Mercury and its compounds are toxic - they can cause different health problems for humans and animals and pollute the environment. Methylmercury is one of the most harmful mercury compounds. It is characterized by accumulation in the food chains as a result of bioaccumulation and biomagnification processes, and low concentrations of mercury may accumulate to a health-threatening level.
Unlike white storks, which are omnivorous, black storks are fish-eaters, and their menu is mostly composed of small freshwater fish. So they are at higher risk of consuming mercury, researchers explain.
In the study, samples were collected in more than 150 nests from the entire territory of Latvia over several years. A total of more than 1,000 samples have been collected.
The results of the study show that mercury is found in both eggshells and membranes and feces. The lowest concentrations were obtained in eggshells, where they averaged between five and 30 nanograms per gram.
By contrast, membranes separated from shells had concentrations between nine and 11 times higher on average, reaching several hundred nanograms per gram.
In feces, the mean mercury concentration varied around 100 nanograms per gram. The nearest limit value laid down in the Cabinet of Ministers Regulation on the permissible concentration of mercury in biota shall be approximately 100 nanograms per gram.
Study co-author, researcher Anda Ābola of the LU Institute of Atomic Physics and Spectroscopy, says there are differences in concentrations between different nests and depending on the year the samples were collected.
The researchers are currently continuing an in-depth analysis of data to assess the prevalence of mercury pollution in the territory of Latvia, as well as the potential impact of the determined mercury concentrations on the health of black storks.
Black storks in Latvia are protected.
