The Botany of Iceland - 01.12.1912, Síða 57

MARINE ALGAL VEGETATION
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early in May, algæ which had been frozen hard during the night,
apparently quite unharmed and alive when thawed, nor could one
perceive next day that they had suffered at all; but, as I was tra-
velling, I was not able to observe them more than these two days.
It is also a foregone conclusion that the algæ left dry must freeze
in the winter when the cold is severe, but it does not appear that
they suffer thereby.
If the cold cannot be said to have any directly injurious effect,
yet indirectly it may hurt the vegetation (though not to any great
extent) by the fact that the water freezes and the beach becomes
ice-covered. During severe winters a covering of ice may be found
during tlie greater part of the winter in tlie smaller fjords, and
especially where the fjord-water is abundantly mixed with fresh
water, and even if the winters are quite mild, yet from time to
time the water next the beach may freeze. In the littoral zone and
on rocks which are laid bare during low-tide, the ice forms in ac-
cordance with the substratum, and if this is uneven the ice breaks.
At high-water the ice-covering is lifted up; the pieces of ice may
then freeze together again, and break once more with the next ebb-
tide. During spring-tides in particular these movements are rather
considerable and the plant-covering may be a good deal damaged
thereby: but if one regards the coasts in their entirety these distur-
bances will prove to be of small importance.
The drift-ice is much more dangerous to the algal vegetation
as the icebergs scrape the rocks with which they come in contact.
Strömfelt, when travelling in Iceland in 1883, the year following
one of the years notable on account of the great quantity of ice,
found the littoral vegetation poorly developed in the north country.
This most certainly resulted from the drift-ice having blockaded the
coast during the whole suinmer of 1882. In the summer of 1898, I
saw on the promontory between Seyðistjörður and Loðmundarfjörður
distinct signs of the drift-ice which had been there in the spring.
The injurious influence of the drift-ice consists mainly in the fact
that it scrapes away the vegetation from the parts with which it
comes in contact; possibly also in the fact that it reduces the tem-
perature to far below normal. That the plants suddenly find them-
selves in a much colder medium than they are accustomed to must
produce a check upon them, particularly on the more sensitive
species. The marine plants, however, are less affected by this than
the land vegetation. As a rule, ice-years occur at fairly long intervals;