Biology Reference
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grow in a very narrow temperature range between 0 and 5 C (Bischoff-B
asmann
and Wiencke 1996 ; Eggert and Wiencke 2000 ). Other Antarctic species with a
distribution extending to Tierra del Fuego and subantarctic islands have more
eurythermal temperature characteristics. For example, Gymnogongrus antarcticus
and Phyllophora ahnfeltioides grow between 0 and 10 C (Bischoff-Basmann and
Wiencke 1996 ; Eggert and Wiencke 2000 ). Compared to the Antarctic, seaweeds
from the Arctic have a shorter cold water history of about 3 Ma (Briggs 1995 ) which
explains the less cold-adapted and more eurythermal characteristics of Arctic
species. For example, sporophytes of the kelp Laminaria solidungula grow between
0 and 15 C with an optimum at 5-10 C (tom Dieck 1992 ). Temperate species
exhibit the widest performance breadth as they experience largest seasonal temper-
ature changes. Cold-temperate Northeast Pacific and North Atlantic species grow
between 0 and 18(20) C with optima between 5 and 15 C (e.g., Bolton and L
uning
1982 ;L
uning and Freshwater 1988 ; tom Dieck 1992 ; Wiencke et al. 1994 ), while
warm-temperate Atlantic species grow at up to 23-24 C and have slightly elevated
optima (e.g., tom Dieck and Oliveira 1993 ). Additionally, life history stages (i.e.,
macrothalli/microthalli) of temperate seaweeds with a heteromorphic life history
often have different temperature-response curves leading to an overall eurythermal
temperature adaptation of the species (tom Dieck 1993 ). Tropical seaweeds from
the Indo-West Pacific have the highest temperature optima of growth at 25-30 C
(Pakker and Breeman 1996 ; Bischoff-B
asmann et al. 1997 ).
Similar to growth, photosynthetic temperature responses also reflect adapta-
tion to the local temperature regimes. Seaweeds from colder environments reach
higher photosynthetic rates at low temperatures, while seaweeds native to
warmer environments exhibit superior photosynthetic rates at higher temperatures.
Optimum temperatures for photosynthesis are lowest (10-20 C) in Antarctic
macroalgae (Wiencke et al. 1993 ; Eggert and Wiencke 2000 ), intermediate
(20-25 C) in cold-temperate to Arctic species, and highest (25-35 C) in warm-
temperate to tropical species (Terrados and Ros 1992 ). Thus, temperature optima of
photosynthesis are situated well above the temperature optima of growth (Davison
1987 ;Kubler et al. 1991 ; Eggert and Wiencke 2000 ; see also Chap. 13 by Wiencke
and Amsler). This shows that temperature effects on a specific physiological
process (i.e., photosynthesis in this case) do not necessarily correspond to the
temperature-growth pattern as growth integrates the effect of temperature on the
total metabolism.
As a consequence of the long cold water history of the Antarctic Ocean, very
specific adaptations have evolved in endemic Antarctic species. Eastman ( 1993 )
detected “DNA decay” in Antarctic fish, i.e., loss of genetic information not
required for life at ambient temperatures (Hoffmann and Willi 2008 ). Ice-binding
proteins have been found in Antarctic sea ice diatoms as a very specific adaptation
to the very low, freezing temperatures in this extreme habitat. The extracellular
proteins are associated with the diatom community and they serve to prevent
freezing injury (Janech et al. 2006 ). However, it has not been investigated whether
these or other types of low-temperature adaptation have evolved in polar seaweeds
as well.
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