The Botany of Iceland - 01.12.1912, Síða 179

MARINE ALGAL VEGETATION
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3. Gigartina, widely distributed.
Rhodymenia.
Plumaria elegans.
Delesseria alata.
Acrosiphonia.
Monostroma Grevillei.
Chætomorpha Melagonium.
Delesseria sanguinea and others.
4. Corallina widely distributed, in
a single pool Halosaccion.
5. Laminaria + Alaria.
In another part:
Ascophyllum in quantities between
1 and 2.
It would carry us too far to give several more examples from
the diaries, but on regarding the material taken as a whole it is
distinctly seen that there is no other difference of importance be-
tween the two districts with regard to the zonal division of the
algal vegetation beyond the facl that some of tlie communities and
associations occur in one place and are absent from the other. The
division of the belts varies somewhat in both places which is
chieíly due to the greater or smaller degree of exposure of the
locality (see Part VI).
The most conspicuous difference in the division of the belts
in E. Iceland and S. Iceland is due to the enormous size of the
Corallina-heh in the latter place. This community (Gigartina, Coral-
lina and others; see Part VI) occurs just below the Fucus-be\t where,
for instance, in the Vestmannaeyjar it is the dominant one; this
also applies to Eyrarbakki and the south side of Reykjanes, but
perhaps to a somewdiat less degree. This leaves less room for the
Rhodymenia-community (Rhodgmenia, Halosaccion; see Part VI), which
also forms a belt below the Fucus-belt; consequently it is not so
large there as in E. Iceland where it is extremely common and in
several places widely extended. In many places in SW. Iceland
the Rhodymenia-commumty is as large as in E. Iceland.
The sea off the coast of S. Iceland is in movement everywhere,
and calm water is almost unknown. The calm-water-vegetation
proper, which is so common within the Qords of E. Iceland, is
therefore absent from S. Iceland, but is again found richly repre-
sented in SW., NW. and N. Iceland.
The luxuriancy of the vegetation is somewhat similar in
both places; it appears, however, to be greater in the Vestmanna-
eyjar and the western part of the south coast.
Depth-limit. It appears that there is reason to believe (see
Part V) that the algal vegetation extends to greater depths in the
fjords of E. Iceland than on the south coast, but as this cannot be
regarded as sufíiciently proved I shall not enter into it more fully.