Ms. Sepulveda et al., CONCENTRATIONS OF MERCURY AND SELENIUM IN TISSUES OF DOUBLE-CRESTED CORMORANTS (PHALACROCORAX-AURITUS) FROM SOUTHERN FLORIDA, Colonial waterbirds, 21(1), 1998, pp. 35-42
Tissues from 99 Double-crested Cormorants (Phalacrocorax auritus) coll
ected between 1994 and 1997 from southern Florida, were analyzed for c
oncentrations of mercury and selenium. These concentrations were corre
lated with each other, including concentrations of mercury and seleniu
m in liver. Mercury and selenium in liver increased from a mean of 15
and 8 mg kg(-1) wet weight (ww) in the fall, winter and spring to a me
an of 41 and 13 mg kg(-1) ww in the summer, respectively. Similarly, c
oncentrations of mercury in brain increased from a mean of 1.3 mg kg(-
1) ww in the fall, winter and spring to a mean of 2.2 mg kg(-1) ww in
the summer. Concentrations of selenium in liver increased with age. Se
x, physical condition, year, and geographic location of recovery had n
o significant effect on mercury and selenium concentrations. Between 1
2 and 15% of the cormorants studied had hepatic selenium and mercury c
oncentrations of over 20 and 50 mg kg(-1) ww, respectively (considered
lethal in some avian species). Liver selenium concentrations of over
3 mg kg(-1) ww and brain mercury concentrations above 2 mg kg(-1) ww (
related to reproductive failure in adult loons and mallards) were obse
rved in 57% and 32% of the cormorants studied, respectively These resu
lts could mean that Double-crested Cormorants in southern Florida migh
t be at risk of mercury and selenium poisoning.