An assessment of heavy metals in green sea turtle (Chelonia mydas) hatchlings from Saudi Arabia’s largest rookery, Ras Baridi

Background Anthropogenic sources can lead to the accumulation of heavy metals in marine organisms through ingestion, absorption, or inhalation. For sea turtle embryos, heavy metals can be absorbed into the egg from the incubation environment or be maternally transferred to the offspring causing neurological, reproductive, and developmental problems. Here, we report heavy metal concentrations in green turtle hatchlings from the largest rookery on the Red Sea, Ras Baridi. Methods Deceased hatchlings were collected from two beaches near a cement factory at Ras Baridi, from which heavy metal concentrations (chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb)) were measured from the liver, muscle, and residual yolk of the hatchlings. Results Although based on a small sample of hatchlings, the data presented here provides the first measurements of heavy metals from sea turtles in the Red Sea and highlights the link between human activity and its impact on the ecology of sea turtles. In general, the heavy metal concentrations of heavy metals were not significantly different between the beach next to the cement factory and the beach downwind from the factory. However, the concentrations of heavy metals were significantly different between sampled tissues (liver, muscle, and residual yolk). Discussion This study provides insight into current heavy metal levels in green turtle hatchlings, which can be used as bio-indicators for environmental contaminants as coastal development increases in the Red Sea. Moreover, we found a lack of standardized methodology to evaluate heavy metals in hatchling sea turtles. Future efforts should work toward creating comparable techniques for long-term heavy metal monitoring, as this is a useful determinant of anthropogenic pollution

Case report: tracking data from foraging hawksbill turtles in the northern Red Sea

Background: Hawksbill turtles (Eretmochelys imbricata) are Critically Endangered throughout their global range, and concerningly little is known about this species in the Red Sea. With large-scale coastal development projects underway in the northern Red Sea, it is critical to understand the movement and habitat use patterns of hawksbill turtles in this environmentally unique region, so that effective conservation strategies can be implemented. We satellite tagged three hawksbill turtles, one 63 cm curved carapace length adult male captured near Wahlei Island, one 55 cm turtle captured in the Gulf of Aqaba, and one 56 cm turtle suffering from a floating syndrome which was captured at Waqqadi Island, rehabilitated, and released at Waqqadi Island. Turtles were tracked for 156, 199, and 372 days between October 2020 and November 2021. Results: We calculated the home ranges and core use areas of hawksbill turtles using kernel-density estimations and found that each turtle showed high fidelity to their foraging sites. Home ranges calculated with GPS-derived locations ranged between 13.6 and 2.86 km2, whereas home ranges calculated with Argos-derived locations ranged from 38.98 to 286.45 km2. GPS-derived locations also revealed a higher proportion of time spent in coral and rock habitats compared to Argos, based on location overlap with the Allen Coral Reef Atlas. We also found that turtles were making shallow dives, usually remaining between 0 and 5 m. Conclusions: While the number of tracked turtles in this study was small, it represents an important contribution to the current understanding of spatial ecology among foraging hawksbill turtles globally, and provides the first-ever reported hawksbill turtle tracking data from the Red Sea. Our results suggest that protecting coral reef habitats and implementing boating speed limits near reefs could be effective conservation measures for foraging hawksbill turtles in the face of rapid coastal development

Newly described nesting sites of the green sea turtle (Chelonia mydas) and the hawksbill sea turtle (Eretmochelys imbricata) in the central Red Sea

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

A Preliminary Report of Plastic Ingestion by Hawksbill and Green Turtles in the Saudi Arabian Red Sea

(1) Background: Plastic pollution is a major environmental concern confronting marine animals. Sea turtles are considered a bio-indicator of plastic pollution, but there is little information regarding plastic ingestion by turtles in the Red Sea. With large-scale development projects being built along the Saudi Arabian coast, it is important to have a baseline for plastic ingestion before construction is complete. (2) Methods: Ten deceased sea turtles (four hawksbill and six green turtles) were collected along the Saudi Arabian coastline. Necropsies were conducted, and the entire gastrointestinal tracts were extracted and the contents were passed through a 1 mm mesh sieve. (3) Results: We found that 40% of the turtles in this study had ingested plastics. Thread-like plastics were the most common plastic category, and multi-colored was the most prevalent color category. (4) Conclusions: Monitoring of the plastic ingestion by marine megafauna should be conducted as a long-term assessment of the developments’ impacts. Additionally, conservation efforts should be focused on removing plastics (namely ghost nests and fishing lines) from the reefs and reducing the amount of plastic entering the sea

Low diversity and abundance of predatory fishes in a peripheral coral reef ecosystem

Abstract Semi‐enclosed seas are often associated with elevated local threats and distinct biogeographic patterns among marine fishes, but our understanding of how fish assemblage dynamics vary in relation to relatively small semi‐enclosed seas (e.g., the Gulf of Aqaba) remains limited. Baited remote underwater video surveys (n = 111) were conducted across ~300 km of coral reef habitats in the Gulf of Aqaba and the northern Red Sea. A total of 55 predatory fish species were detected, with less than half of all species (n = 23) observed in both basins. Relative abundance patterns between the Gulf of Aqaba and the northern Red Sea were variable among taxa, but nearly twice as many predatory fish were observed per unit of effort in the northern Red Sea. In general, assemblages in both basins were dominated by three taxa (Epinephelinae, Carangidae, and Lethrinidae). Large‐bodied and threatened species were recorded at very low abundances. Multivariate analysis revealed distinct assemblage structuring of coral reef predators between the Gulf of Aqaba and the northern Red Sea. Most of the species driving these differences were recorded in both basins, but occurred at varying levels of abundance. Environmental factors were largely unsuccessful in explaining variation in assemblage structuring. These findings indicate that biological assemblages in the Gulf of Aqaba are more distinct than previously reported and that reef fish assemblage structuring can occur even within a relatively small semi‐enclosed sea. Despite inter‐basin assemblage structuring, the overall low abundance of vulnerable fish species is suggestive of overexploitation in both the Gulf of Aqaba and the northern Red Sea of Saudi Arabia. As the region surveyed is currently undergoing large‐scale coastal development, the results presented herein aim to guide spatial management and recovery plans for these coral reef systems in relation to this development

Study area and distribution of survey effort.

Maps showing the study area (a, light green polygon) and the locations of survey effort, including: (b) aerial surveys (flight track in blue line and estimated survey swath in shaded blue polygon), (c) BRUV deployments and opportunistic sightings from vessels and snorkel, (d) SCUBA and manta tow surveys, and (e) ROV and submersible surveys. The number of surveys of each type are indicated as “n” in the top-right of each panel (for opportunistic sightings, n indicates the number of sightings). Green circles in (a) indicate restricted areas that were not accessible during surveys. The area covered by (b) is highlighted in (a) within the dashed blue rectangle. Base layer created in MapBox Studio (https://studio.mapbox.com) using freely available data from MapBox (hillshade and terrain data; can be found within the software) and Natural Earth (www.naturalearthdata.com; bathymetry and geopolitical contours).</p

Example images of marine megafauna sightings across the expedition.

Sightings including (left-to right, top to bottom): Green turtle (C. mydas), round ribbontail ray (T. meyeni), spotted guitarfish (R. punctifer), hawksbill turtle (E. imbricata), bentfin devilray (M. thurstoni), oceanic whitetip shark (C. longimanus), halavi guitarfish (G. halavi), pelagic thresher shark (A. pelagicus), and silvertip shark (C. albimarginatus).</p

Conservation status of sighted elasmobranch and Cheloniidae species.

For each main taxonomic group, conservation status is shown as percentage of encountered species that fall into each threat category (CR = critically endangered, EN = endangered, VU = vulnerable, NT = near threatened, LC = least concern, as listed on the IUCN Red List of endangered species).</p

Sightings data collected in the study and used for analysis.

Table of sightings contains species name, location record, methods of survey in which sighting was recorded, and conservation status of the species. (CSV)</p

Distribution of elasmobranch and Cheloniidae sightings.

Maps showing sightings of (a) elasmobranchs, (b) sea turtles. Sighting locations are differentiated by colour to indicate: Sharks (light blue), rays (dark blue), guitarfish (black), hawksbill turtle (light green), and green turtle (dark green). Locations where signs of nesting were recorded (abandoned nests or tracks on the shore) are indicated as red dots in (b) (the same symbol is applied for both hawksbill and green turtle nesting activity). The boundaries of the NEOM gigaproject are indicated by a red line, and areas of particular importance are highlighted in red rectangles. Base layer created in MapBox Studio (https://studio.mapbox.com) using freely available data from MapBox (hillshade and terrain data; can be found within the software) and Natural Earth (www.naturalearthdata.com; bathymetry and geopolitical contours).</p