where possible.
  • Foraging Ecology of Megaherbivores and Seagrass Distribution in Al-Wajh Lagoon

    Nasif, Areen O. (2022-07) [Thesis]
    Advisor: Berumen, Michael L.
    Committee members: Cochran, Jesse; Brainard, Rusty
    Seagrass meadows are a crucial foraging habitat for marine megaherbivores. The Red Sea hosts two megaherbivore species, the green turtle Chelonia mydas and the dugong Dugong dugon, along with twelve seagrass species. Seagrass habitats in the Saudi Arabian coast of the Red Sea are currently under pressure from large scale coastal developments. I used multiple methods to assess seagrass and megaherbivore densities in Al-Wajh lagoon, a unique semi-enclosed bay on the northeastern coast of the Red Sea that is currently targeted for development. Seagrasses were assessed using quadrat surveys while megaherbivores censuses were conducted by both unmanned aerial vehicles (UAV) and boat-based observers. Both seagrass and sea turtles were patchily distributed throughout the bay. Dugongs were never encountered during surveys but feeding trails and off-effort encounters suggest at least occasional use of the area. While there were some qualitative patterns between seagrass composition and feeding trail/sea turtle abundance, there was not enough data to achieve statistical significance. The UAV generally outperformed boat-based surveys, but the inability of the drone to distinguish turtles through dense seagrass coverage is a methodological limitation that should be overcome by using hyperspectral cameras in future work. Overall, my results highlight the importance of ground truthing habitat maps, reveal interesting questions for additional study, and provide some direction for future research and conservation efforts within Al-Wajh Lagoon.
  • Mangrove distribution and afforestation potential in the Red Sea

    Blanco Sacristan, Javier; Johansen, Kasper; Duarte, Carlos M.; Daffonchio, Daniele; Hoteit, Ibrahim; McCabe, Matthew (Science of The Total Environment, Elsevier BV, 2022-06-30) [Article]
    Mangrove ecosystems represent one of the most effective natural environments for fixing and storing carbon (C). Mangroves also offer significant co-benefits, serving as nurseries for marine species, providing nutrients and food to support marine ecosystems, and stabilizing coastlines from erosion and extreme events. Given these considerations, mangrove afforestation and associated C sequestration has gained considerable attention as a nature-based solution to climate adaptation (e.g., protect against more frequent storm surges) and mitigation (e.g. offsetting other C-producing activities). To advance our understanding and description of these important ecosystems, we leverage Landsat-8 and Sentinel-2 satellite data to provide a current assessment of mangrove extent within the Red Sea region and also explore the effect of spatial resolution on mapping accuracy. We establish that Sentinel-2 provides a more precise spatial record of extent and subsequently use these data together with a maximum entropy (MaxEnt) modeling approach to: i) map the distribution of Red Sea mangrove systems, and ii) identify potential areas for future afforestation. From these current and potential mangrove distribution maps, we then estimate the carbon sequestration rate for the Red Sea (as well as for each bordering country) using a meta-analysis of sequestration values surveyed from the available literature. For the mangrove classification, we obtained mapping accuracies of 98 %, with a total Red Sea mangrove extent estimated at approximately 175 km2. Based on the MaxEnt approach, which used soil physical and environmental variables to identify the key factors limiting mangrove growth and distribution, an area of nearly 410 km2 was identified for potential mangrove afforestation expansion. The factors constraining the potential distribution of mangroves were related to soil physical properties, likely reflecting the low sediment load and limited nutrient input of the Red Sea. The current rate of carbon sequestration was calculated as 1034.09 ± 180.53 Mg C yr-1, and the potential sequestration rate as 2424.49 ± 423.26 Mg C yr-1. While our results confirm the maintenance of a positive trend in mangrove growth over the last few decades, they also provide the upper bounds on above ground carbon sequestration potential for the Red Sea mangroves.
  • State of Play in Marine Soundscape Assessments

    Havlik, Michelle Nicole; Predragovic, Milica; Duarte, Carlos M. (Frontiers in Marine Science, Frontiers Media SA, 2022-06-29) [Article]
    A soundscape is the recording of all sounds present in an area, creating a holistic view of the acoustic profile in an ecosystem. Studying acoustic parameters of marine soundscapes as a whole has been shown to give an indication of the health status of the location, as well as correlate to which species may be present and using the area. With the rapid innovation of technology, especially data storage and declining cost of equipment, marine soundscape research is fast increasing, and these previous limitations have been switched for computing capacity for data analysis. Here, we perform a systematic assessment of literature of marine soundscape studies, from 1978, when the first soundscape study was reported, until 2021. We identified 200 primary research studies that recorded soundscapes and captured their geographical location, depth, habitat, duration of the study, and number of sites in each study. Using this data, we summarize the state of play in marine soundscapes studies, and identify knowledge gaps in the spatial coverage, depth profiles, habitat representation and study duration. Spatially, studies are biased towards the northern hemisphere. They are also more prevalent in more easily accessible ecosystems, in order from most to least studied, in coastal (38%), pelagic (20%), tropical coral reef (17%), rocky reef (7%), polar (5.5%), seagrass meadows, oyster reef and kelp/algal forest (4000 m. With anthropogenic noise and other pollution sources increasing globally, these gaps in research should be further addressed, especially as they pertain to vulnerable ecosystems, many of which are affected by global climate change and anthropogenic influences. It is crucial that marine soundscape studies continue to be developed and pursued, to establish baselines for healthy ecosystems and/or document recovery following management actions.
  • Acanthopagrus oconnorae , a new species of seabream (Sparidae) from the Red Sea

    Pombo-Ayora, Lucía; Peinemann, Viktor N.; Williams, Collin T.; He, Song; Lin, Yu Jia; Iwatsuki, Yukio; Bradley, Donal; Berumen, Michael L. (Journal of Fish Biology, Wiley, 2022-06-28) [Article]
    A new species of sparid fish, Acanthopagrus oconnorae, is described on the basis of 11 specimens collected in the shallow (0-1 m depth) mangrove-adjacent sandflats of Thuwal, Saudi Arabia. The new species is distinguished from its congeners by the following combination of characters: second anal-fin spine 12.8-16.6% of SL; 3½ scale rows between the fifth dorsal-fin spine and lateral line; suborbital width 5.7-6.7% of SL; eyes positioned at the anterior edge of the head, often forming a weakly convex break in an otherwise gently curved head profile, when viewed laterally; caudal fin light yellow with black posterior margin (approximately half of fin); anal fin dusky grey with posterior one-fifth of the fin light yellow; black streaks on inter-radial membranes of anal fin absent. The most similar species to Acanthopagrus oconnorae is A. vagus, which differs in having a w-shaped anterior edge of the scaled predorsal area, a more acute snout, and black streaks on the inter-radial membranes of the anal fin. The phylogenetic placement and species delimitation of A. oconnorae is discussed on the basis of COI, CytB, and 16S sequences. It is hypothesized that ecology and behavior explain how this species avoided detection despite its likely occurrence in coastal areas of the Red Sea with historically high fishing pressures.

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