Seafloor marine litter density and distribution in the Jordanian Gulf of Aqaba, northern Red Sea.

Abstract The Gulf of Aqaba (GoA) is the seismically most active region in the Red Sea, with a history of large earthquakes and posing a high seismic hazard to coastal communities. This study uses back‐projection and dynamic rupture simulation to investigate the largest instrumentally recorded earthquake in the GoA, the 1995 7.2 Nuweiba earthquake, to understand stress loading, failure mechanisms, and cascading rupture potential on complex multi‐segment fault systems. Our results reveal a multi‐segment cascading rupture with supershear rupture on the optimally prestressed Aragonese Fault. Supershear rupture significantly amplified offshore ground shaking, elevating seismic hazard for the narrow gulf's coastal regions. This event partially ruptured the GoA fault system, increasing Coulomb stress on the unbroken southern Arnona Fault, which has been silent since 1588. This stress loading likely advanced a future rupture on this critical segment, requiring close monitoring and increased preparedness for a potential large earthquake in the region.

Marine risers are widely utilized within the offshore industry; they are often being exposed to extreme in situ structural (or environmental) dynamic loads. Robust characteristic/design values assessment for marine riser dynamics, under nonstationary ocean current actions, being a nontrivial engineering task. Vortex-Induced Vibration (VIV) may pose significant safety risks for offshore and marine energy installations. During offshore field operations, excessive loadings acting on marine risers often arise, posing operational risks. In this case study, experimental test results were utilized to analyze hydrodynamic in situ loadings acting on marine deep-sea risers, under ambient in situ environmental conditions. The current case study benchmarks a novel risk evaluation method, consisting of several critical components, that can be utilized in combination to estimate the reliability of multi-modal nonlinear dynamic systems. The first component is a dynamic system risks evaluation methodology, especially suitable for multi-modal structural (or environmental) dynamical systems, that had been experimentally measured across a representative duration, resulting in a jointly quasi-ergodic input timeseries. Another component being a novel extreme value prediction method, suitable for a wide range of engineering and industrial design applications. Multi-modal Gaidai structural risk (hazard) evaluation method yielded accurate predictions of the system’s failure (damage) risks, based on lab-measured riser dynamics. This case study aims at further benchmarking of recently developed a) state-of-the-art multidimensional reliability methodology, coupled with b) novel non-parametric deconvolution scheme, using raw experimental data as an input. It is the precise combination of these two above-mentioned methods a), b) that makes this case study of practical engineering value.

Unveiling the environmental and toxicological implications of potentially toxic elements levels in three marine fish species from the Red Sea.

Abstract Marine ecosystems, particularly in the Gulf of Aqaba, face growing threats from anthropogenic activities and industrial pollution, necessitating advanced monitoring for sustainable management. This study presents a real-time remote monitoring (RTRM) system that integrates wireless sensor networks and machine learning (ML) to enhance water quality assessment. By continuously capturing key parameters, dissolved oxygen (DO), pH, conductivity, turbidity, and sediment concentration, the system enables dynamic tracking of ecological health. Biosensors and physicochemical sensors were combined with geographic information system-based spatial analysis. At the same time, random forest and artificial neural network models were trained on 6 months of data and validated through 10-fold cross-validation, DO: RMSE = 0.45 mg/L, R 2 = 0.92. The RTRM system provided automated analytics and early warnings for environmental risks, including coral bleaching and pollutant spills. Results showed that DO levels generally supported aquatic life, though northern coastal areas were more vulnerable due to localized pollution. Turbidity and sediment patterns highlighted recreational disturbances, particularly from boating. Compared to traditional methods, the RTRM system improved predictive accuracy by 20% and reduced monitoring costs by 30%. By unifying in situ sensing, remote sensing, and ML-based forecasting, this framework offers a scalable, cost-effective tool for real-time marine ecosystem management in the Red Sea and comparable regions.

Gulf of Aqaba as a thermal refuge: Insights from four years of intensifying marine heatwaves.

Cryptic sulfur cycling, characterized by nearly quantitative oxidation of hydrogen sulfide, is characteristic for sediments with low organic matter and high reactive iron contents. A common source of reactive iron in sediments of marine systems that are located in arid environments is aeolian dry deposition of desert dust. The presence of such a cryptic sulfur cycle has previously been documented in sediments of enclosed basins such as the Red Sea and, especially, in its north-eastern extension, the Gulf of Aqaba. Here we present speciation data for iron, manganese and sulfur as well as the isotopic composition of sulfate, and demonstrate cryptic sulfur cycling in sediments from the north-east Atlantic Ocean situated in the vicinity of the Sahara. These sediments are characterized by high reactive-to-total-iron ratios and extremely low sulfur-bound iron contents. In the near-shore sediments (e.g., sediments which were sampled at < 550 km from the coast) highly reactive iron contents are higher than in the sediments, which were retrieved at higher distances from the continent. In the near-shore sediments, the most abundant highly reactive iron fraction is dithionite-extractable iron, which comprises goethite, hematite, and akaganéite. This is the most abundant group of minerals in the Saharan dust collected above the Red Sea. On the other hand, contents and speciation of highly reactive iron does not significantly affect sedimentary sulfur-bound iron contents. We suggest that cryptic sulfur cycling is a common phenomenon for sediments in the ocean situated near arid environments.

Microphytoplankton community structure in the Gulf of Aqaba and northern Red Sea

Octocorals, a globally distributed class of Cnidaria, inhabit a wide range of environments, from cold to tropical waters and from shallow to deep-sea ecosystems. In the Red Sea, studies on octocoral diversity have mostly been focused on the Gulf of Aqaba and selected families or genera. While these studies have revealed a remarkable richness and diversity of shallow-water species, mesophotic and deep-sea octocoral research remains limited in the region, in particular along the Saudi Arabian coast. Here, we provide a first comprehensive assessment of this group's genetic diversity across the basin's bathymetric and latitudinal gradients. Following six Red Sea oceanographic expeditions and various biodiversity surveys conducted between 2020 to 2023, we analysed a collection of 728 octocoral specimens sampled along 13 degrees of latitude in the Saudi Arabian Red Sea, from shallow-water reefs to deep-sea habitats. We combined morphological identification and sequencing of mitochondrial barcode markers (mtMutS and COI) to delimit lineages. Our integrated results revealed the occurrence of 26 families and 56 genera in the basin from 3 to 859 m of depth. While the description of new species was beyond the scope of this work, here we provide a reference dataset for octocoral diversity from a biodiversity hotspot, as well as essential insights to inform biodiversity management and planning of conservation measures, particularly relevant for the rapidly developing Saudi Arabian Red Sea coast.

ABSTRACT Marine environment is increasingly impacted by anthropogenic pollution, especially Potentially Toxic Elements (PTEs) that accumulate in sediments and threaten marine ecosystems. This study compares PTE concentrations in coastal sediments from Lebanon (Mediterranean Sea) and Jordan (Red Sea), revealing distinct regional patterns. Sediment samples were collected along both coastlines, and 10 toxic elements (Al, As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) were analysed using ICP-MS. PCA and HCA identified aluminium and chromium as key in sediment classification, linked to industrial and port activity. In Lebanon, Jounieh had high levels of Al, Mn, Cd, Ni, As, Cu, and Co, with Al levels similar in Jounieh and Akkar (1170.31 and 1185.83 ppm). As a crustal element, Al originates from terrestrial sources. Damour and Jounieh also had elevated Mn (67.34 and 67.43 ppm), known for its aquatic mobility. Cr peaked in Nahr Ibrahim (93.1 ppm), followed by Jounieh (90.9 ppm). In Jordan, the Visitor Center had the highest concentrations of most elements, including Al (998.41 ppm), As, Cd, Co, Cr, Cu, Mn, and Ni. Zn was also high in busy areas like the Hotel Area and Oil Terminal Port. The Marine Science Station has the highest Pb (2.18 ppm) but low levels of other elements. The Hotel Area ranked second for Al and Pb and was among the top for other metals. Contamination factor analysis supported PCA and HCA results, showing higher contamination at Lebanese sites and lower in the Gulf of Aqaba. Al and Cr were the main drivers of site grouping, while other elements had low impact (contamination factor < 1). These results highlight the greater environmental vulnerability of not only Jordan and Lebanon but also the countries that have coastline on the Mediterranean and Red Sea and the need for targeted monitoring and management from the local and international communities.

Abstract This study presents an advanced real-time monitoring system integrating wireless sensor networks with machine learning to assess water quality in the Gulf of Aqaba. Our hybrid machine learning framework combines Random Forest (500 trees, node size = 5) for feature selection with Artificial Neural Network ensembles (3-layer MLP with Monte Carlo dropout) for probabilistic forecasting. The system continuously monitors six critical parameters, demonstrating strong predictive performance through rigorous validation: dissolved oxygen (R² = 0.92, RMSE = 0.45 mg/L, 95 % CI (Confidence interval): 0.41 - 0.49), nitrite (R² = 0.85, RMSE = 0.08 mg/L, CI: 0.07 - 0.09), and turbidity (R² = 0.89, RMSE = 2.3 FTU, CI: 2.1 - 2.5). Comprehensive uncertainty analysis revealed prediction intervals of ±0.38 mg/L for DO and ±0.10 mg/L for nitrite, with spatial variability lowest in open waters (CV = 8.2 %) and highest near coastal zones (CV = 15 %). Residual autocorrelation analysis confirmed model reliability (Moran’s I &lt; 0.12, p &gt; 0.05) across the study area. Spatial-temporal analysis identified nitrite as a sensitive pollution indicator, with concentrations reaching 0.12 mg/L near urban outflows compared to background levels (&lt; 0.05 mg/L). The system achieved 92 % accuracy in the early detection of environmental risks, including coral bleaching precursors (temperature anomalies &gt; 1 °C) and pollution events (nitrite spikes &gt; 0.1 mg/L). Compared to conventional monitoring, the platform demonstrated 20.4 % greater predictive accuracy (ΔR² = +0.17, p &lt; 0.01) while reducing operational costs by 30.2 %, primarily through automated data collection and reduced manual sampling. The integration of high-frequency sensing, adaptive machine learning, and cloud-based analytics establishes a replicable framework for coastal ecosystem management, particularly in anthropogenically stressed environments like the Red Sea.

This study focuses on the levels of heavy metals (HMCs) in the commonly consumed marine fish from the Aqaba Gulf, Red Sea, Egypt. It evaluates the effectiveness of soaking treatments as a novel approach to reducing HMCs. The order of metals varied among species, with sigan and bongos fish following Mn < Ni < Cu < B < Fe < Zn, while mallas fish followed Mn < Ni < Cu < Zn < Fe < B. The highest level in untreated samples was observed in sigan for Zn (67.60 ± 2.34 µg/g ww-b), while the lowest was recorded in bongos for Mn (0.96 ± 0.07 µg/g ww-b). Soaking treatments significantly reduced HMCs in all species, as confirmed by environmental risk indices. Risk assessments revealed that the hazard index (HI-HMCs) values for children often exceeded the acceptable threshold of HI-HMCs ≤ 1, suggesting potential health risks despite reductions achieved through soaking. Among the soaking methods, the mixed soaked treatment, which combined salt and apple vinegar, showed the most pronounced reduction in metal levels, demonstrating a synergistic effect. In conclusion, while soaking treatments effectively mitigate HMCs contamination, further efforts are required to develop safer fish processing methods, particularly to safeguard vulnerable groups like children.

Marine sponges are known for their rich variety of secondary metabolites, many of which show potential for pharmaceutical applications. In this study, three deep-sea sponge species—Stelletta fibrosa, Dactylospongia elegans, and Haliclona manglaris—were identified using DNA barcoding, and their ethanolic extracts were tested for antibacterial activity. The extracts were evaluated against Gram-positive (e.g., Bacillus pumilus, Staphylococcus aureus, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus, MRSA) and Gram-negative bacteria (e.g., Escherichia coli and Klebsiella aerogenes) using the agar well diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined. Among the extracts, D. elegans exhibited the most potent antibacterial activity, with inhibition zones ranging from six to 21 mm against gram-positive bacteria and low MIC/MBC values from 0.25 to three mg/ml. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis of D. elegans revealed the presence of bioactive compounds such as gallic acid, caffeic acid, bolinaquinone, dactyloquinone, and others, which are known for their antimicrobial properties. These findings suggest that D. elegans has promising antibacterial properties that could be valuable in combating antimicrobial resistance.

ABSTRACTProtists are major functional players in the oceans. Time‐resolved protist diversity and succession patterns remain poorly described in subtropical ecosystems, limiting current understanding of food web dynamics and responses to environmental changes in these major world‐ocean regions. We used amplicon sequencing data and trait‐based annotation to examine the seasonality of planktonic protists in the subtropical Gulf of Aqaba (Red Sea). Temperature and nutrients were the major drivers of succession. We detected marked seasonal shifts in protists. Heterotrophs, including diverse parasitic functional groups, dominated the warm, stratified oligotrophic period spanning spring and summer. By contrast, nutrient influx during deep convective mixing in winter triggered a shift to photoautotrophic communities dominated by a few genera of chlorophytes. Deeper winter mixing resulted in larger blooms at the onset of stratification dominated by diatoms, relative to chlorophytes that prevailed during shallower blooms. This result illustrates the impact of mixing depth on bloom formation and composition. Comparisons with oceanwide rDNA datasets indicate that the oligotrophic protist assemblages from the Gulf resemble those from warm, open oceans. This work provides a detailed assessment of the seasonal switch in dominant trophic functions in protists in phase with nutrient levels in a subtropical planktonic ecosystem.

Structure and complexity of a rariphotic coral ecosystem in the Gulf of Aqaba (Red Sea)

Response of seaweed associated microbiome to environmental disturbances from the Gulf of Aqaba, Jordan

Abstract This study provides a comprehensive assessment of environmental and human health risks associated with potentially toxic elements in the coastal sediments of the Gulf of Aqaba. A total of 33 sediment samples were analyzed using inductively coupled plasma mass spectrometry, revealing Fe (1,526–5,123 mg/kg), Zn (16.8–32.0 mg/kg), Pb (3.5–9.1 mg/kg), Co (2.2–6.4 mg/kg), and Cd (0.05–0.18 mg/kg). The concentrations detected were within acceptable limits and below the Interim Sediment Quality Guidelines, indicating minimal environmental risk. Environmental indices, including the pollution index, modified contamination degree, pollution load index, hazard index, and lifetime cancer risk indicate no contamination or health risks for adults or children through ingestion and dermal contact pathways. Principal component and correlation analysis suggest that Fe, Zn, and Co primarily originate from natural geological processes due to their strong association with elements typically derived from bedrock weathering, while minor anthropogenic contributions may arise from tourism and coastal activities. The findings confirm that the sediments pose no environmental or health risks, providing a baseline for future monitoring and pollution management in the Gulf of Aqaba.

The coral genus Madracis has a global distribution from shallow waters to over 1200 m depth. In the Red Sea, the azooxanthellate endemic species Madracis interjecta is known to occur from depths of 120 to 350 m. This species is often observed in mesophotic ecosystems and has been reported to form sediment-binding bioherms, yet the conditions required for these formations are not understood. Here, we extracted quantitative data from video footage to identify the distribution of M. interjecta for the first time along the Saudi Arabian Red Sea coast. We present a habitat suitability model to identify potential habitats in the northern Red Sea and Gulf of Aqaba for this species. Combining presence data with geomorphometric variables and environmental data, we identified both depth and seafloor ruggedness as main drivers of this species distribution. Through multivariate statistics, we found that bioherms were found in deeper and cooler waters than individual M. interjecta colonies. Due to the narrow continental shelf and steep slopes of the northern Red Sea and Gulf of Aqaba, the effects of coastal development are threatening shallow, mesophotic and deep ecosystems. This work provides both a baseline survey and predicted distributions of an important habitat-forming scleractinian coral, which can inform conservation planning in the region.

Coral reefs are biodiversity hotspots, where new species continue to be discovered. Stylophora pistillata, a depth-generalist coral, is widely distributed throughout the Indo-Pacific and has long been considered the poster child for phenotypic plasticity. It occupies a wide range of reef habitats and exhibits a myriad of gross morphologies. Here, we used reduced representation genome sequencing (nextRAD) to assess the genetic structure of adults and recruits of S. pistillata across shallow and mesophotic populations in the northern Red Sea (Gulf of Aqaba). Across analytical approaches, we observed a complex genetic structure with at least four genetically divergent lineages occurring sympatrically with little to no admixture and structured by depth. Morphological and physiological differences previously documented suggest that the long-considered ecological opportunism of S. pistillata in the Red Sea may, in fact, have a genetic basis. Assessment of both adult colonies and recruits within each of the lineages also revealed the prevalence of local recruitment and genetic structuring across the eight-kilometer section of the Israeli Red Sea coastline. Overall, the observed patterns confirm the presence of undescribed diversity within this model organism for coral physiology and corroborate a broader pattern of extensive undescribed diversity within scleractinian corals.

Abstract Source-to-sink studies commonly assume independent sediment routing systems for siliciclastics and carbonates. This study integrates satellite-derived topography, imagery, swath multibeam bathymetry, and field observations to characterize a mixed carbonate-siliciclastic routing system from source to sink in the Gulf of Aqaba, northern Red Sea. The study area is lined by ephemeral desert streams (wadis) that deliver pulses of sediment to the shelf and basin during flash floods. We find that where wadis are distributary at the coast, they deposit amalgamated fan deltas associated with a continuous fringing reef, a narrow continental shelf, and a smooth line-fed slope system devoid of major submarine canyons or fans. Where knickpoints have migrated to the shoreline or into active wadi channels, the fringing reef is bisected by reentrants (sharms), there is no continental shelf, and the slope is composed of a rugged assortment of canyons and ridges. Development of sharms is the net effect of erosion by headward knickpoint migration and construction by differential aggradation on the shelf. Submarine fans linked to shelf-incising canyons are generally larger than those associated with slope-confined canyons. Fan size strongly correlates with the catchment area of the affiliated wadi networks, linking terrigenous and marine sedimentary systems. Our study offers a window into coupled terrigenous, coastal, shelf, slope, and basinal processes that have produced a steep, narrow, mixed carbonate-siliciclastic margin. The findings presented herein build on traditional depositional models and demonstrate feedbacks between integrated carbonate and siliciclastic sediment routing systems, especially in an arid climate.