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■ SUMMARY
Tephra-eating lugworms in
SUBMERGEÐ PEAT IN SOUTHEAST
ICELAND
The lugworm Arenicola marina (Linné) is
widely distributed in Iceland where it is a char-
acteristic species for niuddy sands in tidal flats
and down to about 6 m water dcpth. It seems to
be equally common in the low-arctic regions of
the north and east coasts and the high-boreal
areas along the west and south coasts. The
lugworm generally lives in a J-shaped burrow
with a small depression above the oral end. The
animal usually ingests muddy sand with detri-
tus and microorganisms, and deposits the char-
acteristic faecal heaps above the anal cnd.
In the Hornatjörður region in Southeast Ice-
land, lugworms were observed that had bur-
rowed in subnterged peat containing lephra lay-
ers. Some of thc worms were ingesting the
lighl-gray tephra from the Öræfajökull eruption
of 1362 and the resulting light-coloured faecal
heaps were very prominent on the surface of the
dark tidal llats. The tephra-eating lugworms
seem to thrive well and, apparenlly, the sharp-
edged glass shards do not damage the digestive
organs of the animals. The peat submerged af-
ter the tephra fell in 1362, due to later glacio-
isostatic subsidence during the climatic deterio-
ration of the „Little Ice Age“ (1600-1900). Af-
ter 1900 there has been glacio-isostatic rise of
land in the area, due to climatic amelioration
and melting of glaciers, resulling in rising of
the submerged peat to the water level, llius
gradually restricting the lugwornt habitats. As
sediments have been washed away from the top
of the rising peat, lugworms have started to bur-
row into the peat, thus adapting to the environ-
mental changes.
PÓSTFANG HÖFUNDA/AUTHORS' ADDRESS
Leifur A. Símonarson
Raunvísindastofnun Háskólans/
Science Institute
Jarðfræðahúsi Háskólans
IS-101 REYKJAVÍK
Páll Imsland
Raunvísindastofnun Háskólans/
Science Inslitute
Dunhaga 3
IS-107 REYKJAVÍK
163