Seaweeds and Their Communities in Polar Regions - Seaweed Biology - page 261

A general characteristic of the floras of both polar regions is their low species
richness. In the Antarctic, about 130 species have been documented (Wulff et al.
2011 ) and in the Arctic about 150 species have been recorded (Wilce 1994 ). These
numbers will likely increase with increased exploration of these remote areas of our
planet. In Antarctica, species richness is highest in the Antarctic Peninsula region
and lowest in the southernmost part of the Ross Sea at 77 S (Wiencke and Clayton
2002 ). In the Arctic, species richness peaks with about 70 species around Svalbard,
followed by the Canadian High Arctic (mainly Baffin Bay area) with 55 species.
The Russian Arctic principally harbors an impoverished Svalbard flora. Similarly,
species richness decreases in eastern Greenland from the south to the north.
Whereas the seaweed flora in southernmost Greenland is relatively rich (Pedersen
1976 ), in the Alaskan Beaufort Sea shelf west of the Canadian Arctic Archipelago
only 15 species were recorded (Dunton and Schonberg 2000 ; Wulff et al. 2011 ).
Two other characteristics of the Antarctic seaweed flora must be mentioned here:
First, a conspicuous feature of the Antarctic seaweed flora, compared to temperate
regions, is the scarcity of small macroalgal epiphytes. Such epiphytes are, however,
not absent. Rather, they occur as endophytes in larger seaweeds (Peters 2003 ; see
also Chap. 11 by Potin and Chap. 9 by Amsler). Second, the order Desmarestiales,
which ecologically replaces the Laminariales (kelps) in Antarctica, is considered to
have its evolutionary center in the Southern Ocean and subsequently radiated into
the Northern hemisphere (Peters et al. 1997 ).
In contrast to the earlier assumption that Arctic seaweeds are mostly of Atlantic
origin (Wilce 1990 ; Dunton 1992 ), recent molecular data obtained on six red algal
species and of Laminaria solidungula from the Arctic indicate that Arctic and
Atlantic subarctic species are evolutionary based in the North Pacific (Adey et al.
2008 ). Another example of an Arctic invader from the Pacific may be the green alga
Acrosiphonia arcta (van Oppen et al. 1994 ). The species is—as is also Desmarestia
viridis/confervoides —a good example for the evolution and spread of bipolar
distributed species. According to molecular studies, the biogeographic disjunctions
of both species date back to the maximum of the Wurm/Wisconsin glaciation
18,000 years ago (van Oppen et al. 1993 ). The dispersal phases were presumably
microscopic stages which, due to a high temperature tolerance, were able to cross
the tropics (Peters and Breeman 1993 ; Bischoff and Wiencke 1995 ; see also Chap. 18
by Bartsch et al.).
13.3 Physiological Adaptations to the Environment
13.3.1 Seasonal Development and Physiological Performance
In polar regions, adaptation to the strong seasonality of the light regime is one of the
most important prerequisites for the ecological success of seaweeds (Wiencke et al.
2011 ). There are two different growth strategies classified as season anticipators