Michael W. Meyer Ronald Rossmann Annette Gendron-Fitzpatrick Brian R. Gray Kevin P. Kenow 2011 <p><span>To determine the level of in ovo methylmercury (MeHg) exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks, we conducted a field study in which we injected eggs with various doses of MeHg on day 4 of incubation. Eggs were collected following about 23&nbsp;days of natural incubation and artificially incubated to observe hatching. Reduced embryo survival was evident in eggs injected at a rate of ≥1.3&nbsp;μg Hg/g wet-mass. When maternally deposited Hg and injected Hg were considered together, the median lethal concentration of Hg (LC</span>₅₀<span>) was estimated to be 1.78&nbsp;μg Hg/g wet-mass. Organ mass patterns from eggs of chicks injected at a rate of 2.9&nbsp;μg Hg/g differed from that of controls and chicks from the 0.5&nbsp;μg Hg/g treatment, largely related to a negative relation between yolk sac mass and egg mercury concentration. Chicks from eggs in the 2.9&nbsp;μg Hg/g treatment were also less responsive to a frightening stimulus than controls and chicks from the 0.5&nbsp;μg Hg/g treatment. We also found that the length of incubation period increased with increasing egg mercury concentration. Tissue Hg concentrations were strongly associated (</span><i>r</i><span>&nbsp;</span>²<span>&nbsp;≥&nbsp;0.80) with egg Hg concentration.</span></p> application/pdf 10.1007/s10646-011-0743-9 en Springer Effects of injected methylmercury on the hatching of common loon (Gavia immer) eggs article