Fróðskaparrit - 01.01.2009, Page 181

EVNAFRØÐILIGAR BLEYTBOTNSDÁTUR Á FØROYSKUM HAVØKI:
LÍVRUNNIÐ TILFAR, NITROGEN, FOSFOR, SINK OG KOPAR
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year to year, but, aside from SK05, these lo-
calities have relative constant values, only
disturbed by a single year. If the single de-
viant values are excluded from the data,
SK07 had values between 9.7 and 12.2 %
(2000 excluded), Cøtuvík 3.2-5.8 % (2003 ex-
cluded), Árnafjørður 3.5-3.8 (2003 excluded),
Miðvágur 2.3-2.7 % (2005 excluded) and
Undir síðu 4.3-6.1 % (2006 excluded). Pri-
mary production on the Faroe Plateau
changes from year to year and some of the
variability in LOI values could be explained
by this fact. Also, since each fjord may be re-
garded as a separate ecosystem, there may
be a variation in primary production be-
tween fjords (Gaard et al., 1992). Another
reason that may underlie the deviant values
in LOI is patchiness of the organic content in
the sediments within the same locality.
The presented data are from sediment
samples collected throughout the year, al-
though the majority of samples were col-
lected from June to December. Some of the
variability could be explained by differences
in organic content in the sediment at differ-
ent times of the year.
The fact that organic content in sedi-
ments vary and for some years show deviant
values demands that a certain number of
replicate samples from each locality be taken
to maintain reliability, e.g„ three replicates.
If inshore data from the Faroe area are
compared to offshore data, it seems like the
offshore sediments have a lower content of
organic materials. Values were between 0.5 -
13.8 % in inshore waters, compared to 1.3 -
5.6 % in offshore sediments.
Besides the data from the present paper,
there are only two reports with information
on nitrogen and phosphorus in marine sed-
Figure 11. Sampling sites reported by Mannvik and
Petersen (2002).
iments from the Faroe Islands (Hoydal and
Dam, 2004; Johansen, 2006). All samples are
from shallow waters (< 100 m) and the ni-
trogen values were all between 0.14 and 4.9
g/kg dry sediment, while the phosphorus
values were in the range 0.43 - 2.02 g/kg dry
sediment. Nitrogen does not show any rela-
tion to depth.
From the data in this paper, it would ap-
pear that the copper and zinc concentra-
tions in the inshore sediments are higher in
shallow water areas, compared to the deeper
areas. Copper had values from 14 to 120
mg/kg dry sediment in shallow waters, com-
pared to 5-38 mg/kg dry sediment in deeper
waters. The zinc values were in the range 12-
98 mg/kg dry sediment in shallow waters