Abstract
Female birds whose bodies contain environmental contaminants produce eggs with shells that are likewise contaminated, making bird eggshells appropriate indicators for monitoring environmental toxins. Common contaminants include organic mercury compounds, especially methylmercury, which are known to bioaccumulate and biomagnify in the food chain. Black storks (Ciconia nigra) predominantly consume fish and are thus at risk for high mercury intake. In this study, we used eggshells of black storks as a proxy to reconstruct the concentration levels and distribution of mercury, a well-known toxic element, in various parts of Latvia. Preliminary analyses have shown that deposition levels of mercury vary in different parts of the eggshell. Specifically, the shell and shell membrane differ in their level of mercury contamination by an average factor of nine; therefore, we measured the mercury content in these components separately whenever possible. We analysed 34 eggshell samples from nesting sites in Latvia using an atomic absorption spectrometer with Zeeman correction Lumex RA-915M and its attachment for pyrolytic combustion. We found that mercury concentrations varied from 5 to 22 ng/g in eggshells and from 42 to 293 ng/g in shell membranes. We discuss possible contamination sources and reasons behind this disparity.
Highlights
Mercury is one of the most toxic elements affecting living organisms and the environment
Afterwards, methylmercury enters the food chain through small organisms, such as algae and plankton, and it bioaccumulates and biomagnifies, rapidly increasing its concentration [4]. Because of these biogeochemical processes, even moderate mercury concentration levels in the surrounding environment can result in serious toxicity for organisms that are positioned higher on the food chain, such as large fish, fish-eating birds, and humans [3], [5]
Inner membranes contained more mercury, with the lowest concentration we recorded at 42 ng/g, but results varied among nesting sites
Summary
Mercury is one of the most toxic elements affecting living organisms and the environment. Afterwards, methylmercury enters the food chain through small organisms, such as algae and plankton, and it bioaccumulates and biomagnifies, rapidly increasing its concentration [4]. Because of these biogeochemical processes, even moderate mercury concentration levels in the surrounding environment can result in serious toxicity for organisms that are positioned higher on the food chain, such as large fish, fish-eating birds, and humans [3], [5]. Birds’ intestines absorb only a small percentage of inorganic mercury but almost all organic mercury, and most mercury in fish is methylmercury [6]
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