The Al-Salam Lagoon is one of the recreational sites along the Jeddah coast, showing the environmental impacts of urbanization along the coast. A sediment core (220 cm) was collected from the intertidal zone to evaluate the heavy metals (Fe, Mn, Cr, Ni, Cu, Zn, and Pb) and geochemical indices (contamination factor, geo-accumulation index, and pollution load index). In the organ-ic-rich muddy sediments (0–100 cm), there is a high metals content and a pollution load index of ~3, indicting anthropogenic impacts with high Cu contamination (CF:12) and moderate Fe, Mn, Cr, Ni, Zn, and Pb contamination (CF: <3). The organic matter and heavy metals washed through surface run-off from the land and deposited as urban waste. Down the core, consistent metals concentration, CF, and I_geo trends indicate a common pollutant source and pollution load variations over time. In the sediment section (70–40 cm), a high organic matter, metal concentration, CF, I_geo, and PLI value (≥5) suggest an uncontrolled pollution load. The decreased and stable trends of environmental indicators toward surface sediments suggest measures taken to control the pollution along the Jeddah coast. Below 110 cm, the carbonate-rich sediments have low organic matter and metals, showing an unpolluted depositional environment. The negative geo-accumulation index implies a geogenic source and indicates no anthropogenic impacts as inferred from low (~1.0) CF and PLI.

Bottom sediments of Al-Kharrar Lagoon, Rabigh area, Saudi Arabia were analyzed for mineralogical (26 samples) and major oxides, minor, and trace elements (46 samples). The prime objective is to document the controlling factors of the mineralogical and chemical composition of the lagoon bottom sediments. Hierarchical cluster (HCA) and the principal component (PCA) analyses are used to disclose the degree of similarities among elements to distinguish them into statistically significant groups. Results clarified the interplay of terrestrial sediment influx through the temporarily active Wadi Rabigh, hydrological regime and the autochthonous biogenic sedimentation, and to a lesser extent rare anthropogenic influence that impacted the lagoon sediments. The spatial distribution of minerals shows a southward increase in the siliciclastic-related minerals (quartz, clay minerals, k-feldspars, and plagioclase along with traces of amphiboles), whereas carbonate minerals (high Mg-calcite and aragonite) dominate the northern sector of the lagoon in areas far from the influence of detrital influx. The concentrations levels of oxides, minor, and trace elements display spatial variability. Three main distinctive elemental groups were delineated appraising the analysis of the elemental interrelationships and associated statistical analysis. The first group includes the positively correlated SiO₂, TiO₂, Al₂O₃, Fe₂O₃, MnO, MgO, K₂O, Na₂O, V, Cr, Ni, Zn, Rb, and Ba, which are concentrated in the southern sector of the lagoon. The second group is the carbonate-related elements (CaO and Sr) that dominate the northern sector. The distribution patterns of P₂O₅ and Cu varied highly across the lagoon. Enrichment factors revealed moderate levels of Cu in some sites supporting the anthropogenic source. The results showed the hospitable bottom ecological status of the lagoon despite local anthropogenic stressors such as an influx of flood water that contain a mixture of lithogenic and dissolved Cu from local farming.

Twenty-nine sediment samples were collected from Hurghada Bay, a highly impacted coastal area along the Northern Red Sea of Egypt, to evaluate environmental quality and human-induced effects on benthic ostracods. As potential bioindicators, benthic ostracods are highly responsive to environmental disturbances, with pollution leading to reduced abundance, lower diversity, and increased opportunistic taxa. To investigate the link between ostracod assemblages and sediment contamination, we measured the concentrations of eight heavy metals (Cu, Cd, Zn, Pb, As, Cr, Ni, and Mn) using inductively coupled plasma–atomic emission spectrometry (ICP-AES). Multivariate statistical analyses identified three distinct ostracod assemblages distributed across three station groups with varying pollution levels. Group I, associated with offshore stations, exhibited low to moderate heavy metal (HM) concentrations and high ostracod abundance and was dominated by Moosella striata, Hiltermannicythere rubrimaris, Ruggieria danielopoli, Neonesidea schulzi, and Paranesidea fracticorallcola, where the water depth and sand content are the main controlling factors. In contrast, Group II, corresponding to stations with the highest HMs and total organic matter (TOM), was dominated by pollution-tolerant species Jugosocythereis borchersi, Cyprideis torosa, Alocopocythere reticulata, and, to a lesser extent, Ghardaglaia triebeli, with reduced ostracod density and diversity. Group III, characterized by stations influenced by the mud-controlling factor, had the lowest HMs and was dominated by pollution-sensitive species Xestoleberis rhomboidei, Paranesidea fortificata, and Loxocorniculum ghardaquensis. These findings highlight the ecological risks posed by HM pollution and emphasize the urgent need for pollution mitigation strategies and continued monitoring to preserve the Red Sea’s benthic biodiversity.

This study utilizes lithofacies characteristics, petrographic, XRD, and stable isotope data of Al-Mejarma beachrocks, Red Sea, Saudi Arabia, to interpret its depositional setting, origin of cement, and coastal evolution. The beachrock is 1.15 m thick, medium to very coarse-grained sandstone with scattered granules. It shows massive to graded bedding, horizontal, ripple, and shore parallel to slightly oblique planar cross-laminations, with a remarkable absence of bioturbation. It was deposited by shore-parallel longshore currents in a relatively high-energy beach environment. The framework comprises quartz, feldspars, and lithic fragments admixed with biogenic remains of algae, mollusca, foraminifera, corals, and echinoids. They are cemented by high magnesium calcite in the form of isopachous rims and pore-filling blades, and rarely, as a meniscus bridge. The mean values of δ¹⁸O_VPDB and δ¹³C_VPDB are 0.44‰ and 3.65‰, respectively, suggesting a seawater origin for the cement. The framework composition, facies geometry, and association with back-barrier lagoon impose a deposition as a shoreface-beach barrier through two stages corresponding to the middle and late Holocene. The first stage attests landward migrating sediment accumulation and rapid marine cementation. The sediments stored offshore during the early and middle Holocene humid periods migrated landward from offshore and alongshore by onshore waves and longshore drift during the middle and late Holocene sea-level highstand. They were cemented to form beachrock and subsequently emerged as the late Holocene sea-level fell.

Sharm El-Luli, located along the southern Red Sea coast of Egypt, is a semi-enclosed, shallow, mangrove-fringed lagoon characterized by limited hydrodynamic exchange, high salinity, and low terrigenous input. This study investigates the influence of sediment properties, hydrodynamic gradients, and mangrove-associated microhabitats on the spatial distribution of benthic ostracod assemblages within this lagoonal system. Eighteen surface sediment samples (W1–W18) were collected along an onshore–offshore gradient and analyzed for ostracod composition, sediment texture, carbonate and organic matter content, and water parameters including temperature, salinity, dissolved oxygen, pH, redox potential, and total dissolved solids. Thirty-four ostracod taxa were identified, revealing a pronounced inner–outer ecological partitioning across the lagoon. Redundancy analysis (RDA) demonstrates that ostracod distribution is primarily controlled by substrate heterogeneity, organic enrichment, salinity, and conductivity-related variables. The inner, low-energy mangrove margin is dominated by Aglaiocypris triebeli, Paranesidea fracticorallicola, and Hiltermannicythere rubrimaris, reflecting stressed, low-diversity conditions associated with organic-rich sediments and restricted circulation. In contrast, mid- and outer-lagoon stations host more diverse assemblages dominated by Xestoleberis spp., Neonesidea schulzi, Loxocorniculum ghardaquensis, and Jugosocythereis borchersi, indicative of better-flushed environments with higher carbonate content and stable marine salinity. These results demonstrate that benthic ostracods respond sensitively to fine-scale environmental gradients in mangrove-fringed lagoons, underscoring their value for assessing ecological health and sedimentary dynamics in semi-enclosed Red Sea coastal systems.

The reconstruction of detrital flux, paleoclimate, paleosalinity, paleo-primary productivity, paleohydrodynamic conditions, and paleo-water depth enhances understanding of sedimentary processes and their drivers during deep-time greenhouse-icehouse transitions, such as the Eocene–Oligocene transition. This study uses detailed geochemical analyses of major oxides and trace elements in sediment samples collected from the Beni Suef Formation (Bartonian–Priabonian) and the Maadi Formation (Priabonian) in the southern Tethys shelf (Egypt, northeastern Desert). Detrital proxies, including Si/Al, Ti/Al, and Zr/Al, indicate an enhanced influx of terrigenous sediments in the middle portion of the Qurn Member of the Beni Suef Formation, as further supported by noticeable facies variations, particularly the transition from shale to coarser silt- and sand-sized fractions. Paleoclimate indicators (Sr/Ba, Rb/Sr, K₂O/Al₂O₃, and Sr/Cu) point to a climatic shift from humid to arid conditions, consistent with the regional Late Eocene aridification across the Tethyan realm. Paleosalinity proxies (Sr/Ba, Ca/Al, and Mg/Al×100) suggest episodic intensification of open-marine influence and a reduction in freshwater input, with an upsection increase in Sr/Ba ratios, reflecting phases of enhanced marine water settings or decreased terrestrial runoff. Primary productivity was evaluated using multiple geochemical proxies, including P, Ni/Al, Cu/Al, P/Al, P/Ti, and Babio ratios. These collectively indicate generally low primary productivity interrupted by intervals of enhanced paleoproductivity or increased organic matter export to the sediments. This interpretation is further supported by the low total organic carbon (TOC) values. These results highlight the sensitivity of the southern Tethys shelf to Middle–Late Eocene climatic variability and the key role of prevailing paleoenvironmental conditions in controlling sediment supply, water chemistry, and biological productivity.