A Global Analysis of Anthropogenic Development of Marine Turtle Nesting Beaches

Hawksbill Sea Turtle (Eretmochelys imbricata) Blood and Eggs Organochlorine Pesticides Concentrations and Embryonic Development in a Nesting Area (Yucatan Peninsula, Mexico)

Environmental contaminants with chemical origins, such as organochlorine pesticides (OCPs) have major impacts on the health of marine animals, including sea turtles, due to the bioaccumulation of those substances by transference throughout the food chain. The effects of environmental pollution on the health of marine turtles are very important for management strategies and conservation. During recent decades, the south Gulf of Mexico and the Yucatan Peninsula have suffered from increasingly frequent disturbances from continental landmasses, river systems, urban wastewater runoff, port areas, tourism, industrial activities, pesticides from agricultural use, and other pollutants, such as metals, persistent organic pollutants (POPs) and hydrocarbons (from the oil industry activities), which contaminate water and sediments and worsen the environmental quality of the marine ecosystem in this region. In this study, we assessed the concentrations of OCPs in the blood and eggs of 60 hawksbill turtles (Eretmochelys imbricata) nesting at the Punta Xen turtle camp, and their effects on the nesting population's reproductive performance: specifically, maternal transfer and embryonic development were analyzed. Hematologic characteristics, including packed cell volume, white blood cell count, red blood cell count, and haemoglobin levels, and plasma chemistry values, including creatinine, blood urea nitrogen, uric acid, triglyceride, total cholesterol and glucose, were also measured. The general health of the turtles in this study, as well as their levels of urea, serum creatinine, glucose, uric, acid, cholesterol, and triglyceride, fell within normal ranges and was similar to other normal values, which could indicate the turtles' good energy levels and body conditions for nest-building activity, with all of the turtles able to successfully come ashore to nest. All the same, the obtained results also indicate that OCPs affect the nesting and reproductive performance of the hawksbill turtles, as well as their fertility and the development of the population of eggs and reproductive performance, specifically in terms of maternal transference and embryonic development. There were significant differences in the concentrations of OCPs (ΣHCHs and ΣDienes) between maternal blood and eggs, indicating that these chemicals are transferred from nesting females to eggs and, ultimately, to hatchlings. OCPs may, therefore, have an effect on the health and reproductive performance of hawksbill turtles, both in terms of their fertility and egg development. Conservation strategies need to be species-specific, due to differences in feeding, and address the reasons for any decline, focusing on regional assessments. Thus, accurate and comparable monitoring data are necessary, which requires the standardization of monitoring protocols.

Geo-ecological cues for mass nesting synchronization of Olive Ridley turtles along Rushikulya estuary in Odisha, east coast of India

In this study, we have analyzed how geo-ecological cues for endangered Olive Ridley turtles' mass nesting behavior got modified by impact of four severe cyclones during 2010-2019 that made landfall in the vicinity of Rushikulya estuary, which is one of the largest mass nesting congregation (arribada) sites in the world. Analyzing last 10 years of shoreline dynamics, we show that even the slightest modification in beach morphology influenced their nesting behavior in Rushikulya rookery. Shoreline change analysis showed periodic phases of high/low erosion and the northward longshore sediment movement, which becomes impeded by the southern spit, the length of which increased by about 1800 m. During the analyzed period, the nesting behavior of Olive Ridley turtle was greatly influenced by changes in land use and land cover pattern around the Rushikulya rookery. Such reductions in tree cover and marshy land areas were majorly driven by anthropogenic activities and extreme weather events, such as cyclones. We also report increased mortality of turtles, no or false mass nesting events due to significant loss and/or erosion of the nesting sites due to cyclones. The results indicate that conservation of Olive Ridley turtles should be more holistic, or ecosystem centric, rather than species centric. It is important to maintain the ecological integrity of their habitat for highly synchronized mass nesting event and eventually their survival.

Climate change and marine turtles: recent advances and future directions

Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.