Fróðskaparrit - 01.01.1998, Síða 267

MAKROSTEINRENNINGARRANNSÓKNIR AV VATNSÁLØGUM
ÚR SKÁLAFIRÐI í FØROYUM: FYRIBILS ÚRSLIT
273
are new to the fossil fauna of the Faroes.
Tha lacustrine sediments did not contain
carbonates, but the inner chitinous linings
of freshwater ostracodes were present in
most samples. Daphnia was represented by
ephippia, whereas the other cladocerans
were represented by shells and head
shields. Eurycercus remains were not pre-
sent in the lower part of the sequence, and
it is possible that this genus immigrated
somewhat later to the Faroe Islands than the
other taxa of Cladocera found during this
study. Three statoblasts belonging to two
taxa of freshwater bryozoa (Plumatella sp.
and Cristatella mucedo) were found. These
are present in low numbers, which makes it
difficult to know when these taxa colonized
the lake.
All taxa probably represent species that
still live in the Faroe Islands, and thus a cli-
mate similar to that at the present is in-
ferred. To our knowledge there are no
records of freshwater bryozoa from the
Faroes, but Plumatella repens is widely
distributed in Europe and has been reported
from the Shetland Islands and Iceland, and
it also lives on Greenland (Lacourt, 1968;
Røen, 1977; Steingrímsson, 1985). Finds
of statoblasts of Cristatella mucedo from
Iceland and Greenland indicate that this
species also lives on these islands, and it
has been reported from the Shetland Islands
(Lacourt, 1968; Lredskild, 1983; Stein-
grímsson, 1985). Cristatella mucedo is the
most warmth demanding species identified;
its northem geographical range limit coin-
cides more or less with the arctic tree line.
A sample from 87 cm below the core top
contained a few specimens of the foramini-
fer Egerelloides scabrus. The shell of this
species consists of small sand grains that
are agglutinated togehter. The species can
tolerate somewhat lowered salinities
(Lutze, 1965), as would be expected just af-
ter the first inflow of marine waters into the
former freshwater basin.
The origin of the flora and fauna of the
Laroe Islands has been much debated, and
it has been speculated if some species could
have survived the last glacial stage in ice
free refugia, or whether all species have im-
migrated after the last deglaciation. The
sedimentary record on the islands holds a
great potential to study the history of the
flora and fauna. Whereas the history of the
vascular flora has been studied in some de-
tail (Jóhansen, 1985), few concrete data are
available about the history of the fauna. The
history of a number of taxa can now be ex-
tended back to the early Holocene.
Some insects have been reported from
pre-landnám layers (Buckland, 1988), but
it appears that the insect remains reported
here are the first that are firmly dated to the
early Holocene. It has been suggested that a
major part of the fauna was ice rafted to the
North Atlantic islands from northwest Eu-
rope at the transition from the last glacial
stage to the Holocene (Coope, 1979; 1986;
Buckland etal., 1986). Although rafting by
ice bergs or sea ice may account for the
transport of some species, palaeoceano-
graphic studies indicate that the directions
of the surface currents in the eastern North
Atlantic were not much different from
those at the present during the late-glacial
or Holocene (Koc et al. 1993; Hald and As-
peli, 1997).