Biology Reference
In-Depth Information
Fig. 3.1
Typical normalized growth temperature-response curves of the stenothermal polar
species
Gymnogongrus skottsbergii
(Antarctica,
circles
, Eggert and Wiencke
2000
), the euryther-
mal temperate species
Laminaria digitata
(Helgoland,
diamonds
, tom Dieck
1992
), and the
tropical species
Wurdemannia miniata
(St. Croix, Caribbean,
squares
, Pakker and Breeman
1996
). The temperature-response curves were estimated by fitting the experimental data to the
function developed by Blanchard et al. (
1996
). The temperature optima of the three response
curves are 0, 12, and 25
C and the 80%-“performance breadths” are
1-1
C, 7-16
C, and
22-28
C for the Antarctic, temperate, and tropical species, respectively
and then rapidly decline near the upper critical temperature. These temperature-
response curves can be characterized quantitatively by estimating various de-
scriptive statistics (e.g., the minimum, maximum, optimum temperature, the
performance breadth). Eggert et al. (
2003a
) introduced the temperature ranges at
which 80% and 20% of the maximal growth rate occurs as arbitrary values for
“good” and for “sufficient” growth, respectively. This approach intrinsically
bypasses the interpretation of the optimum temperature, which is usually a mean-
ingless parameter in the discussion of local temperature adaptation. The “perfor-
mance breadth” (or alternatively the 80% or 20% temperature ranges) can be
interpreted for the concept of eurythermy and stenothermy. Eurythermal seaweeds
have a broad “performance breadth” and typically grow in environments with large
fluctuations in seawater temperature. In contrast, stenothermal species have a
narrow performance breadth and are found in regions with small temperature
fluctuations.
Both the “performance breadth” and the position of the growth temperature-
response curves of seaweeds typically correlate with the local temperature regime,
i.e., reflect local temperature adaptation (Fig.
3.1
). The endemic Antarctic species
have the longest cold water history of at least 14 Ma (Briggs
1995
; Crame
1993
; see
also Chap.
13
by Wiencke and Amsler) which in turn determines their worldwide
lowest temperature requirements (Wiencke et al.
1994
; see also Chap.
18
by
Bartsch et al.). The red macroalgae
Gigartina skottsbergii
and
Ballia callitricha