Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: (1) a nominal approach through discriminant analysis and (2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively determine geographic origin for large numbers of untracked individuals. Regular monitoring of sea turtle nesting aggregations with stable isotope sampling can be used to fill critical data gaps regarding habitat use and migration patterns. Probabilistic assignment to origin with isoscapes has not been previously used in the marine environment, but the methods presented here could also be applied to other migratory marine species.

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The gut microbiome of herbivorous animals consists of organisms that efficiently digest the structural carbohydrates of ingested plant material. Green turtles (Chelonia mydas) provide an interesting model of change in these microbial communities because they undergo a pronounced shift from a surface-pelagic distribution and omnivorous diet to a neritic distribution and herbivorous diet. As an alternative to direct sampling of the gut, we investigated the cloacal microbiomes of juvenile green turtles before and after recruitment to neritic waters to observe any changes in their microbial community structure. Cloacal swabs were taken from individual turtles for analysis of the 16S rRNA gene sequences using Illumina sequencing. One fecal sample was also obtained, allowing for a preliminary comparison with the bacterial community of the cloaca. We found significant variation in the juvenile green turtle bacterial communities between pelagic and neritic habitats, suggesting that environmental and dietary factors support different bacterial communities in green turtles from these habitats. This is the first study to characterize the cloacal microbiome of green turtles in the context of their ontogenetic shifts, which could provide valuable insight into the origins of their gut bacteria and how the microbial community supports their shift to herbivory.

Characterization of a population of green turtles inhabiting the northeastern Gulf of Mexico was made possible by the mortality of a subset of > 4500 sea turtles that stranded during a mass cold stunning event in Florida, USA, during January 2010. In total, 434 dead, stranded green turtles Chelonia mydas were evaluated through necropsy and skeletochronological analysis to characterize morphology, sex, body condition, disease status, age structure, and growth patterns. Standard straightline carapace lengths ranged from 18.1 to 78.5 cm (mean ± SD = 36.3 ± 10.4 cm) and did not significantly differ from those of stranded green turtles that survived this event. Prevalence of fibropapilloma (FP) was low, at 6%, and sex ratio was significantly biased toward females (2.45F:1M). Age estimates ranged from 2 to 22 yr (mean ± SD = 9 ± 4 yr) and female age distribution was significantly greater than that of males. Mean stage durations, as calculated through sum mation of size class-specific growth rates and fitting smoothing spline models to length-at-age data, were similar and ranged from 17 to 20 yr. Generalized additive models and generalized additive mixed models were used to assess the potential influence of discrete and continuous covariates on growth rates. Somatic growth was significantly influenced by size, age, and calendar year; however, no effect of sex, FP status, or body condition was found. Increased understanding of population parameters will improve population models for the species and can also serve as a reference for assessing potential effects of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. 458: 213-229, 2012 mation was recently emphasized in the aftermath of the April 20, 2010, Deepwater Horizon (DWH) MC-252 oil spill in the Gulf of Mexico during initiation of efforts to assess the effects to sea turtles of this catastrophic event (Bjorndal et al. 2011, Crowder & Heppell 2011. However, collection of these data is made difficult by deficiencies in the ability to assess sea turtle populations in an unbiased manner (Heppell et al. 2003). Population characterizations based on nesting beach studies, while prevalent due to the relative accessibility of the females on the beach, are necessarily focused in their scope (NRC 2010). In-water studies are often restricted to limited geographic areas (Bjorndal & Bolten 2000) and the proportion of individuals available to be sampled can be influenced by stage-and population-specific partitioning of habitat use (Musick & Limpus 1997, Plotkin 2003 and sex-specific behavior (Wibbels 2003). In addition, the time frames over which data collection must occur to adequately assess population parameters for these generally slow-to-mature, long-lived species are daunting (Heppell et al. 2003). OPEN PEN ACCESS CCESSMar Ecol Prog SerLife history data obtained from dead, stranded sea turtles can be informative, but often need to be interpreted with caution given the general lack of information regarding cause of death (natural vs. anthropogenic) (NRC 2...

Tropicalization is a term used to describe the transformation of temperate ecosystems by poleward-moving tropical organisms in response to warming temperatures. In North America, decreases in the frequency and intensity of extreme winter cold events are expected to allow the poleward range expansion of many cold-sensitive tropical organisms, sometimes at the expense of temperate organisms. Although ecologists have long noted the critical ecological role of winter cold temperature extremes in tropicaltemperate transition zones, the ecological effects of extreme cold events have been understudied, and the influence of warming winter temperatures has too often been left out of climate change vulnerability assessments. Here, we examine the influence of extreme cold events on the northward range limits of a diverse group of tropical organisms, including terrestrial plants, coastal wetland plants, coastal fishes, sea turtles, terrestrial reptiles, amphibians, manatees, and insects. For these organisms, extreme This article has been contributed to by US Government employees and their work is in the public domain in the USA.