Biology Reference
In-Depth Information
a
50
40
30
20
10
0
-10
0
12
24
36
48
60
72
84
96
-20
-30
-40
Time (h)
b
3
2
1
0
0
12
24
36
48
60
72
84
96
-1
-2
Time (h)
Fig. 4.1
Diel patterns of nitrate (
a
) and phosphate (
b
) uptake by
Fucus serratus. Black rectangles
represent the dark period [photoperiod 14:10 (L:D)]. Taken from Gordillo et al. (
2002
)
4.3 Uncoupling Uptake and Incorporation
Uptake and incorporation might be temporally and spatially uncoupled. In this
context even storage in the vacuoles could be considered as spatial reallocation;
however, it is more pragmatic to use the term “spatial uncoupling” when resources
are reallocated in different parts of the thallus. In turn, storage in vacuoles is
considered as a temporal uncoupling since nutrients can be immediately made
available for assimilation and incorporation processes occurring in the cell when-
ever they are needed. According to Fujita (
1985
), differences in nutrient storage
capacity between species may be important in structuring algal assemblages in
environments with episodic N supply.
One of the most remarkable examples of temporal uncoupling is that found in
polar kelps and kelp-like species (see also Chap.
13
by Wiencke and Amsler). The
two polar coastal regions share some major characteristics, including low tempera-
ture and light regimes with complete darkness for months in winter and continuous
sunlight for months in summer, as well as seasonal melting events of large ice
masses. There are also key factors, however, differentiating both systems. In the
Arctic, nutrients drop below detection limits during spring, and remain low until
autumn mainly due to phytoplanktonic blooms occurring right after ice breakup
(Aguilera et al.
2002
). The Antarctic, however, is considered virtually unlimited by
