1. bookTom 48 (2019): Zeszyt 2 (June 2019)
Informacje o czasopiśmie
License
Format
Czasopismo
eISSN
1897-3191
Pierwsze wydanie
23 Feb 2007
Częstotliwość wydawania
4 razy w roku
Języki
Angielski
Otwarty dostęp

Evaluation of claws as an alternative route of mercury elimination from the herring gull (Larus argentatus)

Data publikacji: 03 Jun 2019
Tom & Zeszyt: Tom 48 (2019) - Zeszyt 2 (June 2019)
Zakres stron: 165 - 173
Otrzymano: 09 Jul 2018
Przyjęty: 19 Sep 2018
Informacje o czasopiśmie
License
Format
Czasopismo
eISSN
1897-3191
Pierwsze wydanie
23 Feb 2007
Częstotliwość wydawania
4 razy w roku
Języki
Angielski
Introduction

Mercury enters the environment both from natural (volcanic activity, forest fires, waterbody movement, rock weathering, biological processes) and anthropogenic sources (mining operations, industrial processes, combustion of fossil fuels, especially coal, cement production, and incineration of medical, chemical, and municipal wastes) (Poulin & Gibb 2008). Once introduced into the atmosphere, mercury is transported over long distances so that it can be deposited in places far from emission sources (WHO/IPCS 1990). Mercury enters the sea mainly in the form of inorganic Hg2+or as Hg°, from where it is absorbed by aquatic microorganisms and can be transformed into the most toxic organic form, i.e. methylmercury – CH3Hg, also written as MeHg (Fitzgerald et al. 2007; Blum et al. 2013). As a consequence, it is incorporated into the trophic chain (WHO/IPCS 1990; Scheuhammeret al. 2007). Methylmercury is classified as an endocrine-active compound, which means that it can affect the hormonal system and lead to harmful developmental, reproductive and neurological changes (Georgescu et al. 2011).

The structural characteristics of the Baltic Sea and the fact that it is located in a highly urbanized and densely populated area of Europe make it particularly exposed to anthropogenic pollution. The former widespread use of mercury in industry, spanning over a century, and the fact that the reduction in mercury emissions did not occur until the end of the 20th century (HELCOM 2010) means that there are still areas (landfills, areas of industrial plants with former Hg usage) where Hg pollution is common (Bełdowska 2016). Mercury is supplied to the coastal zone of the Gulf of Gdansk mainly via rivers (Saniewska et al. 2010) where, as in other estuaries, it mostly accumulates (Cossa & Martin, 1991). Only a small part of the mercury transported by rivers reaches the open sea.

Seabirds, being at the top of the trophic chain, are good indicators of pollution in coastal areas (Savinov et al. 2003). The herring gull (Larus argentatus, Pontopiddan, 1763) is a migratory species widespread in Northern Europe. Mature birds breeding on the Polish coast may be sedentary. The herring gull is also one of the largest birds and the most numerous species found on the Polish coast in wintertime (Meissner et al. 2007). The birds use both natural and anthropogenic food sources, often accompanying fishing boats, which provide them with an easy way to obtain fish waste. Their diet also includes fish, invertebrates, shellfish, small amphibians, as well as eggs and chicks of other gulls. In winter, they make more intensive use of landfills located near major cities. In Poland, the herring gull is a partially protected species (Dz.U. 2016, item 2183).

The main route of exposure of birds to mercury is via food intake (Khale & Becker 1999), which introduces this chemical element into the bird body in its most toxic form – methylmercury. An additional source of mercury is inhalation, which provides the body with the inorganic form (Falkowska et al. 2017). The capacity of mercury to accumulate and magnify results in its increased concentrations in the tissues and organs of seabirds, which may be several times higher compared to other parts of the coastal zone ecosystem. Kalisinska & Dziubak (2007) indicate that high levels of mercury in the central nervous system may disturb the motor coordination and kinesthesia of birds. The summary of toxicity benchmarks for the methylmercury exposure effects on birds presented by Ackerman et al. (2016) shows that bird reproduction is particularly sensitive to mercury toxicity with reduced reproductive success, reduced egg hatchability and offspring survival, all mentioned among many documented deleterious effects.

Together with blood, organic mercury is transported to the liver, where it can be demethylated and then distributed throughout the body (Burger & Gochfeld 2002; Burgess et al. 2013). Birds, however, have several mechanisms through which they can get rid of mercury present in their bodies. Although only small amounts of mercury are excreted with guano, this route leads to its faster reintroduction into the environment (Yin et al. 2008). The most effective removal of mercury occurs during molting, while females may additionally eliminate the accumulated mercury through eggs (Becker 1992).

Herring gulls in the region of the southern Baltic have already been the subject of research on the distribution and elimination of mercury (Szumiło et al. 2013; Szumiło-Pilarska et al. 2016; Falkowska et al. 2017; Szumiło-Pilarska et al. 2017) and of organic pollutants contained in different organs (Falkowska et al. 2016; Reindl et al. 2015). In the majority of specimens examined, the highest concentrations of mercury were observed in the liver and kidneys followed by lungs, muscles and brain. Among the examined tissues, the intestines were characterized by the lowest concentrations of mercury (Szumiło-Pilarska et al. 2016; Falkowska et al. 2017). Previous research also suggested that adult herring gulls may be potential sentinels of environmental contamination with mercury on a local and regional scale, based on blood and developing feather tests. Newly emerging feathers can also indicate the effectiveness of demethylation in relation to fully developed feathers (Szumiło-Pilarska et al. 2017).

Since the incorporation of mercury into the feathers is undoubtedly recognized as the most effective way of eliminating mercury from the body (Braune & Gaskin 1987; Monteiro & Furness 1995), the authors decided to assess the transport and incorporation of toxic mercury into birds' claws, which, like feathers, are keratinous structures (Hahn et al. 2014). Birds' claws are heavily keratinized epidermal structures, which vary depending on how they are used and the substrate on which birds live (Stettenheim 2000). The toe claw, which is present in every bird species, is composed of a dorsal plate that curves downward on the tip and sides and a ventral plate that fills the space between the sides underneath (Lucas & Stettenheim 1972). The dorsal plate is harder and contains heavy deposits of beta-keratin and calcium salts (Stettenheim 2000). Unlike feathers, claws grow continuously (Lucas & Stettenheim 1972; Ethier et al. 2010). Furthermore, the growth is conical (not linear) – the outer layers are always older than the inner layers (Hahn et al. 2014).

The objective of the study was to assess individual differences in total mercury concentrations (HgTOT) in claws of herring gulls (Larus argentatus) in relation to age classes. Furthermore, the results of mercury concentrations in selected tissues, organs and feathers of the same individuals published in previous works were used to provide a broader interpretation of the presented results.

Materials and methods
Biological material for analysis

Claws were recovered from 49 dead herring gulls found around the Gulf of Gdansk: 27 birds were found in the area of the fishing port in Władysławowo (φ = 54°47'N, A = 18°25'E), 13 in the Mewia Łacha bird sanctuary (φ = 54°21'N, λ = 18°57'E) located in the Vistula estuary and nine within the Tri-city agglomeration. Samples were collected in 2010–2012. Stainless steel scissors were used to remove the top part of each bird's claw (Fig. 1).

Figure 1

Sampling of herring gull's claws (parts of claws used for the analysis were cut off at the position marked by the dotted line)

The age of each bird was determined on the basis of its plumage (Malling Olsen & Larsson 2004) and three age categories were distinguished: juvenile specimens (chicks and birds in their first plumage), immature specimens (in their second and third plumage) and mature birds (in the fourth and final plumage). Gender was determined on the basis of DNA using the method of polymerase chain reaction – PCR (Fridolfsson & Ellegren 1999). A total (taking into account age and gender) of 19 mature (12 females, 7 males), 17 immature (6 females, 11 males) and 13 juvenile birds (8 females, 5 males) were used in the analysis. All birds were subjected to a postmortem during which, if possible, we collected blood (as a blood clot from the heart), internal organs (breast muscle, heart, liver, kidney, brain, intestines, lungs) and feathers (outermost primary P10, innermost primary P1, rectrices, breast contour feathers and down, and if birds were in the molting period, also new breast contour feathers), which were the focus of the previous research (Szumiło-Pilarska et al. 2016; Szumiło-Pilarska et al. 2017; Falkowska et al. 2017). The cause of death remained unknown but the cachectic condition of each bird was assessed. It was found that 10% of the birds were emaciated, including one male with suspected peritonitis (Falkowska et al. 2016).

Prior to analysis, all claws were washed with 80% acetone in an ultrasonic bath, rinsed with Milli-Q water and dried at room temperature. The whole claws were used for analysis.

Chemical analysis – total mercury (HgTOT)

The total mercury concentrations (HgTOT) were assayed using atomic absorption spectrometry on an AMA-254 analyzer. Weighed amounts of birds' claws (about 0.0100 g) were placed in pre-combusted nickel boats. Each sample was assayed in three replicates and the final result represents an average of three analyses. An empty pre-combusted nickel boat was used as a blank sample (for each of the 10 measurements). The precision of the method was measured using certified standards: BCR414 prepared on the basis of plankton and BCR463 – based on tuna. The precision was 5%. The accuracy expressed as mercury recovery was established at 96.7%, while the limit of quantification (LOQ) amounted to 0.075 ng HgTOT g–1 d.w.

Statistical Analysis

Statistica 10 was used for the calculations and visualization of the results. The normality of the distribution among the studied variables was examined using the Shapiro-Wilk test. The analysis of the relationships between the variables was carried out based on the Spearman correlation (nonparametric data). To test the significance of differences, the non-parametric Wilcoxon signed rank test, the Kruskal-Wallis test and the U Mann-Whitney test were used. All statistical analyses were performed at a confidence level of 95%.

Results

The analysis of the results was carried out on an extended data set which, apart from the original mercury results for claws, included the results of total mercury content in the tissues, organs (Szumiło-Pilarska et al. 2016; Falkowska et al. 2017) and feathers (Szumiło-Pilarska et al. 2017) of the same specimens. The Wilcoxon signed rank test showed that the concentrations of mercury in the claws were statistically significantly different (p < 0.05) from all other variables, with the exception of innermost primary P1, rectrices and breast contour feathers (new). The average mercury concentration in the claws was almost twice as high as the concentrations in the most mercury-loaded organs (liver, kidneys). Extremely high concentrations of mercury in the claws (Table 1) were observed in a mature female found in Wladyslawowo in the winter of 2010. At the same time, the maximum concentration values were also found in the brain and heart of that specimen, and one of the two extreme values was assayed in rectrices (6310.9 ng HgTOT g–1).

Statistical characteristics of mercury concentrations (ng HgTOT g–1 d.w.) assayed in claws, tissues and organs of herring gulls found around the Gulf of Gdańsk in 2010–2012

group n Md min.–max () noutlier/nextreme RNG
claws 49 869.2 127.2–5341.5 3/1 min.–2654.4
outermost primary P101 44 743.0 40.1–6989.5 1/1 min.–2689.9
innermost primary P11 40 1330.6 79.0–9186.8 1/0 min.–4739.6
breast contour feathers1 46 1437.7 131.3–8211.9 2/1 min.–4453.0
rectrices1 45 583.6 62.4–6355.6 0/2 min.–2908.0
down1 17 1138.6 605.3–4908.0 1/0 min.–4102.0
breast contour feathers (new)1 12 2153.8 399.5–4193.6 0/0 min.–max
liver2 48 546.9 58.1–1694.3 0/0 min.–max
kidney2,3 45 455.7 19.1–1882.6 1/0 min.–1872.3
lung2,3 46 311.8 31.4–1104.8 0/0 min.–max
muscle2 49 244.0 42.7–1076.7 0/0 min.–max
heart2 48 278.2 21.5–1043.8 0/0 min.–max
brain2,3 43 156.5 22.5–687.8 3/0 min.–459.9
blood2,3 41 434.4 15.4–1410.6 0/0 min.–max
intenstine3 37 208.2 18.5–933.2 2/0 min.–475.9

n –number of samples; Md– median value; min.–minimum; max–maximum; noutlier– number of outlier values; nextreme–number of extreme values; RNG–range without outlier and extreme values; the set of variables whose characteristics are presented in the table was created on the basis of previously published results: 1Szumilo-Pilarska et al. 2017; 2Szumiło-Pilarska et al. 2016; 3Falkowska et al. 2017

All the minimum concentrations of mercury in the individual variables were measured for juvenile specimens. One of them was also characterized by the lowest HgTOT concentrations in the brain, blood, down and cover feathers. The lowest concentration of mercury, on the other hand, was observed in a specimen that also had the lowest concentration of mercury in the liver, heart and lungs. Another juvenile specimen, worth mentioning, had mercury concentrations in all the collected types of feathers (outermost primary P10, breast contour feathers, rectrices) at levels above 6000 ng HgTOT g–1. In the case of outermost primary P10 and rectrices, they were the highest (extreme) values recorded for these types of feathers. It is worth noting that the bird was characterized by one of the lowest concentrations of mercury in the blood (65.9 ng HgTOT g–1), an order of magnitude lower than the mean value.

The Kruskal-Wallis test showed statistically significant differences (p = 0.0107) between the total mercury concentrations in bird claws in different age groups (Fig. 2). Multiple comparisons of mean ranks for all samples indicated that the immature age group corresponds to the test result, which is statistically significantly different from the juvenile

Figure 2

Mercury concentrations (ng HgTOT g–1 d.w.) assayed in claws of herring gulls found around the Gulf of Gdansk in 2010–2012 in different age categories

group. Since mature females can eliminate mercury during egg laying (Becker 1992), which may result in a reduced mercury body burden, the total mercury concentrations in claws of females and males were compared among the mature gulls. However, they did not show any statistically significant differences (U Mann-Whitney test; p = 0.33).

All relationships between the concentration of mercury in claws and the concentration of mercury in the tissues and internal organs were statistically significant (Table 2). In the case of feathers, statistically significant correlations were observed in outermost primary P10 and rectrices.

Spearman's correlation coefficients (R) between the total mercury concentration (ng HgTOT g-1 d.w.) in claws of herring gulls and the total mercury concentration (ng HgTOT g-1 d.w.) in their selected internal organs, tissues and feathers

selected variable n R P equation
outermost primary P10 44 0.38 0.010 claws = 0.2193 x outermost primary P10 + 1078.1857
innermost primary P1 40 n.s
breast contour feathers 46 0.35 0.016 claws = 0.1697 x breast contour feathers + 982.1230
rectrices 45 0.32 0.030 claws = 0.34228 x rectrices + 923.6664
down 17 n.s
breast contour feathers (new) 12 n.s
liver 48 0.39 0.006 claws = 0.4929 x liver + 980.5223
kidney 45 0.50 0.000 claws = 0.771 x kidney + 809.6370
lungs 46 0.45 0.002 claws = 1.5575 x lungs + 677.7302
muscle 49 0.34 0.018 claws = 1.0795 x muscle + 888.1018
heart 48 0.40 0.005 claws = 1.5484 x heart + 763.8899
brain 43 0.47 0.002 claws = 3.5917 x brain + 475.8652
blood 41 0.47 0.002 claws = 1.0740 x blood + 767.8458
intestines 37 0.48 0.003 claws = 2.6663 x intestines + 628.7789

n – number of samples; n.s. – non significant

Discussion

The wide range of total mercury concentrations in gull claws may be the result of a varying time of exposure to the studied xenobiotic. The life span of this species can reach up to 30 years (Kruszewicz 2011). Most of the birds reach sexual maturity in their fifth year of life, meaning that the oldest individuals in the mature category can be up to 6 times older than the youngest ones. Such a large difference in exposure time may be the reason for the largest spread of results among adults (Fig. 2). In addition to the narrow concentration range, juvenile specimens were characterized by the lowest average mercury concentration in the claws. This may be influenced by the rapid growth of birds in the first months of life resulting in reduced mercury concentrations in the tissues and internal organs (Falkowska et al. 2013; Grajewska et al. 2015). In the case of immature specimens, this rapid growth is no longer observed. In addition, this group is characterized by low age diversity.

It should be noticed that diet composition remains the most important factor affecting the intraspecific differences in mercury concentrations since food is the main intake path of mercury in seabirds (Scheuhammer et al. 2007). Kojadinovic et al. (2007) indicate that foraging habits may also be related to age. According to this research, mercury levels in adult birds were higher because they may have eaten larger, more contaminated prey compared to younger individuals. Furthermore, although herring gulls are known to be opportunistic predators and scavengers, they also feed on landfills (Meisner et al.

2007). Previous research on herring gulls (Falkowska et al. 2017) showed that non-breeding, immature birds are more often observed on the garbage dumps where they are exposed to lower levels of mercury. All the above considerations can be supported by results on the content of mercury in birds' claws, as it is known that they can gradually store the isotopic composition of the diet (Bearhop et al. 2003).

The mercury load on the internal organs of a bird is the result of the processes of uptake, transformation and elimination of mercury from the body (Monteiro & Furness 1995). An effective elimination of toxic substances is therefore crucial for maintaining the proper functioning of the body. When molting, birds have a unique opportunity to get rid of pollutants from the body without additional energy consumption. Each newly formed feather is supplied with various substances contained in the blood, including the most toxic methylmercury, which accounts for most of the mercury transported via blood. When the structure is fully developed, the blood supply vessels undergo a regression and thus the mercury stored in the feathers is retained there until the next molting period (Kojadinovic et al. 2007). It is estimated that feathers can incorporate from 70 to 93% of the mercury collected in the bird body (Braune & Gaskin 1987; Burger & Gochfeld 1997; Bond & Diamond 2009). This is possible because the main component of feathers is keratin, a substance containing -SH sulfhydryl groups, which have high affinity with methylmercury (Goede & De Bruin 1984).

Similarly to feathers, large amounts of mercury can be transported to the claws, which is evidenced by the average concentration of mercury in the claws. As in all types of feathers, these levels were higher than in the tissues and internal organs (Table 1).

The ease of obtaining feathers as a research material makes them a common indicator used to assess the state of the environment in which birds live (Braune & Gaskin 1987; Thompson et al. 1993; Monteriro & Furness 1995; Thompson et al. 1998; Furness & Camphuysen 1997; Stewart et al. 1997; Mallory et al. 2010). Although many studies (Braune & Gaskin 1987; Thompson et al. 1991; Zamani-Ahmadmahmoodi et al. 2014) indicate the existence of a correlation between mercury concentrations in feathers and internal organs, such correlations were not observed in herring gulls from the Gulf of Gdansk (Szumiło-Pilarska et al. 2017). This situation may be explained by the analysis of δ 515N stable isotopes in the muscles and feathers of the same specimens, proving that mercury comes from different sources in each of these structures (Szumiło-Pilaska et al. 2016). At the same time, it was shown that internal organs may be affected by mercury present in the inhaled air, which is more pertinent to birds staying in the coastal zone during the summer season (Falkowska et al. 2017).

The present work, however, has shown the existence of statistically significant correlations between all the examined internal organs and claws (Table 2). Mercury is transported to feathers only during the growth of feathers, which lasts for several weeks (Lewis & Furness 1991; Dauwe et al. 2003). Therefore, feathers reflect only the "temporary" state of the body and not the effect of prolonged exposure to the studied xenobiotic (Kojadinovic et al. 2007). The growth of claws is a continuous process (Lucas & Stettenheim 1972; Ethier et al. 2010), requiring a constant blood supply (Hoefer 2012). As a result, the total mercury concentrations in claws may correspond better to the mercury body burden represented by mercury levels in internal organs. However, it should be emphasized that the difficulty of obtaining claws means that they will never replace feathers in scientific research.

It is known that some birds can control mercury accumulation not only by excretion through molting but also through demethylation metabolism (Kim et al. 1996). Some studies have initiated a discussion on the process of organic mercury demethylation, which could take place in the brain and liver of herring gulls from the southern Baltic region (Szumiło-Pilarska et al. 2016). Falkowska et al. (2013) draw attention to the influence of the condition and age of birds on their ability to conduct demethylation. It was suggested that higher concentrations of mercury in feathers can occur as a result of increased mercury transportation to the feathers, due to negligible demethylation processes in the liver. It can be assumed that claws will reflect the effectiveness of demethylation in a similar way. The performed analyses appear to confirm these reports. The specimen (mature female) with the maximum concentration of mercury in the claws also had an extremely high concentration of mercury in the feathers. In addition, both values were similar to those described for a penguin from the zoo (Falkowska et al. 2013).

Conclusions

The wide range of total mercury concentrationsin the claws of herring gulls can be mainly due to the duration of exposure to the studied xenobiotic, although age-related feeding ecology cannot be ignored when interpreting the results. Claws, similarly to feathers, are corneous structures of the epidermis, built of keratin. The mercury incorporated into any of these structures does not pose a threat to a bird that is physically and chemically stable. However, when the bird dies, these structures will remain in the environment, and the mercury contained in them may be eventually transformed into more labile forms and thus return to circulation in the environment.

The study has shown that claws and feathers accumulate toxic mercury on a similar level, while other tissues and internal organs are characterized by lower HgTOT concentrations. It can therefore be concluded that the incorporation of mercury into the claws and feathers of birds is equally effective for both these structures. However, it should be remembered that although the load on feathers and claws can be considered similar, the contribution of claws in the elimination of mercury from the body is smaller compared to feathers. In addition, claws can also reflect demethylation processes, while providing a good picture of the mercury load on internal organs.

Figure 1

Sampling of herring gull's claws (parts of claws used for the analysis were cut off at the position marked by the dotted line)
Sampling of herring gull's claws (parts of claws used for the analysis were cut off at the position marked by the dotted line)

Figure 2

Mercury concentrations (ng HgTOT g–1 d.w.) assayed in claws of herring gulls found around the Gulf of Gdansk in 2010–2012 in different age categories
Mercury concentrations (ng HgTOT g–1 d.w.) assayed in claws of herring gulls found around the Gulf of Gdansk in 2010–2012 in different age categories

Statistical characteristics of mercury concentrations (ng HgTOT g–1 d.w.) assayed in claws, tissues and organs of herring gulls found around the Gulf of Gdańsk in 2010–2012

group n Md min.–max () noutlier/nextreme RNG
claws 49 869.2 127.2–5341.5 3/1 min.–2654.4
outermost primary P101 44 743.0 40.1–6989.5 1/1 min.–2689.9
innermost primary P11 40 1330.6 79.0–9186.8 1/0 min.–4739.6
breast contour feathers1 46 1437.7 131.3–8211.9 2/1 min.–4453.0
rectrices1 45 583.6 62.4–6355.6 0/2 min.–2908.0
down1 17 1138.6 605.3–4908.0 1/0 min.–4102.0
breast contour feathers (new)1 12 2153.8 399.5–4193.6 0/0 min.–max
liver2 48 546.9 58.1–1694.3 0/0 min.–max
kidney2,3 45 455.7 19.1–1882.6 1/0 min.–1872.3
lung2,3 46 311.8 31.4–1104.8 0/0 min.–max
muscle2 49 244.0 42.7–1076.7 0/0 min.–max
heart2 48 278.2 21.5–1043.8 0/0 min.–max
brain2,3 43 156.5 22.5–687.8 3/0 min.–459.9
blood2,3 41 434.4 15.4–1410.6 0/0 min.–max
intenstine3 37 208.2 18.5–933.2 2/0 min.–475.9

Spearman's correlation coefficients (R) between the total mercury concentration (ng HgTOT g-1 d.w.) in claws of herring gulls and the total mercury concentration (ng HgTOT g-1 d.w.) in their selected internal organs, tissues and feathers

selected variable n R P equation
outermost primary P10 44 0.38 0.010 claws = 0.2193 x outermost primary P10 + 1078.1857
innermost primary P1 40 n.s
breast contour feathers 46 0.35 0.016 claws = 0.1697 x breast contour feathers + 982.1230
rectrices 45 0.32 0.030 claws = 0.34228 x rectrices + 923.6664
down 17 n.s
breast contour feathers (new) 12 n.s
liver 48 0.39 0.006 claws = 0.4929 x liver + 980.5223
kidney 45 0.50 0.000 claws = 0.771 x kidney + 809.6370
lungs 46 0.45 0.002 claws = 1.5575 x lungs + 677.7302
muscle 49 0.34 0.018 claws = 1.0795 x muscle + 888.1018
heart 48 0.40 0.005 claws = 1.5484 x heart + 763.8899
brain 43 0.47 0.002 claws = 3.5917 x brain + 475.8652
blood 41 0.47 0.002 claws = 1.0740 x blood + 767.8458
intestines 37 0.48 0.003 claws = 2.6663 x intestines + 628.7789

Ackerman, J.T., Eagels-Smith, C.A. Herzog, M.P., Hartman C.A., Peterson, S.H. et al. (2016). Avian mercury exposure and toxicological risk across western North America: A synthesis. Science of the Total Environment 568: 749–769. Ackerman J.T. Eagels-Smith C.A. Herzog, M.P. Hartman C.A. Peterson S.H. 2016 Avian mercury exposure and toxicological risk across western North America: A synthesis Science of the Total Environment 568 749 76910.1016/j.scitotenv.2016.03.071Search in Google Scholar

Bearhop, S., Furness, R.W., Hilton, G.M., Votier, S.C. & Waldron, S. (2003). A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material. Funct. Ecol. 17: 270–275. Bearhop S. Furness R.W. Hilton G.M. Votier S.C. Waldron S. 2003 A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material Funct. Ecol 17 270 27510.1046/j.1365-2435.2003.00725.xSearch in Google Scholar

Becker, P.H. (1992). Egg mercury levels decline with the layingsequence in charadriiformes. Bull. Environ. Contam. Toxicol. 48: 762–767. Becker P.H. 1992 Egg mercury levels decline with the layingsequence in charadriiformes Bull. Environ. Contam. Toxicol 48 762 767Search in Google Scholar

Bełdowska, M. (2016). The direction of changes in the circulation of mercury in the coastal zone of southern Baltic against weather anomalies. In L. Falkowska (Ed.), Rtęć w Srodowisku – Identyfikacja zagrożeń dla zdrowia człowieka (pp. 39–42). Gdansk: Wydawnictwo Uniwersytetu Gdańskiego. (In Polish). Bełdowska M. 2016 The direction of changes in the circulation of mercury in the coastal zone of southern Baltic against weather anomalies Falkowska L. Rtęć w Srodowisku – Identyfikacja zagrożeń dla zdrowia człowieka 39 42 Gdansk Wydawnictwo Uniwersytetu Gdańskiego (In Polish)Search in Google Scholar

Blum, J.D., Popp, B.N., Drazen, J.C., Choy, C.A. & Johnson, M.W. (2013) Methylmercury production below the mixed layer in the North Pacific Ocean. Nat. Geosci. 6: 879–884. 10.1038/ngeo1918 Blum J.D. Popp B.N. Drazen J.C. Choy C.A. Johnson M.W. 2013 Methylmercury production below the mixed layer in the North Pacific Ocean Nat. Geosci 6 879 884 10.1038/ngeo1918Otwórz DOISearch in Google Scholar

Bond, A.L. & Diamond, A.W. (2009). Total and methyl mercury contaminations in seabird feathers and eggs. Arch. Environ. Contam. Toxicol. 56: 286–291. Bond A.L. Diamond A.W. 2009 Total and methyl mercury contaminations in seabird feathers and eggs Arch. Environ. Contam. Toxicol 56 286 29110.1007/s00244-008-9185-7Search in Google Scholar

Braune, B.M. & Gaskin, D.E. (1987). Mercury levels in Bonaparte's gulls (Larus philadelphia) during autumn molt in the Quoddy region, New Brunswick, Canada. Arch. Environ. Contam. Toxicol. 16: 539–549. Braune B.M. Gaskin D.E. 1987 Mercury levels in Bonaparte's gulls (Larus philadelphia) during autumn molt in the Quoddy region, New Brunswick, Canada Arch. Environ. Contam. Toxicol 16 539 54910.1007/BF01055810Search in Google Scholar

Burger, J. & Gochfeld, M. (1997). Risk, Mercury levels, and birds: relating adverse laboratory effects to field biomonitoring. Environmental Research 75: 160–172. Burger J. Gochfeld M. 1997 Risk, Mercury levels, and birds: relating adverse laboratory effects to field biomonitoring Environmental Research 75 160 17210.1006/enrs.1997.3778Search in Google Scholar

Burger, J. & Gochfeld, M. (2002). Effects on chemicals and pollution in seabirds. In E.A. Schreiber & J. Burger (Eds.), Biology of marine birds (pp. 484–525). New York: CRC Press. Burger J. Gochfeld M. 2002 Effects on chemicals and pollution in seabirds Schreiber E.A. Burger J. Biology of marine birds 484 525 New York CRC PressSearch in Google Scholar

Burgess, N.M., Bond, A.L., Herbert, C.E., Neugebauer, E. & Champoux, L. (2013). Mercury trends in herring gull (Larus argentatus) eggs from Atlantic Canada 1972–2008: temporal change or dietary shift? Environ. Pollut. 172: 216–222. Burgess N.M. Bond A.L. Herbert C.E. Neugebauer E. Champoux L. 2013 Mercury trends in herring gull (Larus argentatus) eggs from Atlantic Canada 1972–2008: temporal change or dietary shift? Environ. Pollut 172 216 22210.1016/j.envpol.2012.09.001Search in Google Scholar

Cossa, D. & Martin, J.M. (1991). Mercury in the Rhone delta and adjacent marine areas. Marine Chemistry 36: 291–302. Cossa D. Martin J.M. 1991 Mercury in the Rhone delta and adjacent marine areas Marine Chemistry 36 291 30210.1016/S0304-4203(09)90067-6Search in Google Scholar

Dauwe,T., Bervoets, L., Pinxten, R., Blust, R. & Eens, M. (2003). Variation of heavy metals within and among feathers of birds of prey: effects of molt and external contamination. Environ. Pollut. 124: 429–436. Dauwe T. Bervoets L. Pinxten R. Blust R. Eens M. 2003 Variation of heavy metals within and among feathers of birds of prey: effects of molt and external contamination Environ. Pollut 124 429 43610.1016/S0269-7491(03)00044-7Search in Google Scholar

Ethier, D.M., Kyle, C.J., Kyser,T.K. & Nocera, J.J. (2010). Variability in the growth patterns of the cornified claw sheath among vertebrates: implications for using biogeochemistry to study animal movement. Can. J. Zool. 88: 1043–1051. Ethier D.M. Kyle C.J. Kyser T.K. Nocera J.J. 2010 Variability in the growth patterns of the cornified claw sheath among vertebrates: implications for using biogeochemistry to study animal movement Can. J. Zool 88 1043 105110.1139/Z10-073Search in Google Scholar

Falkowska, L., Grajewska, A., Staniszewska, M., Nehring, I., Szumiło-Pilarska, E. et al. (2017). Inhalation – Route of EDC exposure in seabirds (Larus argentatus) from the Southern Baltic. Marine Pollution Bulletin 117(1 –2): 111–117. Falkowska L. Grajewska A. Staniszewska M. Nehring I. Szumiło-Pilarska E. 2017 Inhalation – Route of EDC exposure in seabirds (Larus argentatus) from the Southern Baltic Marine Pollution Bulletin 1171 –2 111 11710.1016/j.marpolbul.2017.01.060Search in Google Scholar

Falkowska, L., Reindl, A.R., Grajewska, A. & Lewandowska, A.U. (2016). Organochlorine contaminants in the muscle, liver and brain of seabirds (Larus) from the coastal area of the Southern Baltic. Ecotoxicology and Environmental Safety 133: 63–72. 10.1016/j.ecoenv.2016.06.042 Falkowska L. Reindl A.R. Grajewska A. Lewandowska A.U. 2016 Organochlorine contaminants in the muscle, liver and brain of seabirds (Larus) from the coastal area of the Southern Baltic Ecotoxicology and Environmental Safety 133 63 72 10.1016/j.ecoenv.2016.06.042Otwórz DOISearch in Google Scholar

Falkowska, L., Reindl, A.R., Szumiło, E., Kwaśniak, J., Staniszewska, M. et al. (2013). Mercury and chlorinated pesticides on the highest level of the food web as exemplified by herring from the Southern Baltic and African penguins from zoo. Water, Air, and Soil Pollution 224:1549–1563. Falkowska L. Reindl A.R. Szumiło E. Kwaśniak J. Staniszewska M. 2013 Mercury and chlorinated pesticides on the highest level of the food web as exemplified by herring from the Southern Baltic and African penguins from zoo Water, Air, and Soil Pollution 2241549 156310.1007/s11270-013-1549-6Search in Google Scholar

Fitzgerald, W.F., Lamborg, C.H. & Hammerschmidt, C.R. (2007). Marine biogeochemical cycling of mercury. Chem. Rev. 107: 641 –662. 10.1021/cr050353m Fitzgerald W.F. Lamborg C.H. Hammerschmidt C.R. 2007 Marine biogeochemical cycling of mercury Chem. Rev 107 641 662 10.1021/cr050353mOtwórz DOISearch in Google Scholar

Fridolfsson, A.K. & Ellegren, H. (1999). A simple and universal method for molecular sexing of non-ratite birds. Journal of Avian Biology 20: 116–121. Fridolfsson A.K. Ellegren H. 1999 A simple and universal method for molecular sexing of non-ratite birds Journal of Avian Biology 20 116 12110.2307/3677252Search in Google Scholar

Furness, R.W. & Camphuysen, K.C. (1997). Seabirds as monitors of the marine environment. ICES Journal of Marine Science 54: 726–737. Furness R.W. Camphuysen K.C. 1997 Seabirds as monitors of the marine environment ICES Journal of Marine Science 54 726 73710.1006/jmsc.1997.0243Search in Google Scholar

Georgescu, B., Carmen Georgescu, C., Stelian Dărăban, S., Bouaru, A. & Paşcalău, S., (2011). Heavy Metals Acting as Endocrine Disrupters. Scientific Papers: Animal Science and Biotechnologies 44(2): 89–93. Georgescu B. Carmen Georgescu C. Stelian Dărăban S. Bouaru A. Paşcalău S. 2011 Heavy Metals Acting as Endocrine Disrupters Scientific Papers: Animal Science and Biotechnologies 442 89 93Search in Google Scholar

Goede, A.A. &de Bruin, M. (1984). The use of bird feather parts as a monitor for metal pollution. Environmental Pollution Series B, Chemical and Physical 8(4): 281 –298. Goede A.A. &de Bruin, M. 1984 The use of bird feather parts as a monitor for metal pollution Environmental Pollution Series B, Chemical and Physical 84 281 29810.1016/0143-148X(84)90028-4Search in Google Scholar

Grajewska, A., Falkowska, L., Szumiło-Pilarska, E., Hajdrych, J., Szubska, M. et al. (2015). Mercury in the eggs of aquatic birds from the Gulf of Gdansk and Wloclawek Dam (Poland). Environ. Sci. Pollut. Res. 22(13): 9889–9898. Grajewska A. Falkowska L. Szumiło-Pilarska E. Hajdrych J. Szubska M. 2015 Mercury in the eggs of aquatic birds from the Gulf of Gdansk and Wloclawek Dam (Poland) Environ. Sci. Pollut. Res 2213 9889 989810.1007/s11356-015-4154-ySearch in Google Scholar

Hahn, S., Dimitrov, D., Rehse, S., Yohannes, E. & Jenni, L. (2014). Avian claw morphometry and growth determine the temporal pattern of archived stable isotopes. Journal of Avian Biology 45: 202–207. Hahn S. Dimitrov D. Rehse S. Yohannes E. Jenni L. 2014 Avian claw morphometry and growth determine the temporal pattern of archived stable isotopes Journal of Avian Biology 45 202 20710.1111/j.1600-048X.2013.00324.xSearch in Google Scholar

HELCOM (2010) Hazardous substances in the Baltic Sea – an integrated thematic assessment of hazardous substances in the Baltic Sea. Baltic Sea Environ. Proc. No. 120B. Helsinki Commission, Helsinki, Finland, 116 pp. HELCOM 2010 Hazardous substances in the Baltic Sea – an integrated thematic assessment of hazardous substances in the Baltic Sea Baltic Sea Environ. Proc. No. 120B Helsinki Commission Helsinki, Finland 116Search in Google Scholar

Hoefer, H.L. (2012). Grooming in Pets. Compendium: Continuing Education for Veterinarians Retrieved from http://vetfolio-vetstreet.s3.amazonaws.com/94/d714j_ohs-2019-0015_ref_078db11e1806d005056ad4734/file/PV0412_Hoefer-2%203-13.pdf Hoefer H.L. 2012 Grooming in Pets Compendium: Continuing Education for Veterinarians Retrieved from http://vetfolio-vetstreet.s3.amazonaws.com/94/d714j_ohs-2019-0015_ref_078db11e1806d005056ad4734/file/PV0412_Hoefer-2%203-13.pdfSearch in Google Scholar

Kahle, S. & Becker, P.H. (1999). Bird blood as an indicatorfor mercury in the Environment. Chemosphere 39: 2451–2457. Kahle S. Becker P.H. 1999 Bird blood as an indicatorfor mercury in the Environment Chemosphere 39 2451 245710.1016/S0045-6535(99)00154-XSearch in Google Scholar

Kalisinska, E. & Dziubak, K. (2007). Rtęć u gągoła Bucephala clangula z Zalewu Szczecińskiego. Ochr. Środ. Zas. Nat. 31 : 404–409. (In Polish). Kalisinska E. Dziubak K. 2007 Rtęć u gągoła Bucephala clangula z Zalewu Szczecińskiego Ochr. Środ. Zas. Nat 31 404–409 (In Polish)Search in Google Scholar

Kim, E.Y., Murakami, T., Saeki, K. & Tatsukawa, R. (1996). Mercury levels and its chemical form in tissues and organs of seabirds. Arch. Environ. Contam. Toxicol. 30: 259–266. Kim E.Y. Murakami T. Saeki K. Tatsukawa R. 1996 Mercury levels and its chemical form in tissues and organs of seabirds Arch. Environ. Contam. Toxicol 30 259 26610.1007/BF00215806Search in Google Scholar

Kojadinovic, J., Bustamante, P., Churlaud, C., Cosson, R.P. & Le Corre, M. (2007). Mercury in seabird feathers: insight on dietary habits and evidence for exposure levels in the western Indian Ocean. Sci. Total Environ. 384(1–3): 194– 204. Kojadinovic J. Bustamante P. Churlaud C. Cosson R.P. Le Corre M. 2007 Mercury in seabird feathers: insight on dietary habits and evidence for exposure levels in the western Indian Ocean Sci. Total Environ 384 1–3 194– 20410.1016/j.scitotenv.2007.05.018Search in Google Scholar

Kruszewicz, A.G. (2011). Ptaki Polski od A do Ż. Warszawa, Multico Oficyna Wydawnicza. (In Polish). Kruszewicz A.G. 2011 Ptaki Polski od A do Ż Warszawa Multico Oficyna Wydawnicza (In Polish)Search in Google Scholar

Lucas, A.M. & Stettenheim, P.R. (1972). Avian anatomy. Integument. Washington, D.C., U.S. Deptartment of Agriculture. Lucas A.M. Stettenheim P.R. 1972 Avian anatomy. Integument Washington, D.C U.S. Deptartment of AgricultureSearch in Google Scholar

Malling Olsen, K. & Larsson, H. (2004). Gulls of Europe, Asia and North America. Christopher Helm, London 65(83): 128– 141,254–278,438–452. Malling Olsen K. Larsson H. 2004 Gulls of Europe, Asia and North America Christopher Helm London 6583 128– 141254–278438–452Search in Google Scholar

Mallory, M.L., Robinson, S.A., Hebert, C.E. & Forbes, M.R. (2010). Seabirds as indicators of aquatic ecosystem conditions: a case for gathering multiple proxies of seabird health. Marine Pollution Bulletin 60: 7–12. Mallory M.L. Robinson S.A. Hebert C.E. Forbes M.R. 2010 Seabirds as indicators of aquatic ecosystem conditions: a case for gathering multiple proxies of seabird health Marine Pollution Bulletin 60 7 1210.1016/j.marpolbul.2009.08.024Search in Google Scholar

Meissner, W. Staniszewska, J. & Bzoma, S. (2007). Abundance, species composition and age structure of gulls Laridae in the Gulf of Gdansk area during non-breeding season. Ornithological Notes 48: 67–81. Meissner W. Staniszewska, J. Bzoma S. 2007 Abundance, species composition and age structure of gulls Laridae in the Gulf of Gdansk area during non-breeding season Ornithological Notes 48 67 81Search in Google Scholar

Monteiro, L.R. & Furness, R.W. (1995). Seabirds as monitors of mercury in the marine Environment. Water, Air, and Soil Pollution 80: 851–870. Monteiro L.R. Furness R.W. 1995 Seabirds as monitors of mercury in the marine Environment Water, Air, and Soil Pollution 80 851 87010.1007/978-94-011-0153-0_90Search in Google Scholar

Poulin, J. & Gibb, H. (2008) Mercury: Assessing the environmental burden of disease at national and local levels. In A. Prüss-Üstün (Ed.) World Health Organization, Geneva, 2008. (WHO Environmental Burden of Disease Series No. 16). Poulin J. Gibb H. 2008 Mercury: Assessing the environmental burden of disease at national and local levels Prüss-Üstün A. World Health Organization Geneva 2008 (WHO Environmental Burden of Disease Series No. 16)Search in Google Scholar

Reindl, A.R., Falkowska, L. & Grajewska, A. (2015). Chlorinated herbicides in fish, birds and mammals in the Baltic Sea. Water, Air, and Soil Pollution 226: 276. Reindl A.R. Falkowska L. Grajewska A. 2015 Chlorinated herbicides in fish, birds and mammals in the Baltic Sea Water, Air, and Soil Pollution 226 27610.1007/s11270-015-2536-xSearch in Google Scholar

Rozporządzenie Ministra Środowiska z dnia 16 grudnia 2016 r. w sprawie ochrony gatunkowej zwierząt (Journal of Laws of 2016, Item 2183) (In Polish). Rozporządzenie Ministra Środowiska z dnia 16 grudnia 2016 r. w sprawie ochrony gatunkowej zwierząt (Journal of Laws of 2016, Item 2183) (In Polish)Search in Google Scholar

Saniewska, D., Bełdowska, M., Bełdowski, J., Saniewski, M. & Kwaśniak, J. (2010). Distribution of mercury in different environmetal compartments in the aquatic ecosystem of the coastal zone of the Southern Baltic Sea. Journal of Environmental Science 22(8): 1144–1150. Saniewska D. Bełdowska M. Bełdowski J. Saniewski M. Kwaśniak J. 2010 Distribution of mercury in different environmetal compartments in the aquatic ecosystem of the coastal zone of the Southern Baltic Sea Journal of Environmental Science 228 1144 115010.1016/S1001-0742(09)60230-8Search in Google Scholar

Savinov, V.D., Gabrielsen, M.G. & Savinova, T.W.N. (2003). Cadmium, zinc, copper, arsenic, selenium and mercury in seabirds from the Barents Sea: levels, inter-specific and geographical differences. Sci. Total Environ. 306: 133–158. Savinov V.D. Gabrielsen M.G. Savinova T.W.N. 2003 Cadmium, zinc, copper, arsenic, selenium and mercury in seabirds from the Barents Sea: levels, inter-specific and geographical differences Sci. Total Environ 306 133 15810.1016/S0048-9697(02)00489-8Search in Google Scholar

Scheuhammer, A.M, Meyer, M.W., Sandheinrich, M.B. & Murray, M.W.(2007). Effects of environmental methylmercury on the health of wild birds, mammals, and fish. AMBIO 36: 12–19. 10.1579/0044-7447(2007)36[12:EOEMOT]2.0.CO;2 Scheuhammer A.M, Meyer, M.W. Sandheinrich M.B. Murray M.W.2007 Effects of environmental methylmercury on the health of wild birds, mammals, and fish AMBIO 36 12 19 10.1579/0044-7447(2007)36[12:EOEMOT]2.0.CO;2Otwórz DOISearch in Google Scholar

Stettenheim, P.R. (2000). The Integumentary Morphology of Modern Birds – An Overview. Integrative and Comparative Biology 40(1): 461–477. Stettenheim P.R. 2000 The Integumentary Morphology of Modern Birds – An Overview Integrative and Comparative Biology 401 461 47710.1093/icb/40.4.461Search in Google Scholar

Stewart, F.M., Phiilips, R.A., Catry, P. & Furness, R.W. (1997). Influence of species, age, and diet on mercury concentration in Shetland seabirds. Marine Ecology Progress Series 151: 237–244. Stewart F.M. Phiilips R.A. Catry P. Furness R.W. 1997 Influence of species, age, and diet on mercury concentration in Shetland seabirds Marine Ecology Progress Series 151 237 24410.3354/meps151237Search in Google Scholar

Szumitło, E., Szubska, M., Meissner, W., Bełdowska, M. & Falkowska, L. (2013). Mercury in immature and adults Herring Gulls (Larus argentatus) wintering on the Gulf of Gdansk area. Oceanological and Hydrobiological Studies 42(3): 260–267. 10.2478/s13545-013-0082-y Szumitło E. Szubska M. Meissner W. Bełdowska M. Falkowska L. 2013 Mercury in immature and adults Herring Gulls (Larus argentatus) wintering on the Gulf of Gdansk area Oceanological and Hydrobiological Studies 423 260 267 10.2478/s13545-013-0082-yOtwórz DOISearch in Google Scholar

Szumiło-Pilarska, E., Grajewska, A., Falkowska, L., Hajdrych, J., Meissner, W. et al. (2016). Species differences in total mercury concentration in gulls from the Gulf of Gdansk (Southern Baltic). J. Trace Elem. Med. Biol. 33: 100-109. 10.1016/j.jtemb.2015.09.005 Szumiło-Pilarska E. Grajewska A. Falkowska L. Hajdrych J. Meissner W. 2016 Species differences in total mercury concentration in gulls from the Gulf of Gdansk (Southern Baltic) J. Trace Elem. Med. Biol 33 100 109 10.1016/j.jtemb.2015.09.005Otwórz DOISearch in Google Scholar

Szumiło-Pilarska, E., Falkowska, L., Grajewska, A. & Meissner, W. (2017). Mercury in feathers and blood of gulls from the Southern Baltic coast, Poland. Water, Air, and Soil Pollution 228: 138. 10.1007/s11270-017-3308-6 Szumiło-Pilarska E. Falkowska L. Grajewska A. Meissner W. 2017 Mercury in feathers and blood of gulls from the Southern Baltic coast, Poland Water, Air, and Soil Pollution 228 138 10.1007/s11270-017-3308-6Otwórz DOISearch in Google Scholar

Thompson, D.R., Hamer, K.C. & Furness, R.W. (1991). Mercury accumulation in great skuas Catharacta skua of known age and sex, and its effects upon breeding and survival. Journal of Applied Ecology 28: 672–684. Thompson D.R. Hamer K.C. Furness R.W. 1991 Mercury accumulation in great skuas Catharacta skua of known age and sex, and its effects upon breeding and survival Journal of Applied Ecology 28 672 68410.2307/2404575Search in Google Scholar

Thompson, D.R., Becker, P.H. & Furness, R.W. (1993). Long-term changes in mercury concentrations in herring gulls Larus argentatus and common terns Sterna hirundo from the German North Sea Coast. Journal of Applied Ecology 30: 316–320. Thompson D.R. Becker P.H. Furness R.W. 1993 Long-term changes in mercury concentrations in herring gulls Larus argentatus and common terns Sterna hirundo from the German North Sea Coast Journal of Applied Ecology 30 316 32010.2307/2404633Search in Google Scholar

Thompson, D.R., Bearhop, S., Speakman, J.R. & Furness, R.W. (1998). Feathers as a means of monitoring mercury in seabirds: insights from stable isotope analysis. Environmental Pollution 101: 193–200. Thompson D.R. Bearhop S. Speakman J.R. Furness R.W. 1998 Feathers as a means of monitoring mercury in seabirds: insights from stable isotope analysis Environmental Pollution 101 193 20010.1016/S0269-7491(98)00078-5Search in Google Scholar

WHO/IPCS. (1990). Environmental Health Criteria (EHC) 101: Methylmercury. Geneva: World Health Organization, International Programme on Chemical Safety. WHO/IPCS 1990 Environmental Health Criteria (EHC) 101: Methylmercury Geneva World Health Organization, International Programme on Chemical SafetySearch in Google Scholar

Yin, X., Xia, L., Sun, L., Luo, H. & Wang, Y. (2008). Animal excrement: a potential biomonitor of heavy metal contamination in the marine environment. Sci. Total Environ. 399: 179–185. Yin X. Xia L. Sun L. Luo H. Wang Y. 2008 Animal excrement: a potential biomonitor of heavy metal contamination in the marine environment Sci. Total Environ 399 179 18510.1016/j.scitotenv.2008.03.00518466955Search in Google Scholar

Zamani-Ahmadmahmoodi, R., Alahverdi, M. & Mirzaei, R. (2014). Mercury concentrations in common tern Sterna hirundo and slender-billed gull Larus genei from the Shadegan Marshes of Iran, in north-western corner of the Persian Gulf. Biological Trace Element Research 159: 161– 166. Zamani-Ahmadmahmoodi R. Alahverdi M. Mirzaei R. 2014 Mercury concentrations in common tern Sterna hirundo and slender-billed gull Larus genei from the Shadegan Marshes of Iran, in north-western corner of the Persian Gulf Biological Trace Element Research 159 161– 16610.1007/s12011-014-0006-824819088Search in Google Scholar

Polecane artykuły z Trend MD

Zaplanuj zdalną konferencję ze Sciendo