Mercury levels, reproduction, and hematology in western grebes from three California Lakes, USA

Abstract

AbstractTwenty‐three healthy adult western and Clark's grebes (Aechmophorus occidentalis and Aechmophorus clarkii) were collected at three study sites in California, USA, in 1992: Clear Lake, Lake County; Eagle Lake, Lassen County; and Tule Lake, Siskiyou County. Liver, kidney, breast muscle, and brain were analyzed for total mercury (Hg) concentration (ppm wet weight), and blood was analyzed for various blood parameters. Clear Lake birds (n = 13) had greater Hg concentrations in kidney, breast muscle, and brain than birds from the other two lakes (p < 0.05), whereas liver concentrations were not statistically different (p > 0.05). Average concentrations for Clear Lake birds were 2.74 ppm for liver, 2.06 ppm for kidney, 1.06 ppm for breast muscle, and 0.28 ppm for brain. The tissue levels of kidney, breast muscle, and brain at the other two study sites were one half the levels found at Clear Lake. These mean tissue levels were near, but below, those known to cause adverse effects. When data from all sites were merged, kidney, breast muscle, and brain concentrations are positively correlated to each other (p < 0.05). Liver concentrations were not correlated to any other value. Brain Hg concentrations were also negatively correlated to blood potassium and blood phosphorus levels (n = 11, p < 0.05). Kidney Hg levels were positively correlated to percent blood heterophils and negatively correlated to percent eosinophils (n = 13, p < 0.05), suggesting that mercury levels might be affecting immune function. These biomarkers could not be related to any obvious ecological effects.