Biology Reference
In-Depth Information
13.2 Biodiversity and Biogeographical Relationships
of Antarctic and Arctic Seaweeds
As mentioned above, both polar regions differ considerably with respect to their
genesis and cold-water history. Antarctica is an ice-covered continent surrounded
by the Southern Ocean without any land connection to temperate regions since the
Mesozoic (Lawver et al.
1985
). The Antarctic Circumpolar Current (ACC), which
started to develop at about 32 Ma and became persistent around 15 Ma, amplifies
this separation further (Hommersand et al.
2011
). Driven by westerly winds, it
flows clockwise around the continent. In contrast, the Arctic Ocean is a “mediter-
ranean” sea surrounded by continental land masses and is continuously connected
to the temperate coasts of Eurasia and America. The Arctic Polar Front is discon-
tinuous and there is a strong influx of warm North Atlantic water into the Arctic
through the Fram Strait between Spitsbergen and Greenland (Zacher et al.
2011
). In
contrast, the Antarctic region is sharply delimited to the north by the forceful
Antarctic Polar Front. A second feature differentiating the two polar regions is
their cold-water history. Whereas Antarctica became glaciated 14 million years ago
(Crame
1993
), a perennial ice cover over the Arctic Ocean did not develop before
0.7-2.0 Ma (Clarke
1990
). So, seawater temperatures have been low for a much
longer time in the Antarctic compared to the Arctic (Zacher et al.
2011
).
These differences have resulted in strongly different biodiversity patterns in both
polar regions. In the Antarctic region, 35% of the species are endemic, whereas only
few endemic Arctic species have been identified so far (Wiencke and Clayton
2002
;
Wulff et al.
2011
). In the Antarctic, 44% of the Heterokontophyta (Phaeophyceae and
Chrysophyceae), 36% of the Rhodophyta, and 18% of the Chlorophyta are endemic
and the number of endemic species is continuously increasing. Only recently,
Hommersand et al. (
2011
) described four new genera and five new endemic red
algal species. There is also one endemic order, the brown algal order Ascoseirales.
Conspicuous and ecologically important endemic species include the brown algae
Himantothallus grandifolius
,
Desmarestia anceps
,
D. menziesii
,
Cystosphaera
jacquinotii
,
Ascoseira mirabilis
, and the red algae
Myriogramme manginii
,
Georgiella
confluens
,
Phycodrys antarctica
,
Trematocarpus antarcticus
, and others. The red
algae
Palmaria decipiens
and
Iridaea cordata
occur from the Ross Sea in the south
to a few sub-Antarctic islands in the north (Wiencke and Clayton
2002
).
In contrast to the high degree of endemism in Antarctica, only very few seaweed
species endemic to the Arctic have been detected (Wilce
1990
; Wilce et al.
2009
).
These include the brown algae
Chukchia pedicellata
,
C. endophytica
,
Punctaria
glacialis
,
Platysiphon verticillatus
, the red alga
Petrocelis polygyna
, and the green
alga
Acrosiphonia incurva
. Most species from the Arctic have a distribution that
extends well into the temperate region, e.g., the red algae
Devaleraea ramentacea
,
Turnerella pennyi
,
Dilsea integra
, and
Pantoneura baerii
. This is also the case for
the kelp
Laminaria solidungula
, but this species is regarded as a true Arctic species
as its occurrence in the temperate region is restricted to cold, deep waters (Muller
et al.
2011
).
