Fróðskaparrit - 01.01.2007, Page 164

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SOFT BOTTOM MACRO FAUNA SPECIES COMPOSITION IN FAROESE FJORDS
the others. After a scrutiny of the individu-
als from these samples it is obvious that
two species are the major contributors to
the high N/S ratio, Myriochele sp. and
Phoronis sp. These two species are some-
times found in very large numbers and
have a patchy distribution on the seabed
(Oug, 2000). The most abundant species
were Myriochele sp„ Phoronis sp, Abra ni-
tida, Thyasira spp., Ennucula (Nuculoma)
tenuis, Heteromastes filiformis (probably
misidentified with Mediomastes firagilis),
Chaetozone setosa and Diplocirrus glau-
cus. Compared to the present paper Myri-
ochele sp„ Phoronis sp. and Ennucula
(Nuculoma) tenuis are not among the five
most frequent species. The Shannon in-
dices for each separate sample were be-
tween 1.67 and 3.81 with an average of
2.51 which is clearly lower than the aver-
age of 3.5 in this paper. The Pielou even-
ness index is also quite low (0.62) com-
pared to 0.74 in this paper.
A general comparison between the re-
sults from Nørrevang (1990) and the pres-
ent paper shows lower diversity indices
and a higher dominance by a few species.
Also the composition of species is a little
different. A likely explanation for this dif-
ference could be that the sample stations in
Nørrevang (1990) were placed in the deep-
est parts of the fjords where the organic
content of the sediments are high and the
oxygen conditions at least in late summer
are unfavorable.
Jørgensen (1993) sampled five locali-
ties in Skálafjørður and analyzed for
macrofauna and physical/chemical param-
eters. From the data she concluded that the
benthic fauna could be separated into three
different community types. One shallow
water community type on the sill at the
fjord entrance, another community type in
the deepest part of the ijord and a third
community type at the innermost part of
the ljord. A total of about 107 different
species from 12 different phyla were iden-
tified from all stations. Eleven different
species were among the five most common
species from each station (Table 7). Com-
pared with the present paper there are a
few species with a common high fre-
quency, they are Heteromastes filiformis
(probably identical with Mediomastus fra-
gilis), Thyasira flexuosa/gouldii and Abra
nitida. The average species number per 0.1
m2 was 34 (22-49) and this is a little higher
compared to the present paper (Table 1)
which was 29 (5-66). The average abun-
dance per 0.1 m2 was 814 (361-2293)
which is about three times higher com-
pared to the present paper (Table 1). The
average ratio between number of individu-
als and the number of species per sample
was 23.8 (9.5-46.8) which also is about
three times the value found in this paper
(Table 1). If we look at the distribution oí
the species number in major taxonomic
groups we get the usual picture with a
heavy domination of polychaetes, fol-
lowed by a distinctly lower number ol
molluscs. This is comparable with our fin-
dings.
Sakarisson (2000) investigated two sta-
tions from Skálafjord sampled in 1998 and
one station from Kaldbakstjørður sampleđ
in 1999. All samples were sampled with
0.1 m2 grab and stations SK05 and SK09