Fróðskaparrit - 01.07.2004, Side 116

114
MERCURY IN THE FAROE ISLANDS — A REVIEW OF AVAILABLE DATA
1,2
oi 0,8
■§> 0,6
E. 0,4
I 0,2
31,1 32,4 33,1 29,8 31 30,4 32,1 31,5 31,9
AM AM AF AM AF AM AM AF AF
4 12 6 8 5 8 18 8 14
Sveipur Sveipur Sveipur Hestoy Hestoy Hestoy t l:S=7:11 H:S=1:7 I co ii W 4*
nov-95 apr-96 apr-96 aug-96 aug-96 nov-96 jan-97 jan-97 jan-97
Fig. 11 Mercury in Black guillemot s are givenfor groups ofadult males (AM), adultfemale (AF) and juvenile males
(JM) in mg/kg ww liver. Under the bars, the dry weight, %, is shown, along with group description incl. number of
samples in the pools and sampling areaand period.(Adapted from Dam, 1998b).
comparison between feather mercury con-
centrations in the Black guillemot plumage
should await a species-specific description
on interfeather variation preferentially in
the population in question.
Liver and muscle tissue
The first study integrating biological para-
meters and environmental pollutants con-
centrations in various trophic levels in the
coastal zone in the Faroe Islands were done
on material sampled in the period 1995-
1997 and the study included black guille-
mot as a representative of a stationary
seabird species (Dam, 2000). In this study,
the diet of black guillemots were analysed
through stomach contents and the result
was not as expected, where the major dif-
ference to the expectations was that black
guillemots obviously had a much greater
variety in its food choice than anticipated.
Also, it was found that there were marked
summer and winter diets, with fish domi-
nating in the early summer and crustacea in
winter (Dam, 2000). At the same time, a
similar investigation was undertaken on ei-
der (Somateria mollissima) and to a small-
er extent on shag (Phalacrocorax arit-
sotelis) (Dam, 1998b; 1998c). Overall, a
large number of birds was analysed for
heavy metals and persistent organic pollu-
tants, both to elucidate seasonal trends and
differences among sexes and age groups.
The majority of the analyses were done on
pools of birds of similar age/sex, and thus
individual variability can not be described,
the results still give a fair amount of data,
and may as such serve as valuable reference
for future studies.
The results of the food choice studies
(Dam, 1998b) showed that the eider feeds
on a variety of gastropods and bivalves
whereas the shag is a dedicated fish eater.
Mercury concentrations (Table 13) are