Affects of Climate Change on Loggerhead Turtles
Temperature-dependent sex-Determination
Before hatching, loggerheads undergo a temperature-dependent process that determines their sex based on a 1 to 4 degree Celsius temperature fluctuation up or down from the pivotal temperature of 29 degrees Celsius (Wibbels 2002). Some environments have already become hostile to breeding male loggerheads and if global temperatures continue to rise, nesting beaches will fall outside of the range of temperatures needed to produce any male hatchlings (Chu et al. 2008). This could effectively decimate the male loggerhead population and eliminate any future chances of mating.
Figure 3: The point on the graph shows the pivotal temperature at which percentage of one sex will be greater than the other sex in a single clutch. In the case of Loggerheads, this temperature is 29 degrees Celsius. The shaded box shows the one to four degree Celsius range in which both male and female loggerheads are still produced, but with a dominating ratio towards one sex when not at the pivotal point. Outside the shaded region represents the temperatures at which 100% male or female hatchlings are produced.
Figure 3 image from <http://www.seaturtle.org/mtn/archives/mtn128/MTN128p8.gif>.
Increasing Storm Intensity & Rising Sea Levels
Climate Change leads to increases in intensity and durations of storms and causes fluctuations in widespread atmospheric patterns that directly affect ocean ecosystems (Limpus & Reed 1985). The increase in frequency of these storms, along with rising sea levels, will impact the turtles’ ability to find nests and can potentially drown or wash away nests altogether (Foley et al. 2006). For loggerheads foraging in shallow waters, lengthy storm surges can cause stress, injury, and even death (Limpus & Reed 1985).
Ocean Currents
There has been a shift towards the poles of major sub-tropical ocean currents due to changing patterns in the periodic atmospheric event of El Nino Southern Oscillation (Poloczanska et al. 2009). There is evidence that this shift has affected loggerheads’ migratory routes (McClellan & Reed 2007). This could potentially affect their ability to return to nesting locations and the availability of food at different latitudes (Hawkes et al. 2007).
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Figure 4: The life cycle of the Loggerhead turtle and activity at different stages of life.
Image found at <http://stpetebeachtoday.com/Articles_Home/ArticleRead.php?ArtID=CC100903>.
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