In this study, we applied multiple reaction monitoring (MRM)-profiling to explore the relative ion intensity of lipid classes in plasma samples from sea turtles in order to profile lipids relevant to ...sea turtle physiology and investigate how dynamic ocean environments affect these profiles. We collected plasma samples from foraging green (Chelonia mydas, n = 28) and hawksbill (Eretmochelys imbricata, n = 16) turtles live captured in North Pacific Costa Rica in 2017. From these samples, we identified 623 MRMs belonging to 10 lipid classes (sphingomyelin, phosphatidylcholine, free fatty acid, cholesteryl ester, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine, ceramide, and triacylglyceride) and one metabolite group (acyl-carnitine) present in sea turtle plasma. The relative ion intensities of most lipids (80%) were consistent between species, across seasons, and were not correlated to body size or estimated sex. Of the differences we observed, the most pronounced was the differences in relative ion intensity between species. We identified 123 lipids that had species-specific relative ion intensities. While some of this variability is likely due to green and hawksbill turtles consuming different food items, we found indications of a phylogenetic component as well. Of these, we identified 47 lipids that varied by season, most belonging to the structural phospholipid classes. Overall, more lipids (n = 39) had higher relative ion intensity in the upwelling (colder) season compared to the non-upwelling season (n = 8). Further, we found more variability in hawksbill turtles than green turtles. Here, we provide the framework in which to apply future lipid profiling in the assessment of health, physiology, and behavior in endangered sea turtles.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We used stable isotopes to investigate isotopic niche size, overlap, and diet composition in green (black and yellow morphotype
Chelonia mydas
; 50.0 to 95.0 cm curved carapace length, CCL) and ...hawksbill turtles (
Eretmochelys imbricata
; 38.5 to 83.0 cm CCL) in a recently described foraging habitat in North Pacific Costa Rica. We measured whole blood stable carbon (δ
13
C) and nitrogen (δ
15
N) ratios in black (
n
= 39; mean ± SD, − 16.54 ± 0.66‰ and 14.39 ± 0.77‰), yellow (
n
= 13; − 15.74 ± 0.65‰ and 12.37 ± 0.55‰) and hawksbill turtles (
n
= 13; − 16.23 ± 1.34‰ and 12.63 ± 0.32‰) and skin δ
13
C and δ
15
N values in black (
n
= 36; − 15.32 ± 0.79‰ and 15.16 ± 0.72‰), yellow (
n
= 12; − 15.38 ± 0.91‰ and 13.78 ± 0.75‰) and hawksbill turtles (
n
= 10; − 14.33 ± 1.49‰ and 13.77 ± 0.29‰). Isotopic niche space revealed distinctly higher δ
15
N area in black turtles and significant overlap between yellow and hawksbill turtles, and a recent shift in diet in yellow turtles from omnivory to herbivory. In black turtles, isotopic niche suggests individual specialization during the non-upwelling season and generalization in diet during the upwelling season. Mixing model results suggest that black turtles forage at multiple trophic levels (fish: 34.8 ± 10.1% of diet and macroalgae: 51.8 ± 12.8% of diet), while yellow and hawksbill turtles primarily forage on macroalgae (85.0 ± 6.6% in yellow turtles and 85.1 ± 5.9% in hawksbill turtles). These results add to a growing understanding that diet in sea turtles is influenced by diet items present in the environment and suggest that black turtles are potential tertiary consumers.
Satellite telemetry was used to track inter-nesting, post-nesting, and foraging movements of six green turtles that nested on Bioko Island, Equatorial Guinea at the end of the 2019 nesting season, as ...well as foraging movements of five green turtles after the 2018 nesting season (
n
= 11 across two seasons), from the same nesting population. These tracks were fit with a switching state-space model to characterize movements and then analyzed in relation to environmental and anthropogenic factors. Inter-nesting movements of two turtles included separate oceanic loops, in which turtles traveled > 40 km away from nesting beaches. Four complete migrations were observed to two distinct foraging grounds, with two turtles migrating west for an average of 1064 km to the coastal waters of Ghana, and two migrating south for an average of 1563 km to a newly discovered foraging ground in the coastal waters of Angola. All migrations included intermittent foraging at stopover sites, including one period of possible oceanic foraging. Turtles at both foraging grounds maintained distinct core use areas in shallow, near-shore (< 20 km from coast) waters. Spatial and depth data reveal critical habitats for this population throughout inter-nesting, post-nesting, and foraging behaviors. Tracks spanned nine countries, highlighting the need for multi-national cooperation in the development of marine conservation management plans in the area. The long distances covered by these turtles suggests that fisheries bycatch and direct harvest throughout the East Atlantic may impact this population. Additionally, spatial and dive depth data can inform zonal fishing regulations and provide the information needed to modify fishing practices and gear in ways likely to reduce sea turtle bycatch.
Sea turtles, like other air-breathing diving vertebrates, commonly experience significant gas embolism (GE) when incidentally caught at depth in fishing gear and brought to the surface. To better ...understand why sea turtles develop GE, we built a mathematical model to estimate partial pressures of N
2
(PN
2
), O
2
(PO
2
), and CO
2
(PCO
2
) in the major body-compartments of diving loggerheads (
Caretta caretta
), leatherbacks (
Dermochelys coriacea
), and green turtles (
Chelonia mydas
). This model was adapted from a published model for estimating gas dynamics in marine mammals and penguins. To parameterize the sea turtle model, we used values gleaned from previously published literature and 22 necropsies. Next, we applied this model to data collected from free-roaming individuals of the three study species. Finally, we varied body-condition and cardiac output within the model to see how these factors affected the risk of GE. Our model suggests that cardiac output likely plays a significant role in the modulation of GE, especially in the deeper diving leatherback turtles. This baseline model also indicates that even during routine diving behavior, sea turtles are at high risk of GE. This likely means that turtles have additional behavioral, anatomical, and/or physiologic adaptions that serve to reduce the probability of GE but were not incorporated in this model. Identifying these adaptations and incorporating them into future iterations of this model will further reveal the factors driving GE in sea turtles.
Sea turtles are an iconic group of marine megafauna that have been exposed to multiple anthropogenic threats across their different life stages, especially in the past decades. This has resulted in ...population declines, and consequently many sea turtle populations are now classified as threatened or endangered globally. Although some populations of sea turtles worldwide are showing early signs of recovery, many still face fundamental threats. This is problematic since sea turtles have important ecological roles. To encourage informed conservation planning and direct future research, we surveyed experts to identify the key contemporary threats (climate change, direct take, fisheries, pollution, disease, predation, and coastal and marine development) faced by sea turtles. Using the survey results and current literature, we also outline knowledge gaps in our understanding of the impact of these threats and how targeted future research, often involving emerging technologies, could close those gaps.
As ectothermic marine megafauna, sea turtle physiology and ecology are tightly intertwined with temperature, seasonality, and oceanography. Identifying how turtles respond when exposed to cold water, ...how they adapt to cold environments when they need to explore cold environments in order to forage, and what foraging resources are exploited by sea turtles are all components central to their conservation. Cold-stunning is a welldocumented phenomenon that occurs when water induced decreases in sea turtle body temperature cause turtles to become immobilized and wash ashore. While most coldstunned turtles are rescued and rehabilitated, we do not know whether cold-stunning is an acute transient occurrence, or a symptom of a bigger environmental problem. Further, while in some environments avoiding cold water is preferential, in other habitats, sea turtles need to inhabit cold environments in order to forage. Along the Eastern Pacific Rim, discrete upwelling locations are characterized by high primary productivity and unusually cold water. In these environments, avoidance is not possible and sea turtles require physiological adaptions to mitigate body temperature decreases in cold water. Little is known about how turtles handle upwelling environments, despite the fact that sea turtles remain in these habitats regardless of water temperature fluctuations. Because upwelling habitats provide increased nutrient presence, and sea turtles are opportunistic foragers, quantification of diet composition will further our understanding of why sea turtles remain in cold water environments year-round. Diet composition in multiple populations of cohabitating sea turtles revealed partitioning that results in reduced inter-specific competition. Further, flexibility in diets provides a wide range of ecosystem services central to habitat resiliency. Therefore, conservation of endangered sea turtles requires complete ecosystem conservation, and complete understanding of the interconnectivity of sea turtles and their environments is crucial.
The East Pacific green turtle (Chelonia mydas agasizzi) is a sub-population of the widely distributed green turtle (Chelonia mydas). Like all sea turtles, East Pacific green turtles have a type III ...survivorship curve, which is characterized by long-lived adults that have a low mortality rate and high reproductive output with a low hatchling survival rate. For this to be successful, the adults must live through multiple reproductive seasons, and in the Eastern Pacific, there is high mortality on adult East Pacific green sea turtles. The continued success of this distinct population relies on protection during key in water movements: the nesting season and migrations from foraging grounds to nesting beaches and back. Management techniques need to be developed on a site-specific basis so it is crucial to understand the specific habitat needs for each nesting population as defined by the local oceanography. I used satellite telemetry to map movements of Pacific green turtles nesting on Playa Cabuyal, Costa Rica to understand the temporal and physical distribution of turtles both two and three dimensionally during the inter-nesting period and post-nesting migrations to foraging grounds. I deployed ten satellite transmitters across two nesting seasons, 2012-2014, six SPOT5 transmitters and four MK10 transmitters. The sample size for this study included 11 inter-nesting turtles and four post-nesting migrations (two post-nesting turtles were also tracked during their nesting season), curved carapace length ranged from 82.2 to 91.6 cm (mean ± SD = 85±2.84 cm) while curved carapace width ranged from 76 to 90 cm (mean ± SD = 79.5±3.80 cm). The observed inter-nesting period was between 7 and 17 days (mean ± SD, 13.1±2.5 days), which is comparable to the mean of 15.4 days observed as an average inter-nesting interval for turtles nesting on this beach. Post-nesting turtles moved over a period of 19 to 189 days (107.25±90.77 days) with one resident of the Gulf of Papagayo and three that migrated an average of 500 km away from the nesting beach. During the inter-nesting period turtles spread out across the Gulf of Papagayo and, in some cases, migrated out of the gulf and along the coast before returning to nest. The minimum convex polygon (MCP) with percent area use contours indicates that the highest use areas were close to the beach (within 10 km) and a couple isolated areas off the coast in the southern part of the gulf. Overall, this high use inter-nesting area totals 27 km2 and represents the high density twenty-five percent (75% of all positions received) of recorded location data during their movements between nests. Inter-nesting dive behavior indicated that, on average, fifty-five percent of the dives recorded were in the top 15 m of the water column, and sixty-six percent of inter-nesting dives lasted 30 minutes or less. Overall, ninety percent of the time inter-nesting turtles were within 15 m of the surface even though the ocean floor is generally 25 m or deeper throughout the Gulf of Papagayo. The oceanographic characteristic that limited turtles' dive behavior was the water temperature. The temperatures experienced at varying depths changed as the nesting season progressed showing a significantly shallower thermocline in the spring months when compared to the winter months of this study. In December and January the temperature at the surface temperature was 28 °C and stayed above 25 °C to depths of 25 m. In February and March the surface temperature was 25 °C and at 25 m the temperature had already dropped below 20 °C. Turtle behavior changed to reflect this shift in the water temperature with more time spent in the Surface - 5 m depth bin during February–March as compared to December when the waters at depth were warmer. Post-nesting turtles took up residence in locations along the Costa Rica, Nicaragua, El Salvadoria and Guatemala coasts; a pattern similar to other Pacific green turtles nesting more to the South along the Pacific coast of Costa Rica. During migration, the turtles remained within 50 km of the coastline, which allowed them to stay in shallow warmer coastal waters. Dive behavior of these post-nesting turtles shows a bimodal distribution in depth use not previously described for this sub-population, with peak dive depths of 11 to 15 m and 46 to 50 m. This could be indicative of foraging while migrating. Currents are one of the most important factors in migration routes because they determine hatchling dispersal and locations of primary productivity. Chlorophyll distribution was correlated to the post-nesting movements of one turtle. Conservation efforts should focus on regulating the fishing efforts in the area of inter-nesting habitats and migratory corridors because by-catch mortality pressure on adults is currently the biggest threat to the population. By providing the local fisheries with depth integration levels and dates of passage, the set of nets and long lines could be below these normal behaviors and reduced during migration dates to reduce bycatch and fisheries interactions. Fishing regulations need to be enforced and regulated locally on site-by-site bases, eliciting the help of each country and community. Future work with this inter-nesting and post-nesting data will be to analyze the turtle interaction points with local and international fisheries in hopes of generating a management strategy through cooperation along the Eastern Pacific
Sea turtles generally lay several clutches of eggs in a single nesting season. While a negative correlation between water temperatures and the time required between constitutive nesting events ...(termed the internesting interval) has been previously reported in loggerhead Caretta caretta and green turtles Chelonia mydas, it is not understood whether this relationship remains constant across other sea turtle species. Here, we expanded upon these previous studies on loggerhead and green turtles by using larger sample sizes and including data from species with a wider range of body-sizes; specifically: hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, and olive ridley turtles Lepidochelys olivacea. In total, we compiled temperature data from biologgers deployed over internesting intervals on 23 loggerhead, 22 green, 7 hawksbill, 26 leatherback and 11 olive ridley turtles from nesting sites in 8 different countries. The relationship between the duration of the internesting interval and water temperatures in green and loggerhead turtles were statistically similar yet it differed between all other turtle species. Specifically, hawksbill turtles had much longer internesting intervals than green or loggerhead turtles even after controlling for temperature. In addition, both olive ridley and leatherback turtles exhibited thermal independence of internesting intervals presumably due to the large body-size of leatherback turtles and the unique capacity of ridley turtles to delay oviposition. The observed interspecific differences in the relationship between the length of the internesting interval and water temperatures indicate the complex and variable responses that each sea turtle species may exhibit due to environmental fluctuations and climate change.
•Water temperature assumed to effect internesting interval duration in sea turtles.•Temperature data from biologgers deployed on 89 sea turtles across 5 species.•Correlation only observed in green and loggerhead turtles.•Varying effect of temperature between taxa has implications for climate change.
As ectothermic marine megafauna, sea turtle physiology and ecology are tightly intertwined with temperature, seasonality, and oceanography. Identifying how turtles respond when exposed to cold water, ...how they adapt to cold environments when they need to explore cold environments in order to forage, and what foraging resources are exploited by sea turtles are all components central to their conservation. Cold-stunning is a well-documented phenomenon that occurs when water induced decreases in sea turtle body temperature cause turtles to become immobilized and wash ashore. While most cold-stunned turtles are rescued and rehabilitated, we do not know whether cold-stunning is an acute transient occurrence, or a symptom of a bigger environmental problem. Further, while in some environments avoiding cold water is preferential, in other habitats, sea turtles need to inhabit cold environments in order to forage. Along the Eastern Pacific Rim, discrete upwelling locations are characterized by high primary productivity and unusually cold water. In these environments, avoidance is not possible and sea turtles require physiological adaptions to mitigate body temperature decreases in cold water. Little is known about how turtles handle upwelling environments, despite the fact that sea turtles remain in these habitats regardless of water temperature fluctuations. Because upwelling habitats provide increased nutrient presence, and sea turtles are opportunistic foragers, quantification of diet composition will further our understanding of why sea turtles remain in cold water environments year-round. Diet composition in multiple populations of cohabitating sea turtles revealed partitioning that results in reduced inter-specific competition. Further, flexibility in diets provides a wide range of ecosystem services central to habitat resiliency. Therefore, conservation of endangered sea turtles requires complete ecosystem conservation, and complete understanding of the interconnectivity of sea turtles and their environments is crucial.
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