Mercury content in the baleen plates of rorqual whales

Mercury is a persistent environmental contaminant posing significant risks to wildlife health due to its propensity for bioaccumulation in organismal tissues. This study investigated total mercury concentrations in the baleen plates of rorqual whales (Family Balaenopteridae), specifically the Fin whale (Balaenoptera physalus), Blue whale (B. musculus), and Rice’s whale (B. ricei). Archived baleen samples were sourced from the Smithsonian’s National Museum of Natural History and analyzed for total mercury (Hg) content (ppm dry weight) using atomic absorption spectroscopy. Male Fin and Blue whales from the Antarctic, South Pacific region (1947-1948), with body lengths ranging from 21 to 24 m, exhibited mean Hg concentrations of 0.19 ± 0.05 ppm and 0.14 ± 0.01 ppm, respectively (n = 2 per species). In contrast, male and female Rice’s whales from the Mid-Atlantic and Gulf of Mexico (1923-2009), with ranging from 5 to 13 m in length, demonstrated higher Hg burdens compared to their congeners, averaging 0.80 ± 0.66 ppm (n = 8). Rice’s whales showed evidence of Hg bioaccumulation, as indicated by a positive relationship between Hg concentration and body size. Notably, size-standardized Hg levels in the 1923 Rice’s whale sample was substantially higher compared to those from later years (1923 = 1.99 ppm; 1974-2009 = 0.39 ppm). The observed variations in Hg contamination across whale species likely reflect inter-specific differences in geographic location, migratory behavior, habitat use, and feeding ecology. Additionally, the reduction in Hg concentrations in Rice’s whales post-1970 may be linked to global pollution control measures