The Botany of Iceland - 01.12.1912, Page 55

MARINE ALGAL VEGETATION
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a. The Sea. South of Iceland the salinity varies but slig'htly,
with the exception of the coastal water itself. During the suinmer,
at any rate, the salinity of tlie coastal water must be considerably
lower on account of the great amount of fresh water brought down
by all the rivers of the south. On the other coasts and especially
those of N. and E. Iceland the salinity varies according to whether
the layers of water originate from currents which are deficient in
salt or from the Irminger current, and also with the amount of
fresh water streaming out from land. At station 106 (see above) the
inferior salinity is evidently due to cold water from the Greenland
current, and at station 73 it is probably due to fresh water.
b. The Fjords. The salinity inside the íjords varies consider-
ably and the variation is dependent upon the amount of fresh water
which intermingles with the water in the fjord, partly in the form
of river water and partly in the form of precipitated moisture. The
lowest salinity in the fjords wTas 1.31 %o in Eskifjörður after rain.
Heavy rainfalls must be capable of causing such an inferior salinity
in other places also, especially in narrow' fjords, but this will not
last long, and as the littoral algæ can endure heavy showers during
low-tide, they wdll not suffer to any extent wmrth mentioning.
In places where the salinity is as lowT as in Seyðisfjörður
(9.23 %o), wThere a rather large river disembogues, the algal vegeta-
tion occurs sparingly, although algæ are found, especially green and
browTn algæ. At a place like Borgarnes, where the salinity is low
(18.9; 26.9) on account of fresh water from Hvítá, the algal vegeta-
tion occurs more abundantly than at the very head of Seyðisfjörður
by the river, but the inferior salinity excludes certain species, for
instance, Polysiphonia fastigíata, although Ascophyllum occurs abun-
dantly. Further out, where the sea is more saline, it is not absent.
It is especially in the surface-water of the fjords that tlie sali-
nity varies so much. It is greater in the large open fjords, such as
Faxaflói, than in the small land-Iocked fjords, such as Hvalfjörður,
a circumstance which niust cerlainly be due to river-water. The
tigures given show also that the salinity of the surface-water of the
smaller fjords is less in the inner part than in the outer part. The
same difíerence seems to appear also between the deeper layers of
water of the inner and outer parts.
As a rule, the salinity of the deeper layers is higher and more
stable, which must be beneficial to the vegetation in the depths.