Mercury and selenium concentrations in stranded bottlenose dolphins from the Indian River Lagoon system, Florida

Mercury is a toxic metallic element that is known to bioaccumulate in many marine organisms. Mercury concentrations are routinely evaluated in Indian River Lagoon (IRL) fish, however, there are no published reports of these concentrations for IRL bottlenose dolphins, Tursiops truncatus (Montagu, 1821). Muscle (n = 30) and liver (n = 19) samples from stranded IRL dolphins were collected and analyzed for total mercury and selenium. Total mercury concentrations in liver samples ranged from 0.42 to 240 ppm wet weight (ww) (mean = 73.01 ppm) and concentrations in muscle samples ranged from 0.26 to 47 ppm ww (mean = 5.68 ppm). Mercury concentrations were not significantly different between mates and females for both tissue types. Selenium concentrations ranged from 1.20 to 90.70 ppm ww (mean = 29.81 ppm) in liver tissue and 0.75 to 16.10 ppm ww (mean = 1.92 ppm) in muscle tissue. Selenium concentrations were positively correlated with mercury in both tissue types. Age and total length were good predictors for mercury concentrations in both tissue types. Future studies are needed to determine what effect mercury may have on the overall health of IRL dolphins.