Dermochelys coriacea

Abstract
Seven species of turtles are present in a wide range of areas across the earth. The species that use 
the beaches of Sint Maarten as nesting grounds are the Green sea turtle (Chelonia mydas), 
Leatherback sea turtle (Dermochelys coriacea) and Hawksbill sea turtle (Eretmochelys imbricata). 
Even with their protected status, populations are declining rapidly. This has a negative impact since 
sea turtles have significant ecological, economic and social values. To prevent populations from 
declining further, research is needed to create proper conservation strategies. This research focuses 
on different factors that could hinder nesting activity and how they influence sea turtles on Sint 
Maarten. These potential factors were researched in the literature and were determined to be 
artificial lighting, dune scarps, coastal development, slope, distance from high tide line to beach line, 
sargassum and human disturbances. Using a Spearman correlation test in SPSS, the correlation 
between the presence of these factors and the total nesting activity that takes place was tested. The 
test showed a moderate negative relation which was statistically significant 
(rs = -.681, p = .044). This means that the number of factors that are present at each beach influence 
the total nesting activity to some extent, but no strong correlation is present. These results indicate 
that if more factors which could hinder the sea turtle nesting activity are present, less sea turtle 
nesting activities take place on that beach on St. Maarten.

Abstract:

This study presents a comprehensive genetic analysis of stock structure for leatherback turtles (Dermochelys coriacea), combining 17 microsatellite loci and 763 bp of the mtDNA control region. Recently discovered eastern Atlantic nesting populations of this critically endangered species were absent in a previous survey that found little ocean-wide mtDNA variation. We added rookeries in West Africa and Brazil and generated longer sequences for previously analyzed samples. A total of 1,417 individuals were sampled from nine nesting sites in the Atlantic and SW Indian Ocean. We detected additional mtDNA variation with the longer sequences, identifying ten polymorphic sites that resolved a total of ten haplotypes, including three new variants of haplotypes previously described by shorter sequences. Population differentiation was substantial between all but two adjacent rookery pairs, and FST values ranged from 0.034 to 0.676 and 0.004 to 0.205 for mtDNA and microsatellite data respectively, suggesting that male-mediated gene flow is not as widespread as previously assumed. We detected weak (FST = 0.008 and 0.006) but significant differentiation with microsatellites between the two population pairs that were indistinguishable with mtDNA data. POWSIM analysis showed that our mtDNA marker had very low statistical power to detect weak structure (FST \ 0.005), while our microsatellite marker array had high power. We conclude that the weak differentiation detected with microsatellites reflects a fine scale level of demographic independence that warrants recognition, and that all nine of the nesting colonies should be considered as demographically independent populations for conservation. Our findings illustrate the importance of evaluating the power of specific genetic markers to detect structure in order to correctly identify the appropriate population units to conserve. 

Abstract:

Ingestion of marine debris can have lethal and sublethal effects on sea turtles and other wildlife. Although researchers have reported on ingestion of anthropogenic debris by marine turtles and implied inci- dences of debris ingestion have increased over time, there has not been a global synthesis of the phenomenon since 1985. Thus, we analyzed 37 studies published from 1985 to 2012 that report on data collected from before 1900 through 2011. Specifically, we investigated whether ingestion prevalence has changed over time, what types of debris are most commonly ingested, the geographic distribution of debris ingestion by marine turtles relative to global debris distribution, and which species and life-history stages are most likely to ingest debris. The probability of green (Chelonia mydas) and leatherback turtles (Dermochelys coriacea) ingesting debris increased significantly over time, and plastic was the most commonly ingested debris. Turtles in nearly all regions studied ingest debris, but the probability of ingestion was not related to modeled debris densities. Furthermore, smaller, oceanic-stage turtles were more likely to ingest debris than coastal foragers, whereas carnivorous species were less likely to ingest debris than herbivores or gelatinovores. Our results indicate oceanic leatherback turtles and green turtles are at the greatest risk of both lethal and sublethal effects from ingested marine debris. To reduce this risk, anthropogenic debris must be managed at a global level.