Movement patterns of large juvenile loggerhead turtles in the Mediterranean Sea: Ontogenetic space use in a small ocean basin

Spatiotemporal Analysis of Stranded Loggerhead Sea Turtles on the Croatian Adriatic Coast

This study investigates the spatiotemporal trends of loggerhead turtles along the Croatian Adriatic coast by using stranding data and post-mortem analyses. Information on 620 loggerhead turtles (Caretta caretta), collected in the period between 2010 and 2022, has been analysed. Seasonal stranding variations reveal distinct patterns, indicating season-specific abundance and age-specific mortality in different areas, particularly in the key neritic habitat of the northern Adriatic. The analysis identifies four critical areas in the northeast and central Adriatic showing high stranding densities and provides regional managers with a tool with which to effectively conserve and manage this species. Fishing-induced mortality, collision with vessels, and potential cold stunning are identified as major threats to loggerhead turtles. Post-mortem investigations reveal that longline fishing gear and collisions with vessels are significant age-specific mortality contributors, underscoring the need for targeted conservation efforts in high-risk areas. The study acknowledges potential biases in strandings records but highlights the importance of post-mortem investigations in understanding mortality causes. The findings provide valuable insights for improving conservation strategies, emphasizing the importance of focused surveillance and conservation efforts in identified high-risk locations to mitigate human-turtle interactions.

Occurrence and pattern of legacy and emerging per- and Poly-FluoroAlkyl substances (PFAS) in eggs of loggerhead turtle Caretta caretta from western Mediterranean

Per-and Poly-FluoroAlkyl Substances (PFAS) are a class of persistent, toxic, and mobile and chemicals both from industrial sources and from the use and disposal of Consumers products containing PFAS, whose concentration in marine food webs could pose a toxicological risk for biota and humans. In 2021, unhatched eggs were sampled from 41 loggerhead turtle Caretta caretta nests from the Italian shores of the Campania Region (Southern Italy). Whole eggs were analysed for the presence of 66 legacy and emerging PFAS with Liquid Chromatography coupled to Hybrid High Resolution Mass Spectrometry. A median Σ66 Per- and Poly-FluoroAlkyl Substances value of 3.34 ng/g egg fresh weight was found; perfluoroctane sulfonate (PFOS) represented the most contributing congener (47%), followed by perfluoro-n-undecanoic acid, perfluoro-n-tridecanoic acid, perfluoro-n-decanoic acid, perfluoro-n-decanoic acid, and perfluoro-n-tetradecanoic acid, respectively. Such compounds showed a log-norm distribution, suggesting found concentrations could represent the baseline levels in the considered sampling area. Emerging ChloroPolyFluoroPolyEthers Carboxylic Acids (ClPFECAs) were found in 20 out of 41 samples in the range 0.01-1.59 ng/g. Four samples had 20-100 fold higher concentration compared to that of other samples, suggesting the presence of hot spot areas possibly related to presence of fluoropolymer-based marine litter turtles may ingest. The analysis of two paired eggs/liver samples recovered from stranded animals revealed PFAS concentration in the same order of magnitude, supporting the role of vitellogenin in their selective transfer to yolk. Significant (P = 0.0155) Kendall negative correlation coefficient of -0.2705 among PFOS content in eggs and the recorded hatching success prompts for further investigation on associated exposure assessment and related eco-toxicity risk. This work reports for the first time PFAS presence in georeferenced loggerhead turtle eggs of the Mediterranean Sea and results represent a starting point to study PFAS time-trends in this vulnerable species.

Levels of non-dioxin-like PCBs (NDL-PCBs) in liver of loggerhead turtles (Caretta caretta) from the Tyrrhenian Sea (Southern Italy)

The levels of six non-dioxin-like polychlorinated biphenyls (PCBs 28, 52, 101, 138, 153, and 180) were determined in the liver of 84 loggerhead turtles (Caretta caretta) stranded along the coasts of the Tyrrhenian Sea in Campania Region (Southern Italy), from 2017 to 2021. The average value of the sum (∑₆PCB_IND) was 28.0 ± 52.2 ng/g (w.w.). The hexachlorobiphenyls PCB 153 and PCB 138 and the heptachlorobiphenyl PCB 180 were the main contributors to the ∑₆PCB_IND. A weak positive correlation was found between CCL and highly chlorinated PCBs, with adult females having lower PCB concentrations than juvenile females and adult males. This study provides more comprehensive information on the levels of NDL-PCB in Mediterranean loggerhead turtles and sets the basis for assessing anthropogenic impacts on this species.

Phthalate esters (PAEs) concentration pattern reflects dietary habitats (δ13C) in blood of Mediterranean loggerhead turtles (Caretta caretta)

Phthalic acid esters (PAEs) are classified as endocrine disruptors, but it remains unclear if they can enter the marine food-web and result in severe health effects for organisms. Loggerhead turtles (Caretta caretta) can be chronically exposed to PAEs by ingesting plastic debris, but no information is available about PAEs levels in blood, and how these concentrations are related to diet during different life stages. This paper investigated, for the first time, six PAEs in blood of 18 wild-caught Mediterranean loggerhead turtles throughout solid-phase extraction coupled with gas chromatography-ion trap/mass spectrometry. Stable isotope analyses of carbon and nitrogen were also performed to assess the resource use pattern of loggerhead turtles. DEHP (12-63 ng mL^-1) and DBP (6-57 ng mL^-1) were the most frequently represented PAEs, followed by DiBP, DMP, DEP and DOP. The total PAEs concentration was highest in three turtles (124-260 ng mL^-1) whereas three other turtles had concentrations below the detection limit. PAEs were clustered in three groups according to concentration in all samples: DEHP in the first group, DBP, DEP, and DiBP in the second group, and DOP and DMP in the third group. The total phthalates concentration did not differ between large-sized (96.3 ± 86.0 ng mL^-1) and small-sized (67.1 ± 34.2 ng mL^-1) turtles (p < 0.001). However, DMP and DEP were found only in large-sized turtles and DiBP and DBP had higher concentrations in large-sized turtles. On the other hand, DEHP and DOP were found in both small- and large-sized turtles with similar concentrations, i.e. ~ 21.0/32.0 ng mL^-1 and ~ 7^.1/9.9 ng mL^-1, respectively. Winsored robust models indicated that δ¹³C is a good predictor for DBP and DiBP concentrations (significant Akaike Information criterion weight, AIC_wt). Our results indicate that blood is a good matrix to evaluate acute exposure to PAEs in marine turtles. Moreover, this approach is here suggested as a useful tool to explain the internal dose of PAEs in term of dietary habits (δ¹³C), suggesting that all marine species at high trophic levels may be particularly exposed to PAEs, despite their different dietary habitats and levels of exposure.

Total Arsenic Concentrations in Sea Turtle Tissues from the Mediterranean Coast of Spain

In this work we studied total arsenic concentrations in liver, muscle and kidney of 49 individuals of two sea turtle species (loggerhead sea turtles, n = 45; leatherback turtles, n = 4) stranded in Murcia (South-eastern Spain) coastline between 2009 and 2018. In accordance with the literature, muscle was the tissue with the highest concentrations in both species, followed by liver and kidney. Although differences in arsenic concentrations were not statistically significant between the study species, loggerhead sea turtles showed concentrations two or three times higher than those of leatherback turtles, which we attribute to differences on feeding behavior and habitat preferences. Arsenic concentrations in turtles from this area increase evidence of western Mediterranean Sea as a hotspot for metal pollution. Based on the scarce existing knowledge on arsenic toxicity in sea turtles, those levels found in our study are below those responsible for liver damage.