Seaweed Responses to Temperature - Seaweed Biology - page 49

Vigh et al. 1998 ). High temperatures cause an increase in the fluidity of membranes,
which ultimately leads to a disintegration of the lipid bilayer.
The impairment of photosynthesis at low temperature appears to be primarily
related to impaired synthesis and functioning of photosynthetic pigment-protein
complexes (Robertson et al. 1993 ; Nie et al. 1995 ) and reduced activities of key
enzymes in the Calvin cycle (Holaday et al. 1992 ; Huner et al. 1993 ; Kingston-
Smith et al. 1997 ). There are also several target sites for the impairment of
photosynthesis at high temperatures, such as the CO 2 fixation system, photophos-
phorylation, the electron transport chain, and the oxygen evolving complex
(Sharkey 2005 ; Allakhverdiev et al. 2008 ). Especially various parameters of fast
chlorophyll fluorescence transients of photosystem II, such as the maximum and
effective quantum yield (Fv/Fm,

PSII), the minimum fluorescence (Fo), and
photochemical and non-photochemical quenching of chlorophyll fluorescence,
have been widely used to monitor temperature-induced changes of photosynthetic
activity in seaweeds (e.g., Antarctic Palmaria decipiens , Arctic Fucus distichus :
Becker et al. 2009 , warm-temperate Valonia utricularis : Eggert et al. 2003b ,
tropical to warm-temperate Laurencia spp.: Padilla-Gamiˇo and Carpenter 2007 ).

F

3.3 Phenotypic Temperature Acclimation of Growth
and Photosynthesis

Most seaweeds have the ability to acclimate growth and photosynthesis in response
to changes in ambient temperature, both to daily temperature changes and on a
seasonal timescale. Beneficial phenotypic acclimation ( sensu Leroi et al. 1994 )is
the improvement of a thermal trait (e.g., growth, photosynthesis) at the respective
ambient temperature that allows to maximize performance over a broad tempera-
ture range. The potential for temperature acclimation varies between species and is
expected to be higher in eurythermal than in stenothermal species. Accordingly,
seaweeds native to habitats with large annual temperature variations typically
display a stronger ability to acclimate than species from habitats with more stable
seasonal regimes. Seasonal acclimation of photosynthesis has been described for
seaweeds from the temperate regions (Davison 1987 ;K ubler and Davison 1995 ;

Pfetzing et al. 2000 ; Eggert et al. 2006 ; Padilla-Gamiˇo and Carpenter 2007 ).
Likewise, acclimation has been described in a number of intertidal species (Smith
and Berry 1986 ; Kim et al. 2009 ; Henkel et al. 2009 ). In contrast, a limited
acclimation potential has been described for Antarctic and tropical species (Eggert
and Wiencke 2000 ; Eggert et al. 2006 ).
The fact that temperature changes can induce cellular acclimation responses
indicates that temperature is sensed and that the temperature signal is immediately
transduced into the cell. Membrane fluidity, protein conformation, cytoskeleton
depolymerization, and metabolic reactions have all been identified to be tempera-
ture sensors (Horvath et al. 1998 ; Los and Murata 2004 ). Enzyme adjustments
to temperature occur constantly as temperature changes on different timescales,

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