|Abstract Title:||Internal Dynamics of Mercury in the Antarctic Penguin, the Potential Bioindicator for Mercury at Remote Regions|
|Presenter Name:||Saebom Jung|
|Company/Institution:||Pohang University of Science and Technology|
|Session:||Mercury in Polar Ecosystems|
|Day and Session:||Tuesday 26th July - Session Two|
|Start Time:||10:00 UTC|
Abstract Information :
Since implementing the Minamata convention, a growing number of studies have been characterizing sources and internal processes governing the mercury (Hg) level and its burden in various types of biota, including terrestrial insects, birds, mammals, and freshwater fish. While bioindicator species for Hg in freshwater and terrestrial environments are well characterized, those in remote environments such as the Antarctic is yet to be investigated. Here, we measured concentration and stable isotope ratios of Hg in five different tissues in Adelie and Emperor penguins from four regions in the Antarctic. We chose penguins as a potential bioindicator for mercury because of their high trophic positions and long lifespan. The tissue-specific comparison of mercury isotopes revealed consistent ?199Hg across the tissues, indicating the absence of internal process-induced variations in ?199Hg. The ?202Hg of the tissues showed significant positive relationships with the fraction of methylmercury (% MeHg) in all penguins, with the muscle and liver exhibiting the highest and lowest ?202Hg, respectively. We attribute the low ?202Hg in the liver to the hepatic demethylation, resulting in a lower ?202Hg in the product inorganic mercury relative to MeHg subject to redistribution to the muscle. Given the absence of ?199Hg changes via internal processes, we used the muscle ?199Hg to explain the interspecific difference in the Hg sources in penguins. The Emperor penguins displayed measurably lower ?199Hg (1.21 to 1.31?) compared to Adelie penguins (1.31 to 1.66?), which was attributed to their deeper diving depths and the consumption of mesopelagic prey. Adelie penguins feeding primarily in the surface water consume epipelagic prey (i.e., plankton, krill), which have bioaccumulated MeHg that has undergone extensive photo-degradation. Our study is essential in determining the appropriate isotopic indicator and penguin tissues for mercury source monitoring in the remote Antarctic and distinguishing ecological characteristics between two species in penguins.