Fróðskaparrit - 01.07.2004, Side 76

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MERCURY IN LIVER, EGGS AND FEATHER OF BLACK GUILLEMOT
CEPPHUS GRYLLE FAEROENSISIN THE FAROE ISLANDS
metabolites of these, often as a bulk re-
ferred to as persistent organic pollutants,
POPs.
The species investigated have been re-
cruited at several trophic levels, from alga
(Laminaria hyperborea) to invertebrates
like limpets (Patella vulgata) through fish
such as dab (Limanda limand), but most of
all seabirds like black guillemots (Cepphus
grylle) and fulmars (Fulmarus glacialis)
have been subject to study (Dam, 1998a;
2000, Larsen and Dam, 2003; Dam et al.,
2001; Hoydal et al. 2003; Olsen et al.,
2003.).
The task of finding suitable species for
use in regular environmental monitoring
that will reflect the present status of pollu-
tants in a given compartment, often called
indicator species, was initiated by the Food
and Environmental Agency in 1995. The
bird species focussed on in that study was
the black guillemot, Cepphus gryllefaroen-
sis (Asbirk, 1979), which occurs in a dis-
tinct family in the Faroe Islands, and is
thought to be stationary there. The assump-
tion of the black guillemots being station-
ary in the Faroe Islands is quite important
as this property of an indicator species al-
lows the assumption that the pollutant sig-
nature found is reflecting the local pollu-
tion status, being it long-range transported
pollutants or pollutants released locally.
The long-range transported pollutants are
among others PCB and DDT and mercury
(see also http://www.unece.org/env/lrtap/
lrtap_hl.htm ). This does not exclude the
possibility of pollutants being transported
by sea or by animals, but transport by air
masses has been found to be an important
route of transfer of POPs and mercury from
industrialised parts of the hemisphere to
more remote parts. The question of routes
and transport mechanisms of pollutants has
been treated in detail in the multi-lateral
scientific effort Arctic Monitoring and As-
sessment Programme, see for instance
AMAP 1998 and Nilsson and Huntington
(2002).
Apart from the stationarity, the black
guillemot is well suited as an indicator
species because it in several places is found
to have a relatively stable diet consisting of
sandeel, it is thus not mainly an opportunis-
tic scavenge feeder like some other sea-
birds. Another element that makes the
black guillemot better suited as an indicator
species than the other alciids is that in con-
trast to these, it lays two eggs, thus allow-
ing for sampling of one egg from the clutch
without emptying the nest. The reason for
sampling eggs is that these make good ma-
trices for monitoring of a variety of pollu-
tants.
Monitoring of metals in bird feathers is
much preferred to for instance monitoring
liver tissue due to the nonintrusive nature of
the sampling method. The application of
feathers in monitoring the occurrence of
bioavailable mercury has been the subject
in several studies, among which the studies
describing the sturdiness of feathers as a
monitoring matrix and their representativi-
ty of blood mercury levels are of particular
interest (Appelquist et al., 1984; Goede et
al., 1989; Lewis and Furness, 1991; Mon-
teiro and Furness 1995; Bearhop et al.
2000). In essence it has been found that
mercury is excreted into feathers during