Trophic behavior of inorganic elements in nesting sea turtles (Chelonia mydas, Eretmochelys imbricata, and Caretta caretta) in Quintana Roo: Biomagnification and biodilution effect in blood and scute tissues

Trace elements and high sulfur levels in the blood of rehabilitated eastern Mediterranean Sea green sea turtles (Chelonia mydas)

The Eastern Mediterranean Sea (EMS) exhibits high temperature and salinity, low levels of biologic production and is considered oligotrophic. Nonetheless, it is also a hotspot of biodiversity, with several important endangered flagship species, including several species of sea turtles. These turtles serve as bioindicators for the health of their ecologic systems, due to changes in diet, habitat and migration patterns that characterize different stages in their lives. This study covered 100 blood samples taken between 2008 and 2019 from 72 green sea turtles (Chelonia mydas) tested for 67 elements, some of which carry toxic potential. The turtles were treated at the Israeli Sea Turtle Rescue Center (ISTRC) after being rescued from sea, exhibiting a variety of health conditions and Injuries. The data were compared to similar studies worldwide and serve as a basis for monitoring the health status of the green sea turtles' EMS populations. The results of all animals presented noticeably high levels of sulfur - an order of magnitude higher than sea turtles from other locations around the world. This paper discusses the possible origins of this element, as well as its potential effects, while raising the question regarding the ability of these sea turtles to endure such sulfur levels.

Global mercury concentrations in biota: their use as a basis for a global biomonitoring framework

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention's progress to reduce the impact of global Hg pollution on people and the environment.

Biological and ecological traits rather than geography control mercury (Hg) in scutes of marine turtles from the Southwest Atlantic

The use of sentinel species in monitoring programs for toxic metals such as mercury (Hg) is essential to understand these pollutants' impact on the environment. For this purpose, it is essential to use organisms that have a lifespan compatible with the residence time of Hg in the oceans, and preferably with a wide geographical distribution, such as sea turtles. Here, we assess the regional variability of Hg concentrations using carapace scutes of four sea turtle species along the foraging and spawning area in the northeast coastline of Brazil. Mercury concentrations in samples showed no relationship with the environmental Hg levels (obtained from literature). Rather, Hg concentrations varied according to species-specific biological, and ecological traits. Characteristics such as the ontogenetic shift in the diet of Chelonia mydas, capital breeding in females, depth of foraging in oceanic waters, and selectivity of food items, such as in Eretmochelys imbricata, significantly influenced Hg concentrations.

A Pilot Study of Mercury Distribution in the Carapace of Four Species of Sea Turtles from Northeastern Brazil

Scutes present very complex morphologies with different growth rates at different areas of the carapace that can change the accumulation process of essential and non-essential metals. To infer the effects of morphology and growth on Hg concentrations in scutes, we mapped them in the carapace of one individual of four species of sea turtles sampled along the Brazilian coast. The results showed that Hg concentrations were higher in the vertebral scutes of Chelonia mydas and Eretmochelys imbricata suggesting variation in growth rates of different carapace areas since the vertebral area is the first to develop prior to costal areas. Caretta caretta and Lepidochelys olivacea did not show differences between carapace areas. The preliminary data from this pilot study indicate that vertebral scutes may be suitable for monitoring Hg in C. mydas and E. imbricata, since they reflect longer exposure period. A species-to-species comparison of Hg concentrations is not possible due to the small number of sampled individuals, nevertheless, E. imbricata showed remarkably lower Hg concentrations compared to the other three species. Further studies are required for all four species, with a larger number of individuals, preferentially of varying life stages, due to the unknown effects of different diets, Hg exposure, and migration histories.

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.