The Botany of Iceland - 01.12.1912, Blaðsíða 111

MARINE ALGAL VEGETATION
97
low-water mark of neap-tide, and is exposed during each lowr-
tide; the upper littoral zone is, then, the littoral zone proper,
which doubtless corresponds exactly with Kolderup Rosenvinge’s
limitation of the littoral zone in Greenland, but not entirely with
Börgesen’s limitation of tlie littoral zone in the Færöes, as some
of the Færöese littoral associations seetn to belong lo the next belt.
The semi-littoral zone extends from about the low-water
mark of neap-tide to a depth of about 10 metres, and thus extends
over the lower littoral zone, and even lower than that. In reality
this zone comprises the lower littoral zone including stragglers belowr
the low-water mark of spring-tide to a depth of 10 metres. That
part of the zone lying in the lower littoral zone is laid bare at and
about spring-tide, but is submerged at neap-tide.
The sublittoral zone extends from the low-water mark of spring-
tide to the absolute depth-limit.
There seems to me to be no reason for calling any part of the
Benthos elittoral. Even if the 40-metre contour is a lower limit of
growth in the case of several species, and is, approximately, the
lower boundary of the La/nina/'ia-community, jret the upper bound-
ary of the red-algæ communities which extend further downwrards
than 40 metres lies much higher, and the 40-metre contour thus
cuts straight through natural communities. It cannot, therefore, be
considered the principal boundary as regards the wrhole of the
constantljr-submerged vegetation. Strömfelt (1. c.) is of the opinion
that, possibly, elittoral vegetation does not exist on the coasts of
Iceland. According to Kjellman the elittoral vegetation is extremely
poor in species, and probably has a limited distribution everywrhere
in the northern seas. From what has been said above respecting
the 40-metre line, and from a comparison with Greenland (Rosen-
vinge, 63) and the Færöes (Börgesen, 11 and 12), it is obvious
that a division of the constantly-submerged vegetation at this depth-
line is not quite natural in the northern seas. It is more correct,
therefore, to do as Rosenvinge and Börgesen do, and to class
the vegetation as sublittoral down to the absolute depth-limit.
In the following I do not employ tlie term “region,” which is
nowr generally used to describe somewrhat limited subdivisions of
The Botany of Iceland. I. 7