Mercury in Different Feather Types from Great Cormorants (Phalacrocorax carbo L.) Inhabiting the Vistula Lagoon Ecosystem in Poland
Magorzata Misztal-Szkudlin ska
Mercury Feathers Cormorant CV-AAS
P. Konieczka J. Namiesnik Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology
, ul. Narutowicza 11/12, 80-952 Gdansk,
M. Misztal-Szkudlinska P. Szefer (&) Department of Food Sciences, Medical University of Gdansk
. Gen. J. Hallera 107, 80-416 Gdansk,
Total mercury levels in different feather types (down, contour, tail and flight) in Great Cormorants (Phalacrocorax carbo L.) were determined using CV-AAS. Feathers from Great Cormorants inhabiting the Vistula Lagoon ecosystem have an average Hg level of 7.14 3.99 (lg/g w.w.). Age-dependent concentrations of Hg were statistically significant (ANOVA Kruskal-Wallis, p 0.0001). There were also significant differences in Hg levels in different parts of feathers from adults and immature birds (ANOVA KruskalWallis, p \ 0.0001). Cormorant chick feathers appear to be a potential biomonitor of Hg pollution in the Vistula Lagoon ecosystem, but this subject requires further research.
In aquatic environments Hg is converted to methylmercury
and in this form is rapidly incorporated into the food chain.
Aquatic birds, which are top predators in the food chain,
may be exposed to significant concentrations of Hg. Its
toxic effects in birds include reduced food intake, leading
to weight loss; progressive weakness in the wings and legs,
making flight, walking and standing difficult; an inability to
coordinate muscle movements. High Hg levels in birds
most often affect their immune, detoxification and nervous
systems; they also impair reproduction (Boening 2000). On
the basis of a limited number of data, Burger and Gochfeld
(2000) claimed that feather Hg levels from 5 to 40 lg/
g d.w. led to lower reproduction and survival. Feathers of
fish-eating birds could serve as good monitors of spatial
and temporal patterns of Hg contamination in water
ecosystems (Ochoa-acun a et al. 2002).
Metal pollutants can be incorporated into birds feathers
along three routes: from the blood during feather growth,
from the excretion of salt or the secretion of preen glands,
and through contact with the habitat (Goede and de Bruin
1984). Feathers may serve as a useful indicator of inorganic
pollutants because concentrations of metals correlate well
with their internal levels during the time of feather
formation. Moreover, mercury levels in feathers are stable,
and the metal may bind to the sulphydryl groups of the
keratin as the feathers grow. The most important pathway
of mercury elimination in birds is its excretion when the
feathers are moulted (Ochoa-acuna et al. 2002; Dauwe
et al. 2003). The aim of the present study was to analyse
total mercury levels in feathers from Great Cormorants
inhabiting the Vistula Lagoon and to compare them with
concentrations reported from the feathers of other aquatic
Materials and Methods
Different parts of feathers were taken from 62 Great
Cormorants. These birds are present in Poland during the
breeding season from February or March to September. In
this country they enjoy partial species protection status
(Dz.U. z 2004 r. Nr 220, poz. 2237). The breeding colony
(a nature reserve) from which feather samples were taken is
situated at Katy Rybackie (54 210N, 19 140E) near the
Vistula Lagoon; this is the largest breeding colony of the
Great Cormorant in Europe.
The cormorants were captured in 2006 by permission of
the local environment protection authorities and were aged
on the basis of plumage characteristics. The feathers of
adult cormorants are black with white spots on the cheeks
and thighs. Immature birds have a white belly with a
variable number of dark spots. There is no sexual dimorphism.
The moult strategy in cormorant is difficult to interpret
because birds replace feathers singly during the course of
the season (Nelson 2005).
The birds were segregated as follows: 7 chicks, 11
immatures (5 females, 6 males) and 44 mature birds (20
females, 24 males). Down, contour, flight and tail feathers
were taken from adult and immature specimens, but only
the tail feathers from the chicks. The tail feathers from 18
adult and immature birds were cut up into the feather tip,
inner vane, outer vane, shaft and calamus (Fig. 1).
The feather samples were rinsed three timeswith
water ? detergent, then with distilled water ? acetone
(1:1) and finally with Milli-Q waterafter which they were
dried overnight at room temperature to constant mass (Saeki
et al. 2000). The samples were homogenized and then
decomposed at 800 C in a flow of clean air. Hg was
determined by CV-AAS at 253.65 nm (MA-2000 Mercury
Analyzer). Three analytical subsamples were prepared from
each sample. A pooled sample consisted of 35 feathers.
Quality was assured by analyses of certified reference
materials, i.e. CRMs: DORM-2 (National Research Council,
Canada) and BCR-463 (IRMM, Belgium). Recoveries of
total Hg were 101.0% and 97.1% respectively and the SDs
were 0.09% and 0.09% respectively. The limit of detection
for the method was 0.096 ng and the limit of quantification
was 0.29 ng. Other validation parameters for the analytical
method were reported by Konieczka et al. (2010).
The statistical analyses were performed using the
STATISTICA 9.0 for Windows (Copyright StatSoft, Inc.
19842010) and Graph Pad Prism 5.0. The data were
processed using the ANOVA KruskalWallis test to check for
any significant (p \ 0.0001) difference between Hg
concentration and age. Where a statistically significant variation
was found, the post hoc Dunn test was applied to seek a more
detailed relation. Dunns post hoc test compares the
difference in the sum of ranks between two columns with the
expected average difference (Motulsky 2005).
Results and Discussion
The average total Hg concentration in cormorant feathers
was 7.14 3.99 lg/g d.w. (0.631.20 lg/g d.w.). The
average Hg level in chick feathers was 1.16 0.5 lg/
g d.w. (Table 1).
Fig. 1 Feather parts
Figure 2 shows that there are statistically significant
age-dependent variations in Hg concentrations in feathers
(ANOVA KruskalWallis, H = 18.14, p \ 0.0001). The
post hoc Dunn test was used to check for a more specific
relation. The concentration differences were significant in
chicks and adults (test post hoc Dunn, p \ 0.001), as well
as in chicks and immature birds (test post hoc Dunn,
p \ 0.01).
Figure 3 shows that there are also statistically significant
variations in the Hg content of the different feather types
from adults and immature birds (ANOVA KruskalWallis,
H = 30.37, p \ 0.0001). The Dunn post hoc test revealed a
statistically significant differentiation of concentration
between contour tail feathers, contour and flights (p \ 0.05),
down tail feathers as well as down flights (p \ 0.001).
There were no significant differences in Hg levels
between the sexes.
Table 1 Mercury levels in
Great Cormorant feather types
Great Cormorant (Phalacrocorax carbo) Hg SD and range (lg/g w.w.)
Adult (N = 44)
Immature (N = 11)
Fig. 2 Concentrations of the total Hg (lg/g d.w.) in all the feathers
of chicks, immatures and adults of Great Cormorants inhabiting the
Vistula Lagoon ecosystem
Fig. 3 Concentrations of the total Hg (lg/g d.w.) in different types of
Great Cormorant feathers from the Vistula Lagoon ecosystem
Feathers of Great Cormorants from the Vistula Lagoon
ecosystem contain significantly higher levels of Hg than
their counterparts from urban areas in Tokyo, Lake Biwa
and the Mie colony in Japan. According to Saeki et al.
(2000) and Nam et al. (2005), Great Cormorant feathers
contained ca. 3 lg Hg/g d.w. The mercury content in the
Great Cormorant feathers in the present study was similar
to that in feathers of P. carbo from the Caspian Sea in Iran
(Rajaei et al. 2011): 7.92 3.56 and 8 1 lg/g d.w.
respectively. Mazloomi et al. (2008) reported a mean level
of 4.44 lg/g in cormorant feathers from the
Fereidoonkenar region (Iran) in the southern Caspian Sea.
Phalacrocorax auritus from two reservoirs in New Mexico had 4.01
and 2.34 lg Hg/g w.w. in the tail feathers (Caldwell et al.
1999). Very low levels of Hg (0.251 lg/g d.w.) were
reported by Burger and Gochfeld (2001) in the feathers of
Cape Cormorants (Phalacrocorax capensis) from Namibia
(southern Africa). The feathers of the Great Cormorants
that we analysed contained a concentration of Hg similar to
that in Royal Albatrosses (6.8 lg/g d.w.) from the southern
Indian Ocean and Laysan Albatrosses (7.2 lg/g d.w.) from
the North Pacific, as well as Herring Gulls (6.06 lg/g d.w.)
and Glaucous Gulls (5.96 lg/g d.w.) from Chaun in Siberia
(Kim et al. 1996a, b). Boening (2000) and Ochoa-acun a
et al. (2002) found some differences in feather Hg
concentrations across taxonomic bird groups. They assumed
that Hg contents in feathers depended on feeding strategies
and to a lesser extent on differences in the metabolism and
excretion of this metal. Mercury concentrations in birds
also depend on body size, moult strategy, migration
patterns and physiology (Stewart et al. 1997). Fish-eating
birds like cormorants are at risk of higher contents of Hg
because its circulation is associated mainly with water
The results of this study show that Hg levels in feathers
were lower in chicks than in adults. A similar dependence
was reported by Stewart et al. (1997) in Kittwakes, Arctic
Skuas and Common Skuas.
Examination of feather parts revealed only slight
differences in Hg concentrations (lg/g d.w.) outer vane
7.38 6.08, inner vane 7.83 6.62, tip 7.32 6.17,
shaft 7.49 5.7 and calamus 6.83 5.7. This stands in
agreement with the data given by Dauwe et al. (2003) and
implies that mercury is evenly bound during feather
Birds feathers are used as indicators of environmental
pollution because the Hg content in the feathers reflects its
content in the blood at the time of feather formation.
Moreover, Hg levels in feathers are stable, feathers are easy
to collect and their collection is non-invasive (Goede and
de Bruin 1984; Burger and Gochfeld 2000; Boening 2000).
Levels of mercury in growing feathers are directly and
linearly related to its dietary intake by chicks of the same
species of birds (Weech et al. 2006). It appears that
cormorant chick feathers could be used as monitoring material
for measuring the exposure of birds to Hg in the Vistula
Lagoon ecosystem because the chicks are the most highly
exposed to regional metal pollution. This suggestion
requires further research, however.
Acknowledgments The authors gratefully acknowledge the
financial support received from grant No. N305 049336 of the Polish
Ministry of Science and Higher Education. The material for the
research was collected by permission of the local environment
protection authorities. We are indebted to Dr Gerard Kanarek, who
assisted with collecting the biological material.
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