Monitoring green turtle population dynamics in Shoalwater Bay 2000-2004

The Great Barrier Reef Marine Park Authority (GBRMPA) and the Queensland Environmental Protection Agency (QEPA) are pleased to publish this report on the monitoring of a foraging ground population for the southern Great Barrier Reef green turtle genetic stock

Chapter 15: Vulnerability of marine reptiles in the Great Barrier Reef to climate change

Marine reptiles are an important and well-documented component of the Great Barrier Reef (GBR), comprising a single species of crocodile (Crocodylidae), six species of marine turtles (five Chelonidae and one Dermochelyidae), at least 16 species of sea snakes (Hydrophiidae), one species of file snake (Acrochordidae) and one species of mangrove snake (Colubridae). Together these marine reptile species inhabit or traverse through each of the 70 bioregions identified by the Great Barrier Reef Marine Park Authority Representative Areas Program . These marine reptile species, with the exception of some of the snakes, have distributions that span large areas of the GBR. Crocodiles, marine turtles, file snakes, mangrove snakes and sea snakes all have life history traits, behaviour and physiology that are strongly influenced by temperature. All are ectothermic except for the leatherback turtle and thus their body temperatures fluctuate with environmental temperature. For egg laying species (crocodiles and turtles), the temperature of the nest determines incubation period, hatching success and hatching sex ratio. Thus as a group they are potentially vulnerable to climate change.This is Chapter 15 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13

Investigating differences in population recovery rates of two sympatrically nesting sea turtle species

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability Statement: Data are available from corresponding author upon reasonable request.Estimating life‐history traits and understanding their variation underpins the management of long‐lived, migratory animals, while knowledge of recovery dynamics can inform the management of conservation‐dependent species. Using a combination of nest counts and individual‐based life‐history data collected since 1993, we explore the drivers underlying contrasting population recovery rates of sympatrically nesting loggerhead (Caretta caretta) and green (Chelonia mydas) turtles in North Cyprus. We found that nest counts of loggerhead and green turtles from 28 beaches across the island increased by 46% and 162%, respectively over the past 27 years. A Bayesian state‐space model revealed that, at our individual‐based monitoring site, nesting of green turtles increased annually at four times the rate of that of loggerhead turtles. Furthermore, we found that loggerhead turtles nesting at the individual‐based monitoring site had stable reproductive parameters and average adult survival for the species and are the smallest breeding adults globally. Based on results from multiple matrix model scenarios, we propose that higher mortality rates of individuals in all age classes (likely driven by differences in life history and interaction with fisheries), rather than low reproductive output, are impeding the recovery of this species. While the increase in green turtles is encouraging, the Mediterranean population is estimated to have around 3,400 adults and is restricted to the Eastern Basin. The recovery of loggerhead turtles is likely to be compromised until mortality rates in the region are adequately quantified and mitigated. As survival of immature individuals is a powerful driver for sea turtle population numbers, additional efforts should target management at pelagic and neritic foraging areas. Understanding threats faced by immature life stages is crucial to accurately parameterise population models and to target conservation actions for long‐lived marine vertebrates

Mitochondrial DNA control region polymorphisms: Genetic markers for ecological studies of marine turtles

We describe a rapid and sensitive method for the detection of population‐specific genetic markers in mitochondrial DNA (mtDNA) and the use of such markers to analyse population structure of marine turtles. A series of oligonucleotide primers specific for the amplification of the mtDNA control region in Cheloniid turtles were designed from preliminary sequence data. Using two of these primers, a 384–385‐bp sequence was amplified from the 5′ portion of the mtDNA control region of 15 green turtles Chelonia mydas from 12 different Indo‐Pacific rookeries. Fourteen of the 15 individuals, including some with identical whole‐genome restriction fragment patterns, had sequences that differed by one or more base substitutions. Analysis of sequence variation among individuals identified a total of 41 nucleotide substitutions and a 1‐bp insertion/deletion. Comparison with evidence from whole‐genome restriction enzyme analysis of the same individuals indicated that this portion of the control region is evolving approximately eight times faster than the average rate and that the sequence analysis detected approximately one fifth of the total variation present in the genome. Restriction enzyme analysis of amplified products from an additional 256 individuals revealed significant geographic structuring in the distribution of mtDNA genotypes among five of the 10 rookeries surveyed extensively. Additional geographic structuring of genotypes was identified through denaturing gradient gel electrophoresis (DGGE) of amplified products. Only two of the 10 rookeries surveyed could not be differentiated, indicating that the Indo‐Pacific C. mydas include a number of genetically differentiated populations, with minimal female‐mediated gene flow among them. Important applications for genetic markers in the conservation and management of marine turtles include the identification of appropriate demographic units for research and management (i.e. genetically discrete populations) and assessment of the composition of feeding and harvested populations

Conservation implications of internesting habitat use by Loggerhead Turtles Caretta caretta in Woongarra Marine Park, Queensland, Australia

We studied internesting habitat use by Loggerhead Turtles Caretta caretta with radio telemetry and by visual sightings of paint-marked turtles in Woongarra Marine Park, adjacent to the major mainland nesting rookery in Queensland. A high concentration of females occurs within the Park during the early phase of the internesting period as ovulation and shelling of eggs occur. From 36-72 hr following oviposition, activity ranges and swimming rates were greatly reduced. About day 9 after oviposition, turtles resumed higher swimming rates and wider activity ranges and were as likely to be outside protected management zones as within. Movements were generally within 10 km north or south of the rookery, limited to 1-2 km of the coast rather than offshore oriented and were independent of currents. A different pattern was exhibited after the final nest of the season: females departed the region quickly, with little of the localized movement characteristic of the internesting period. Over 89% of the nesting females were susceptible to trawling at some time during their internesting period as they swam outside the Protected Management Area. The likelihood of turtle-trawler interactions along the Woongarra coast and the potential of turtle excluder devices (TEDs) as a conservation measure are discussed. TED use provides a broadly applicable management option that can be combined with spatially or temporally restricted trawling zones

Past, current and future thermal profiles of green turtle nesting grounds: implications from climate change

Sex determination and hatching success in sea turtles is temperature dependent and as a result global warming poses a threat to sea turtles. Warmer sand temperatures may skew sea turtle population′s sex ratios towards predominantly females and decrease hatching success. Therefore, understanding the rates at which sand temperatures are likely to increase as climate change progresses is warranted. We recorded sand\ud temperature and used historical sea surface and air temperature to model past and to predict future sand\ud temperature under various scenarios of global warming at key sea turtle nesting grounds (n=7) used by the northern Great Barrier Reef (nGBR) green turtle, Chelonia mydas, population. Reconstructed temperatures from 1990 to the present suggest that sand temperatures at the nesting sites studied have not changed significantly during the last 18 years. Current thermal profile at the nesting grounds suggests a bias towards female hatchling production into this population. Inter-beach thermal variance was observed at some nesting grounds with open areas in the sand dune at northern facing beaches having the warmest incubating\ud environments. Our model projections suggest that a near complete feminization of hatchling output into this\ud population will occur by 2070 under an extreme scenario of climate change (A1T emission scenario). Importantly, we found that some nesting grounds will still produce male hatchlings, under the most extreme scenario of climate change, this finding differs from predictions for other locations. Information from this study provides a better understanding of possible future changes in hatching success and sex ratios at each site and identifies important male producing regions. This allowed us to suggest strategies that can be used at a local scale to offset some of the impacts of warmer incubating temperatures to sea turtles

Impacts of climate change on the largest green turtle population in the world: the nGBR green turtle population

[Extract] Sea turtles are vulnerable to aspects of climate change because they have life history, physiological attributes and behaviour that make them extremely sensitive to environmental changes (Hamann et al., 2007; Hawkes et al., 2009; Poloczanska et al., 2009). Arguably, the more detectable impacts of climate change to sea turtles will occur during their terrestrial reproductive phase (egg laying, egg incubation and hatchling success phase) since there are clear, and relatively straightforward, effects of increased temperature, sea level rise and cyclonic activity on sea turtle nesting sites and reproductive output (Hawkes et al., 2009; Fuentes et al., 2010a; Witt et al., 2010)

Mating system, multiple paternity and effective population size in the endemic flatback turtle (Natator depressus) in Australia

In recent years, genetic studies have been used to investigate mating systems of marine turtles, but to date no such research has been conducted on the flatback turtle (Natator depressus). This study investigates paternity of flatback turtle clutches at two rookeries in Queensland, Australia; Peak Island (Keppel Bay), and Mon Repos (Bundaberg). In the 2004–2005 nesting season, tissue samples were taken from either single or multiple clutches (n = 16) of nesting females (n = 8) representing a sampling effort ranging from 25% to 50% offspring per nest. Determination of the extent of multiple paternity was done using a comparative approach that included initial inferences based on observed alleles, Chi-square tests for deviations from Mendelian expectations, and three software programs (PARENTAGE1.0, GERUD2.0 and MER3.0). Results varied depending on the approach, but by calculating a consensus value of the output from these different methods, the null hypothesis of single paternity could be rejected in at least 11 of the 16 clutches (69%). Multiple paternity was thus observed in the clutches of six of nine females (67%), with two or three fathers being the most likely outcome. Analyses of successive clutches illustrated that paternal contribution to clutch fertilization can vary through time, as observed for two females. This first evidence regarding the mating system of flatback turtles indicates that multiple paternity is common in this species and that the observed frequency of multiple paternity is among the higher values reported in marine turtle species. Application of these results to estimates of effective population size (N e) suggests that population size may have been relatively stable over long periods. Continued monitoring of population dynamics is recommended to ensure that future changes in the east coast can be detected