Article Review: Mercury and Selenium Concentrations in Leatherbacks

Why are Hatching and Emergence Success Low? Mercury and Selenium Concentrations in Nesting Leatherback Sea Turtles (Dermochelys coriacea) and their young in Florida.

Authors: Justin Perrault, Jeanette Wyneken, Larry Thompson, Chris Johnson, Debra Miller

 

            The very last day of class our lecture consisted of focusing on conservation efforts and why amphibians and reptiles are seeing dramatic population declines. When reflecting on the past semester of herpetology I remembered one of my favorite articles the class read as part of an assignment and it was about the leatherback sea turtles (Dermochelys coriacea). These turtles are extraordinary for one, because of their large size and two, their endothermic abilities to travel from subpolar regions in the water to tropical regions. They are even placed within their own family because of their uniqueness. The leatherback sea turtle is currently listed as federally endangered. There could be many reasons for this explanation but one article explains an interesting possibility as to why scientist are seeing a huge decline in the leatherback sea turtle population.

            The leatherback sea turtle hatchlings have consistently been shown to have low success rate. Part of this reason is because of predation and when some of the eggs are washed away from the tides. Another reason may be due to the amount of mercury (Hg) and selenium (Se) in nesting female leatherbacks and hatchlings. Selenium and mercury are stored in the liver and when selenium deficiency is low then the concentration of mercury should be high. Selenium has beneficial uses for the animal such as it acts as an antioxidant to name one. However, when the levels of selenium are high in the liver it can produce harmful effects such as abnormalities, reduced reproductive fitness, and death. These elements are ingested by food and water intake. Recently the mercury levels in the oceans have been found extremely high due to burning of fossil fuels. It can be traced in animals from the top predators to the bottom of the food chain. It has recently been studied that mercury ingested by a pregnant human can lead to birth abnormalities. This is the first study that documents mercury and selenium concentration in a hatchling sea turtle and the first to correlate both hatchling and maternal in relation to reproductive success.    

            In Juno and Jupiter beach Florida during the 2007 and 2008 reproduction season the blood of nesting leatherback females were taken shortly after oviposition. Most of these females the approached the beach have been tagged and if they were not tagged then the research facility tagged them. After the eggs were laid the nests were then monitored on the beach. The hatchlings were collected by a cage placed over the nest on the day they were expected to emerge. Once it was time for the hatchlings to emerge from the nests 10 normal hatchlings were selected and their blood was taken for data and then released. Then 5 dead turtles were selected from the nests for data analysis. The blood samples were then tested for the amount of mercury and selenium in the hatchlings and adult females. A series of laboratory tests and computer analysis tests were constructed.  

            The main goals of this experiment were to determine how selenium amounts affect leatherback turtle nest success. Also how mercury and selenium in a hatchling’s blood, yolk, and liver, are correlated with the maternal blood concentrations. In the results tt was found that leatherback sea turtles have concentrations of selenium from 0.39-21.27 ppm which is mainly due to the diet. When comparing the results to other research it was concluded that the amount of mercury depended on the location and from food and water. The ratio of mercury to selenium was positively correlated to the hatchling and emergence success. Part of the egg morphology, the albumen globs may help decrease toxins via elimination. What this means is that protection of selenium against mercury actually allows for live turtles to survive by hatching and emerging from the nests. Eventually, this can potentially cause an increase in the leatherback sea turtle population.    

          This past semester our herpetology class learned about turtle reproduction and about how the sexes of turtles are determined. This article demonstrates how other factors may come into play on why the reproductive success of the leatherback sea turtle is at risk. It takes what we already know about sea turtle reproduction to a whole other level. It ties together how pollution from the burning of fossil fuels affects the leatherback sea turtle population. I found this article interesting because it helps raise other questions about conservation like how can we save the leatherback sea turtle population from being federally endangered. This article grabbed my attention because of my recent knowledge about herpetology and my interest in marine ecology and conservation. Hopefully this article will lead to answers about conserving the sea turtle.   

 

Works Cited:

Justin Perrault, Jeanette Wyneken, Larry Thompson, Chris Johnson, Debra Miller. 2011. Why are Hatching and Emergence Success Low? Mercury and Selenium Concentrations in Nesting Leatherback Sea Turtles (Dermochelys coriacea) and their young in Florida. Marine Pollution Bulletin 62 (1671-1682).

http://www.sciencedirect.com.nuncio.cofc.edu/science/article/pii/S0025326X1100333X

Chelsea Taylor
College of Charleston