Green Turtle Population Research Articles

Recommendation of consensus definition of sea turtle fibropapillomatosis

AbstractSea turtle fibropapillomatosis (FP) is an emerging transboundary contagious disease that affected concomitantly two different marine hot spots in the Northern Atlantic Ocean and in the South China Sea at the beginning of the twentieth century. FP reached a panzootic status in the 1990s in green turtle (Chelonia mydas) populations, with increased risks of emergence and spread of the disease which have been correlated with climate induced terrestrial and oceanic physical and chemical changes. During 2023–2024, scientific experts performed a bibliographic review and recommend the consensus definition of sea turtle fibropapillomatosis. FP is an emerging transboundary viral terrestrial and aquatic contagious neoplastic syndrome involving cancerous molecular transmission pathways, which may affect all species of sea turtles at all life stages. The diagnosis of the most common verrucous form of FP is pathognomonic by visual examination of a sea turtle. We summarize the main clinical characteristics of FP, moderated by a degree of confidence of research findings adapted from the Intergovernmental Panel on Climate Change (IPCC) assessment reports. We recommend the implementation of a universal and transparent monitoring strategy of sea turtle fibropapillomatosis in sentinel bays, under the governance of the World Organisation for Animal Health.

High thermal tolerance of egg clutches and potential adaptive capacity in green turtles

Climate warming threatens sea turtles, among other effects, because high temperatures increase embryo mortality. However, not all species and populations are expected to respond the same way because they could have different thermal tolerances and capacities to adapt. We tested the effect of incubation temperature on egg mortality in a population of green turtles (Chelonia mydas) previously suggested to be less affected by extreme climatic events than others. We (1) assessed the relationship between temperature and hatching success, (2) defined an optimal range of temperatures that maximized hatching success and (3) assessed the variability in the response to temperature among clutches laid by different mothers, which could allow adaptation. Hatching success was consistently high in green turtle clutches with a skew toward high values, with 50 % of clutches having a success above 94 %. Yet, it was mildly affected by temperature, declining at both low and high temperatures. The optimal range of mean incubation temperatures was between ~30.5 °C and 32.5 °C. Current mean temperatures (31.3 °C) fall within the middle of the optimal range, indicating a potential resilience to further rises in mean nest temperature. Hatching success was best described by nest temperature and the interaction between female identity and temperature. This last predictor indicated a variability in thermal tolerance among clutches laid by different mothers and therefore, a capacity to adapt. The studied population of green turtles seems to be less vulnerable than others to climate warming. Understanding how different populations could respond to increasing temperatures could help complete the picture on the potential effects of climate change on sea turtles.

Abundance, production, and migrations of nesting green turtles at Rose Atoll, American Samoa, a regionally important rookery in the Central South Pacific Ocean

Sea turtles are a taxon of conservation concern and are highly migratory, exposing them to a variety of threats (e.g., fisheries bycatch, direct harvest) across their lifetime. Understanding the abundance of nesting females, hatchling production, and migratory movements - three of the most basic biological data needs for this species group - is imperative for population assessment. This study summarizes novel data most relevant to population assessments of the endangered central south Pacific (CSP) green turtle (Chelonia mydas) population, determined from annual rapid assessment surveys (mean survey duration=7.6 days year-1, n=61 survey days over 8 nesting seasons) and satellite telemetry at Rose Atoll, American Samoa, from 2012 to 2019. A minimum of 138 unique females nested in the Rose Atoll National Wildlife Refuge (RANWR) over the study period with 218 total females observed. Satellite tracks of post-nesting females suggest Fiji (n=33/48, 70.2%) is the primary foraging ground for turtles nesting at RANWR, though other areas throughout the south Pacific Ocean are also important. Limited data suggest hatchling production was high (average hatching success=92.3%) and nest temperature data collected from 2017-2019 suggest primary sex ratios were likely balanced during this time. These are positive signs for the resilience of this nesting population, but climate change poses threats to RANWR and other low-lying tropical islands throughout the central south Pacific, as nesting areas are potentially exposed to beach erosion, tidal inundations, and increasing temperatures leading to sex bias and embryonic death.

Enhancing green sea turtle (Chelonia mydas) conservation for tourists at Little Liuqiu island, Taiwan: Application of deep learning algorithms

Observing marine life has emerged as a pivotal catalyst for the growth of the Blue Economy. Yet, overzealous and recurrent observations may exert undue stress on marine creatures, thereby complicating the sustainable management of marine assets. After the easing of Covid-19 pandemic restrictions, a notable influx of tourists to Little Liuqiu Island, Taiwan puts considerable stress on its green sea turtle population. This surge intensified incidents of illegal harassment, triggering concerns from both the local community and administrative bodies. The prevailing challenge is to ensure tourists observe these turtles with respect, refraining from behaviors such as touching or pursuing them. Addressing this, our study harnesses deep learning algorithms to equip ecotourism operators and tourists with tools to detect green sea turtles across diverse coastal terrains, reinforcing conservation efforts. Our analysis scrutinized object detection AI models, namely YOLOv3, YOLOv5s, and YOLOv5l. Fieldwork was undertaken on the island to gather ample training images, capturing elusive green sea turtles in various settings, from coastline strolls to drone imagery. Supplemental images sourced from local social media platforms were later added. Contrary to expectations, we found that merely expanding the training dataset did not guarantee improved outcomes. Instead, the variance in image content, considering distances, angles, and turtle appearances, played a pivotal role in enhancing model precision. Through our experimentation, the streamlined YOLOv5s model consistently eclipsed its more complex counterparts in performance. An AI service, underpinned by the YOLOv5s model, has been launched to distinguish between green sea turtle types for tourist-focused conservation initiatives. Future iterations will incorporate user feedback to refine accuracy. Our research breaks new ground, spotlighting the intricacies of gathering natural environment data, pinpointing optimal AI models, and evaluating their practical implications for green sea turtle conservation.

The foraging ecology of green turtles (Chelonia mydas) in New Caledonia

Green sea turtles (Chelonia mydas) face many threats from anthropogenic activity and are listed as Endangered on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. They spend the majority of their lives in coastal foraging areas, and show strong fidelity to narrow foraging ranges. Understanding the foraging ecology of green turtles is therefore important for their management and conservation. Using stable isotopes analysis (n = 200) and identification of stomach contents (n = 21), this study investigated the foraging ecology of four distinct green turtle foraging aggregations (Goro, Isle of Pines, Ouen Island and Uo/Mato Islands) within the Grand Lagon Sud. This World Heritage Area located in New Caledonia supports regionally important nesting and foraging green turtle populations. The δ13C and δ15N values of skin samples ranged from − 19.3 to − 7.3‰ and 2.8–15.9‰, respectively. Metrics of isotopic niche and regression analyses were used to assess the degree of omnivory, trophic diversity and potential ontogenetic diet shifts in the different aggregations of foraging green turtles in this location. Each of the four sites and four age-classes had distinct isotopic niches, with evidence of omnivory and ontogenetic shifts, particular in new recruits and juveniles, and at Goro and Uo/Mato Islands. This was generally supported by the stomach contents analyses of a small number of green turtles opportunistically sampled from traditional ceremonies. This study provides important information on the foraging ecology of green turtles in New Caledonia, supporting management outcomes in this region. This collaboration with the tribes of the Grand Lagon Sud is also the first step towards the integrated management of the resource.

The success rate of hatching green turtles with semi-natural incubation systems in the marine rides of Paloh district

Paloh Beach, Sambas Regency is the most potential beach as a green turtle nesting (Chelonia mydas) and is the longest turtle nesting site in Indonesia. The sustainability of green turtles is still an issue that must be resolved. Many factors influence such as extreme climate change, predator disturbance, and human actions so that the green turtle population is declining and even threatened with extinction. The purpose of this study was to determine the success rate of hatching green turtles with semi-natural incubation systems in Paloh District. The location and time of the research were carried out at Wahana Bahari Paloh domiciled in Setinggak Hamlet, Sebubus Village, Paloh District, Sambas Regency, West Kalimantan for 4 months from February to June 2023. The method used is the descriptive method. This research activity includes transferring turtle eggs to semi-natural nests (egg relocation), demolition of semi-natural nests, and calculating the hatchability rate of green turtle eggs. The result of this study is that the success rate of hatchability of green turtle eggs on average is 78.70%

Genetic structure and diversity of green turtle (Chelonia mydas) in the Gulf of Thailand.

The International Union for the Conservation of Nature and Natural Resources lists the green turtle as endangered. Green turtle nesting behavior in the Gulf of Thailand has decreased to <50% of the 1995 level. The population structure of green turtles in the Gulf of Thailand has not yet been studied. This study aimed to characterize the genetic diversity of green turtles in the Gulf of Thailand based on comparisons of mitochondrial DNA (mtDNA) control region with sequences of Indo-Pacific management units (MUs) and rookeries, to investigate population structures, and to explore phylogeographic relationships. Blood samples (1 mL each) from 91 stranded green turtles were collected from four parts of the Gulf of Thailand (eastern, upper, central, and lower). The control mtDNA region was amplified by polymerase chain reaction using LCM15382 and H950 primer. The obtained 384-bp or 770-bp sequences were analyzed for haplotype, clade, and haplotype and nucleotide diversities and were used to construct a phylogenetic tree and haplotype network diagram, respectively. In addition, we analyzed genetic differentiation within and among populations of green turtles in the Gulf of Thailand and between green turtles in the Gulf of Thailand and other Indo-Pacific MUs and rookeries. In total, 12 (based on 384 bp) or 13 (based on 770 bp) haplotypes and two clades (clades VII and VIII) were identified, with nine or 10 haplotypes belonging to clade VIII and three haplotypes belonging to clade VII. Of the new haplotypes, four or five were identified and classified as clade VII (two haplotypes, for both fragment lengths) and clade VIII (two or three haplotypes, for 384 bp or 770 bp fragments, respectively). The overall haplotype and nucleotide diversity of green turtles in the Gulf of Thailand were high (0.755 ± 0.039 and 0.01146 ± 0.00248, respectively). Based on the analysis of molecular variance, green turtles in the Gulf of Thailand could be divided into two subpopulations (UC-Eastern Gulf of Thailand [UC-EGT] and lower Gulf of Thailand [LGT]). Comparisons with other MUs and rookeries in the Indo-Pacific showed that UC-EGT was not genetically different from the Peninsular Malaysia and Eastern Taiwan (Lanyu) MUs and the Terrangganu and Mersing rookeries, and LGT were not genetically different from Peninsular Malaysia, Sipadan, Brunei Bay, Eastern Taiwan (Lanyu), Scott Reef and Browse Island, and Gulf of Carpentaria MUs and the Perak, Perhentain Island, Redang, Pahang, and Vietnam rookeries. To the best of our knowledge, this is the first report to identify the haplotypes and clades of green turtles in the Gulf of Thailand and to show that the populations in the Gulf of Thailand not only present high genetic diversity but also have haplotypic endemism. Longer mtDNA fragments (770 bp) increased the resolution of the stock structure. Clade VII is a unique clade not only for Japan but also for Thailand and Malaysia, and CmP82 is a unique haplotype for both the Gulf of Thailand and Malaysia. Conservation and management of these populations are important to preserve the genetic diversity, biological diversity, and evolutionary potential of green turtles in the Gulf of Thailand.

Using ISSR markers to detect genetic variation for marine turtles populations in Egypt loggerhead (Caretta caretta) and green turtles (Chelonia mydas)

In Egypt, along the Mediterranean coast, the loggerhead (Caretta caretta) and green (Chelonia mydas) come during nesting season to lay their eggs or for food with a rare occurrence for the leatherback turtle (Dermochelys coriacea). In the Egyptian Red Sea there are five species that come to visit, the most common to observe are hawksbill (Eretmochelys imbricata) and green (Chelonia mydas). The goal of this study is to conduct some genetic and ecological analyses a) to generate new markers that include other segments of marine turtles’ genome, as a tool to investigate new areas of variation/polymorphism between, among, and within populations and individuals; b) determine genetic diversity between and within the Mediterranean and the Red Sea populations using (individuals from the same and different habitats using ISSR); and c) determine allele frequency. At the ecological level, this study aims to assess sea turtles' habitat and population distribution among different habitats in Egypt. Throughout the duration of this study, it was noted that there was a decrease in nesting areas attributable to the loss and fragmentation of habitats. Although there are some areas with no significant nesting prosperities it considered significant areas for foraging and highly important as migratory corridors, especially in the Mediterranean. The massive urbanization and unplanned touristic developments affect sea turtle habitat over the Egyptian Mediterranean coast. The Mediterranean coast showed demographic changes in the coastal regions. On the other hand, areas could still be valued with significant nesting areas for sea turtles, but an intense and regular monitoring programme should be established. The Red Sea needs a regular monitoring programme for better management conservation measures to be adopted. The polymorphism percentage resulting from ISSR marker was 45 and 36 for both loggerhead and green turtle populations in the Mediterranean, respectively; and 69 for the green turtle populations in the Red Sea.

The Ongoing Battle: Understanding the Population Trends of Green Turtles in Peninsular Malaysia

Sea turtles are crucial marine animals. They act as indicator to a healthy marine ecosystem. However, they are subjected to different challenges and threats which results of their declining population. This study looks at the population trends of sea turtles in Malaysia by examining the numbers of nests, eggs, and hatchlings in six states in Peninsular Malaysia which are Perak, Pahang, Melaka, Johor, Terengganu, and Negeri Sembilan. Statistical distribution, hatching success percentage, trend landing and hatching, and linear regression analysis are implemented. The results show that Terengganu, on the east coast, consistently has the highest numbers of nests, eggs, and hatchlings, highlighting its key role in sea turtle conservation. In contrast, Melaka has the lowest numbers, pointing where conservation efforts could be increased. This study provides valuable insights into the differences in green turtle populations across states and identifies critical areas for focused conservation strategies to better protect and help these endangered species recover in Malaysia.

Trophic history of Hawaiian green turtles as revealed by stable isotope ratios (δ13C, δ15N and δ34S) in the bones of museum specimens

Abstract Understanding consumer trophic status and long‐term dietary changes can yield information about impacts of altered habitats on their ecology. In Hawai'i, coastal ecosystems have been significantly modified by the introduction of invasive seaweeds and mangroves, high nutrient load and overfishing, but so far, much is still to be understood about how these changes have affected the green turtle (Chelonia mydas). This study analyzed stable carbon, nitrogen, and sulfur isotope ratios in the bone tissue of modern and museum specimens of green turtles collected from 1901 to 2020 in Oahu and the North‐western Hawaiian Islands to understand how their isotopic niche has changed through time, a crucial step towards restoring the ecological role of a formerly decimated species. The standard ellipse size and the total area of the convex hull of the isotopic niche of green turtles in three periods (1901–1951, 1992–2008, and 2018–2020) were calculated. The stable isotope values of ancient green turtles (1901–1951) suggest that they relied heavily on macroalgae even before the introduction of exotic species and eutrophication promoted the development of algal pastures. However, a few ancient green turtles relied heavily on seagrasses, and others complemented their macroalgae‐based diets with significant amounts of animal matter. Such diet specialists were missing from the sample of current green sea turtles, suggesting that these foraging strategies are less common or perhaps even absent in the current population. The results suggest that green turtles have converged on the use of the most abundant resource, red macroalgae, likely because of the homogenization and simplification of coastal habitats and food webs due to anthropogenic influences. Restoring the population size of herbivorous fishes and a more diverse ecosystem structure may be necessary to recover the array of trophic strategies formerly present in the Hawaiian green turtle population.

New nesting site for the expanding green, olive ridley and hawksbill turtle populations in Cabo Verde

Currently, some sea turtle populations are expanding their home range distribution toward higher latitudes at an unprecedented rate. These expansions are associated to factors such as climate change or and increased conservation efforts. Already home to one of the largest loggerhead turtle (Caretta caretta) rookeries in the world, the islands of Cabo Verde Archipelago have recorded sporadic nesting of green (Chelonia mydas), olive ridley (Lepidochelys olivacea) and hawksbill (Eretmochelys imbricata) turtles in recent years. Here, we present the compiled information on these sporadic nesting events that occurred between 2013 and 2022 and discuss possible causes for their occurrence. Throughout the study period, the green turtle was documented on 20 occasions, the olive ridley on 25 occasions and the hawksbill on three occasions. All nesting females were found untagged and were subsequently tagged. Nesting activities occurred on the islands of Santo Antão, Sal, Boa Vista and Maio, most of them within the Sea Turtle Natural Reserve in Boa Vista Island. We suggest introducing new conservation strategies targeting the green, olive ridley, and hawksbill turtles nesting in Cabo Verde. We further suggest the use of genetic studies to determine the population origins of these three species.

Regional differences in Hg contents in the liver and muscle of the green turtle (Chelonia mydas) from three foraging grounds in Northeast Brazil.

Mercury (Hg) is a highly toxic pollutant that endangers several marine animals, including green sea turtles (Chelonia mydas), particularly in their foraging grounds along Brazilian coastal waters. Environmental Hg levels differ along this extensive littoral, rendering mandatory Hg long-term assessments of the different Hg fate in different sectors of the Brazilian coast. This study quantifies total Hg concentrations in the liver and muscle of green sea turtle populations from three foraging coastal regions in northeastern Brazil and analyzes Hg concentration differences given the locality and size of 61 juvenile individuals sampled. The results showed wide variations in Hg concentrations in the liver (81-3135 ng g-1) and muscle (10.1-8569 ng g-1). There was no significant correlation between animal size and Hg concentrations. Also, no difference was found among areas, reflecting the opportunistic feeding habit of juveniles of this species. This suggests that, in the case of green turtles, the ontogenetic change of diet plays an important role in influencing Hg concentrations found in this species.

Sustainable mindsets: Combining traditional indigenous knowledge with non-aboriginal understanding to address environmental risks

Aboriginal and Torres Strait Islander peoples are the traditional owners of Australia. It has been predicted that they have been the custodians of these lands for at least 60,000 years. Their traditional lands are inextricably linked to their languages, cultural practices and spiritual being. As the custodians they have used their traditional Indigenous knowledge to care for the land – its plants, animals and waterways, protecting unique ecosystems and maintaining sustainability. In fact, their traditional understanding reflects what has been described in the literature as a sustainable mindset. We come together as non-Aboriginal and Aboriginal educators to explore how environmental threats within the epoc of Anthropocene may be addressed using such a sustainable mindset – one reflecting both indigeneity and posthumanism perspectives. We describe three case studies showing how the use of traditional knowledge held by local Indigenous communities (IPLCs) can be used with non-Indigenous knowledge to address human induced planetary changes to protect important animal species and the land on which they live. We draw on written and oral reports from our Indigenous co-authors and data obtained informally from them by way of ‘yarning’. We describe how in the north-west of Western Australia areas of significant ecological and cultural value are being negatively affected by human-induced change threatening different animal species and ecosystems. We outline the effects of light pollution in Port Hedland and how this is disrupting the life cycle of the flatback sea turtle - culturally significant sea animals. As a point of comparison, we next describe how green back turtle and Dugong populations are being protected and sustained on the Dampier Peninsula using traditional knowledge more recently supplemented through the work of the Bardi Jawi Rangers. Finally, we examine how the Fitzroy River catchment area is increasingly under threat from water extraction and mining, but how a sustainable mindset can be used to obviate these environmental risks.

Health status and genetic compositions of green turtles (Chelonia mydas) foraging in Brunei Bay.

Long-term monitoring of sea turtle aggregations is critical for understanding the impacts of environmental changes on their population health and habitat suitability. Brunei Bay is a significant foraging ground for green turtles in the South China Sea. We analyzed the body size, hematology and body condition of green turtles for their health status in their foraging ground in Brunei Bay over a period of nine years (2011-2019). Additionally, we used mitochondrial DNA (mtDNA) to evaluate changes in the size and genetic composition of green turtle aggregations. Our findings revealed that the size composition of the green turtle population varied seasonally, but there were no significant temporal changes in genetic and size compositions. Hematology parameters and Fulton's body condition index were consistent with those reported for apparently healthy green turtles. Furthermore, we found that blood reference intervals indicated the turtles were healthy. These results provide valuable baseline data for future comparisons with other foraging aggregations and for long-term monitoring of green turtles in Brunei Bay.

Forty years of monitoring increasing sea turtle relative abundance in the Gulf of Mexico

Longitudinal data sets for population abundance are essential for studies of imperiled organisms with long life spans or migratory movements, such as marine turtles. Population status trends are crucial for conservation managers to assess recovery effectiveness. A direct assessment of population growth is the enumeration of nesting numbers and quantifying nesting attempts (successful nests/unsuccessful attempts) and emergence success (number of hatchlings leaving the nest) because of the substantial annual variations due to nest placement, predation, and storm activity. We documented over 133,000 sea turtle crawls for 50.9 km of Florida Gulf of Mexico coastline from 1982 to 2021 for a large loggerhead turtle nesting aggregation and a recovering remnant population of green sea turtles. Over time both species have emerged to nest significantly earlier in the year and green sea turtle nesting seasons have extended. Nest counts and hatchling production for both species have significantly increased, but the rate of emergence success of hatchlings leaving nests has not changed for loggerheads and has declined for green sea turtles. Sea level rise and coastal developments undoubtedly influence coastal habitats in the long-term, impacting nest site selection and potential recruitment from the loss of emerged hatchlings. However, the present indications for steady Gulf of Mexico recovery of loggerhead and green sea turtles counter findings of the Florida Atlantic coasts. This study indicates that effective conservation practices can be detected within time scales of 1–2 turtle generations.

Population genetic structure and mixed stock analysis of the green sea turtle, Chelonia mydas, reveal reproductive isolation in French Polynesia

The green turtle, Chelonia mydas, is a migratory marine species with a circumglobal distribution in tropical and temperate waters. Its natal homing behavior leads to a complex genetic structure with genetically differentiated populations that breed separately and mix within the same foraging grounds. Delineating the boundaries of these populations and their connectivity to feeding grounds is important for the management of this species, classified as endangered on the IUCN red list. Here, we examined the genetic structure and the origin of the green turtle in French Polynesia with 239 samples collected during nesting or hatchling events and 204 samples collected outside of nesting events, across 21 islands. Amplification of the 770pb mtDNA control region fragment, the standard base used to characterize haplotype diversity in this species, revealed 23 haplotypes including three novel ones, belonging to 6 different lineages. Haplotype diversity in the rookeries was 0.615, and nucleotide diversity was 0.019, values similar to those in the North West Pacific and Western Indian Oceans, two regions recognized as genetic diversity hotspots for C. mydas. The genetic structure between the Leeward and Windward Islands of the Society archipelago was found to be significant with pairwise Fst index and φst distance. Island groups (Windward Islands, Leeward Islands, Tuamotu) were genetically different from all other identified Pacific management units, with a weak differentiation between American Samoa and Leeward Islands. A mixed-stock analysis for the French Polynesian mixture revealed an exclusive contribution from the French Polynesian rookeries, with negligible input from the other Pacific populations. This study provides the first assessment of the genetic structure of green turtle populations within French Polynesia and fills an essential data gap regarding the genetic diversity of the species and its connectivity to other feeding grounds in the Pacific Ocean. The French Polynesian populations appear to be important contributors to the overall genetic diversity of the species, isolated from other Pacific populations, thus making them essential within the Pacific region. These results have important implications for the conservation of the species at both local and regional scales.

Threatened North African seagrass meadows have supported green turtle populations for millennia

"Protect and restore ecosystems and biodiversity" is the second official aim of the current UN Ocean Decade (2021 to 2030) calling for the identification and protection of critical marine habitats. However, data to inform policy are often lacking altogether or confined to recent times, preventing the establishment of long-term baselines. The unique insights gained from combining bioarchaeology (palaeoproteomics, stable isotope analysis) with contemporary data (from satellite tracking) identified habitats which sea turtles have been using in the Eastern Mediterranean over five millennia. Specifically, our analysis of archaeological green turtle (Chelonia mydas) bones revealed that they likely foraged on the same North African seagrass meadows as their modern-day counterparts. Here, millennia-long foraging habitat fidelity has been directly demonstrated, highlighting the significance (and long-term dividends) of protecting these critical coastal habitats that are especially vulnerable to global warming. We highlight the potential for historical ecology to inform policy in safeguarding critical marine habitats.

Population structure of Pacific green turtles: a new perspective from microsatellite DNA variation

This study builds upon the current understanding of green turtle population genetic structure in the Pacific that has largely been based on mitochondrial DNA (mtDNA), by examining nuclear DNA (nDNA) diversity, regional connectivity, and male-mediated gene flow. A total of 1,111 nesting green turtle samples were analyzed with 10 microsatellite markers from 20 Pacific rookeries. Population differentiation (FST) was significant (p &amp;lt;0.05) in all but 8 of 190 pairwise rookery comparisons. PairwiseFSTvalues and discriminant analysis of principal components (DAPC) revealed a defined East-West split consistent with mtDNA studies. Additionally, isolation-by-distance was evaluated with estimated effective migration surfaces (EEMS). The data indicated structure throughout the Pacific rookeries largely in agreement with stock structure defined by mtDNA studies, except for some areas on the Central American and Australian continental shelves, providing evidence of possible male-mediated gene flow. The series of analyses performed did indicate that male-mediated gene flow has likely occurred where breeding migration corridors of separate populations overlap with courtship areas. This may occur primarily along the margins of continents, including along Mexico and Central America in the East Pacific. Our study provides an ocean-wide baseline nDNA dataset for green turtle rookeries in the Pacific and reexamines the current thinking regarding the role of male turtles in the population dynamics of management units (MU) and to what extent nuclear gene flow occurs among designated MUs.

Macrophyte species richness improves resilience to grazing

Abstract Grazing pressure is increasing in the northern Gulf of Mexico due to tropicalization (i.e. range expansion of tropical species) and conservation efforts. Populations of herbivorous parrotfish, green turtles and manatees are all increasing in this region, and overgrazing can lead to loss of foundation species and their associated ecosystem services. With environmental conditions changing rapidly and seagrass abundance declining in many regions globally, understanding mechanisms that promote seagrass resilience to stressors (e.g. grazing) will be crucial for managing and restoring seagrass meadows and the valuable ecosystem services they provide. Diverse communities often exhibit higher resilience due to positive interactions and increased response diversity (i.e. differing reactions to environmental change), indicating that diversity may provide a tool for enhancing seagrass resilience. To investigate how macrophyte species richness influences resilience to increased grazing pressure, we simulated green turtle grazing events every 2 weeks for 8 weeks in plots that naturally varied in species richness. We recorded macrophyte metrics between the simulated grazing events and after a longer 4‐week recovery period. Both species identity and species richness impacted response to simulated herbivory. Four weeks after the last simulated grazing event, plots with higher species richness had recovered macrophyte shoot density better than plots with lower species richness, indicating that species richness may increase resilience. The grazing events had the strongest negative impact on the persistent species (i.e. longer‐lived species with slower shoot turnover), Thalassia testudinum, reducing T. testudinum density and dominance and indicating that areas dominated by this species may be the most negatively impacted by increased grazing pressure. Synthesis: Our results showed a positive impact of species richness on resilience and indicated that persistent seagrass species may have reduced dominance following repeated disturbances. Diverse seagrass beds can, therefore, improve ecosystem stability by allowing opportunistic species to replace species that are most negatively impacted by disturbances. These findings can be used to incorporate resilience into ecosystem management and identify seagrass beds that may be less resilient to changing environmental conditions.

Green Sea Turtles (Chelonia mydas) Accumulate Heavy Metals Near a Former Skeet Shooting Range in Kailua, O'ahu, Hawai'i.

The present study determined if green sea turtles (Chelonia mydas) in Kailua Bay, Oahu, in the Hawaiian Islands have elevated blood and scute lead (Pb), arsenic (As), and antimony (Sb) concentrations resulting from lead deposition at a historic skeet shooting range. Blood and scute samples were collected and analyzed for Pb, As, and Sb via inductively coupled plasma-mass spectrometry. Prey, water, and sediment samples were also analyzed. Turtle samples in Kailua Bay (45) have blood Pb concentrations (328 ± 195 ng/g) greater than a reference population (Howick Group of Islands, 29.2 ± 17.1 ng/g). Compared with other green turtle populations, only turtles in Oman, Brazil, and San Diego, CA have blood Pb concentrations greater than turtles in Kailua Bay. The estimated daily exposure of Pb from algae sources in Kailua Bay (0.12 mg/kg/day) was significantly lower than the no observed adverse effect level (100 mg/kg) of red-eared slider turtles. However, the chronic effects of Pb on sea turtles is poorly understood and continued monitoring of this population will increase our understanding of the Pb and As loads of sea turtles in Kailua Bay. Environ Toxicol Chem 2023;42:1109-1123. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.