Mercury and Methylmercury Stable Isotope Measurements in Giant Petrels

Methylmercury (MeHg) and total mercury (HgT) stable isotope measurements were made by the USGS Mercury Research Lab (MRL) in different organs on the Giant Petrels (Macronectes spp.) to examine internal mercury cycling in these seabirds. These data were collected as a compliment to x-ray spectroscopy measurements made by the University of Grenoble, France. The tissues and feathers of the southern giant petrels exhibit large variability in mercury-202 isotope values (?202HgT), which are typically used to ascertain Hg sources in the environment. These values follow a pattern across all individuals based on tissue type: feathers (?202HgT = 2.74 � 0.16?, n =5, mean � standard deviation) greater than brain (?202HgT = 1.09 � 0.77?, n = 3) greater than liver (?202HgT = 0.04 � 0.11?, n = 5) greater than kidneys (?202HgT= 0.01 � 0.25?, n = 5) greater than muscle (?202HgT = -0.80 � 0.23?, n = 5). The ?202HgT for liver tissues are within the range of literature data for seabirds (?0.64? less than ?202Hgl less than 0.68?), whereas ?202Hg for feathers are modestly higher than those measured previously for seabirds (1.10? less than ?202Hgf less than 2.35?). Notably, muscle tissues exhibit considerably lower ?202HgT values than liver tissues (on average 0.84?), counter to observations to other birds and mammals, and were as much as ~?4? enriched in light isotopes compared to feathers. The ?202MeHg values, associated with just the MeHg contents within the tissues, for organs and feathers were constrained between 0.90 and 3.05 ? (n =9).