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and season responders
sensu
Kain (
1989
). The season anticipators begin growing
under short-day conditions in late winter/spring, often under the sea-ice. Some
species even reproduce in winter. Maximal growth rates occur in spring. Growth
and reproduction in these species are presumably based on circannual rhythms and
photoperiodism, synchronized or triggered by daylength, as shown for some Ant-
arctic (Wiencke
1990a
; Wiencke et al.
1996
) and for many cold-temperate species
(Luning
1988
,
1991
;Luning and Kadel
1993
; Schaffelke and Luning
1994
). The
season responders, in contrast, start growth and reproduction later, not before
favorable light conditions are present in spring and summer. Species of this group
react directly to the primary factors in their environment and show an opportunistic
life strategy (Wiencke
1990a
).
Typical Antarctic season anticipators are the brown algae
Desmarestia
menziesii, D. anceps
,
D. antarctica
,
Himantothallus grandifolius
,
Ascoseira
mirabilis
(Wiencke
1990a
; Drew and Hastings
1992
;G´mez et al.
1995
,
1996
;
G´mez and Wiencke
1997
) and the red algae
Palmaria decipiens
,
Delesseria
salicifolia
,
Gymnogongrus antarcticus
,
G. turquetii
,
Hymenocladiopsis crustigena
,
Trematocarpus antarcticus
, and
Phyllophora ahnfeltioides
(Wiencke
1990b
;
Weykam et al.
1997
; Dummermuth and Wiencke
2003
). Typical Antarctic season
responders are
Adenocystis utricularis
(Wiencke
1990a
), the red algae
Iridaea
cordata
(Weykam et al
1997
) and
Gigartina skottsbergii
(Wiencke
1990b
), and
the green algae
Ulva hookeriana
and
Acrosiphonia arcta
(Wiencke
1990b
).
In contrast to the Southern Ocean in the Arctic there is not only a strong seasonal
variation of the light regime, but also of the levels of the macronutrients nitrate and
phosphate, which are high in winter and low in summer (see Chap.
4
by Gordillo).
Arctic season anticipators like
Laminaria solidungula
and
Saccharina latissima
(
L. saccharina
) take full advantage of these conditions (Chapman and Lindley
1980
;
Dunton
1985
). New blades start to form in
L. solidungula
in fall under decreasing
daylengths. Optimum growth rates occur in late winter/spring under thick ice. In
comparison,
S. latissima
grows mostly during a brief period in late spring, when the
first light penetrates into the water during sea-ice breakup.
As most endemic Antarctic and Arctic seaweeds are season anticipators, this
type of life strategy is therefore regarded as the typical adaptation to the seasonally
changing conditions in polar seas. In contrast, season responders are mostly
distributed also in the adjacent temperate regions. Another difference between
both groups is their depth distribution. Polar season anticipators occur almost
exclusively in the sublittoral, whereas many polar season responders can grow
also in the eulittoral.
As for biomass formation, photosynthetic performance shows also a strong
seasonal pattern (Wiencke et al.
2011
). In large brown algal season anticipators,
photosynthetic rates are highest in late winter/spring (Drew and Hastings
1992
;
G´mez et al.
1995
). As shown in several kelp and kelp-like species, respiration rates
increase indicating growth activity in the basal meristem powered by remobiliza-
tion of carbohydrates from the distal thallus part. An extreme example is
Laminaria
solidungula
, in which the mobilization occurs during the 9 months period of
darkness under the ice, when the alga completes over 90% of its annual growth.
