59 - Analysis of Mercury Concentration Measurements in the Faeces of Black Storks

"Use of the wildlife as bio-indicators is a common practice when assessing the environmental pollution. Various types of samples can be used for monitoring, depending on chosen pollutant and living organism species. For birds those are, for example, blood, feathers, faeces, eggs and eggshells.

Mercury is well known for its ability bio-accumulate and bio-magnify through the food chain, resulting in possibly harmful concentrations. It is especially true for aquatic ecosystems, where most of the methylation processes happen. Black storks (Ciconia nigra) are piscivorous birds and as such have an elevated risk for higher mercury intake than non-piscivorous birds.

In this work we analysed faecal samples of black storks from various nesting sites in Latvia. Samples were collected between years 2019 and 2021, twice a year - in the spring and in the summer. It is possible to differentiate between droppings of parents (in the spring, before hatching) and chicks (in the summer), as couple weeks after hatching adult birds only return to the nest to feed the chicks, but do not defecate near it.

Mercury concentration measurements were performed using atomic absorption spectrometer Lumex RA-915M and its attachment for pyrolytic combustion.

Results showed that faeces contain some amount of mercury, concentrations varying between 10 - 522 ng/g, depending on the season of collection and the location of the nest.

This work was supported by the Latvian Council of Science No. lzp-2020/1-0005."

Authors: Anda Abola, Maris Strazds, Zanda Brike, Rita Veilande, Kristiana Rancane