COLONIZATION OF THE LAND
Invertebrate Fauna on Surtsey
The Early Colonists
The first insect was discovered on Surtsey
in May 1964. The discovery of other invertebrates of various species
followed. As was expected, these were mostly flying insects to begin
with, and they arrived on Surtsey via their own wings and favourable
winds. On the one hand, there were species that were carried with northerly
winds from Vestmannaeyjar (Westman Islands) or the Icelandic mainland.
On the other hand, there were accidental species that were borne to
Surtsey with winds from the European continent. Spiders were also discovered
soon after the birth of Surtsey, gliding easily through the air attached
to spinning threads.
insect species floated on the sea surface to Surtsey, either with or
without the aid of drifting material. Animals – both dead and
alive – have been found on the beach after being washed ashore.
There are examples of transportation on floating grass turfs with soil
and driftwood that have stranded upon the beach, carrying numerous small
animals. In addition, birds have carried small animals to the island.
During the first years in Surtsey’s
history, both the arrival of small animals and their efforts to colonize
the island were under close inspection. Supervision of the project was
in the hands of Carl H. Lindroth, professor of Entomology at Lund University
in Sweden. He carried out this research until 1972. Högni Böðvarsson,
professor in Stockholm, was on Lindroth’s research team and continued
the study of soil organisms until 1978. Erling Ólafsson carried
out research on other groups until 1981, when research was discontinued
temporarily. In 1995, Peter Gjelstrup from Aarhus, Denmark, and Hólmfríður
Sigurðardóttir conducted studies of soil animals (mites and
Collembola). In 2002, monitoring of the invertebrate colonization of
Surtsey was resumed by Erling Ólafsson and his team.
Development of the Invertebrate
During the first few years, a total of
170 different insect species were found on the island. This represents
approximately 13% of all species found in Iceland until that time. Unfortunately
only a few of these species had become established, which is not surprising,
as conditions on the island were very harsh and not favourable for colonization
for quite a while. When Surtsey was visited in 1981, it became obvious
that several species had become permanently established, and these formed
an interesting community. In this community there were animals that
were herbivores, others that were saprotrophs, and still others that
were carnivores. By this time, gulls (great black-backed gull and herring
gull) had begun breeding, with a few scattered nests over the island.
This developing gull colony with increasing vegetation was the basis
for the invertebrate community. Following the establishment of a distinct
gull colony in 1985, the vegetation and soil fertility underwent a revolutionary
change. Consequently, the invertebrate fauna was affected.
In the summer of 1993, the first earthworms
were found on Surtsey in soil samples taken from the gull colony. The
worms in question were juvenile chestnut worms (Lumbricus castaneus).
Earthworms have not been found there since.
When soil animals were studied in 1995,
the vegetation had become very lush in the gull colony and the soil
fauna very diverse. Before that time, 16 different species of Collembola
had been found, but in 1995 eight species were found, six of which were
new to the island. It came as a surprise that only a few of the first
species had become established. On the other hand, the diversity of
mites had grown, with a total of 62 species in 1995.
In a study carried out in 2002, it became
clear that a landmark had been reached in the succession of the invertebrate
fauna. Animals were collected in pitfall traps within permanent vegetation
plots that had been established on the island. In addition, small flying
insects were caught in sweeping nets and collected. In this study a
total of 76 invertebrate species were found, half of them for the first
time on the island. Soil animals were plentiful, but they have not been
identified yet and are not included in this figure.
total of 300 different species of invertebrates have been found on Surtsey,
and approximately half of them have become permanently established.
Flying insects are the most conspicuous in the fauna, but among the
wingless species there are a few of interest. One is Ceutorrhyncus
insularis, a very small snout beetle that feeds on scurvy grass
and is an extremely rare species on a global scale. Two land snail species
have been found: the Western Glass-snail (Vitrina pellucida),
; and the slug Deroceras agreste. In addition, 10 species of
Linyphiidae have been found in Surtsey, six of them in 2002.
Invertebrates found on Surtsey till 2002:
||e.g., ants, bees, wasps
Erling Ólafsson - email@example.com)
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