Environmental Engineering Reference
In-Depth Information
(Yoshioka
1997
). Finally, carbon assimilation by various kinds of phytoplankton,
such as
S. costatum
,
Microcystis
spp. and others (Fogel et al.
1992
; Francois et al.
1993
; Yoshioka
1997
; Takahashi et al.
1990
; Herczeg and Fairbanks
1987
; Hinga
et al.
1994
) may operate under almost constant CO
2
demand, amounting on average
to 4.4
μ
M in seawater and 0.29
μ
M in freshwater (Yoshioka
1997
). Phytoplankton
photosynthesis is largely dependent on habitats (either seawater or freshwater), and
on phytoplankton species that have variable efficiency for CCM. The process involves
either active transport of HCO
3
−
−
by a cell-surface
carbonic anhydrase and CO
2
transport (MacIntyre et al.
2000
; Badger and Price
1992
;
Tortell et al.
1997
; Berman-Frank et al.
1998
; Nimer et al.
1999
).
, or coupled dehydration of HCO
3
5.3 Variation in Temperature
Temperature, driven by solar radiation, is one of the key factors for variating
the primary production by photosynthesis in natural waters (Sobek et al.
2007
;
Mortain-Bertrand et al.
1988
; Davison
1991
; Wilen et al.
1995
; Lesser and
Gorbunov
2001
; Baulch et al.
2005
; Doyle et al.
2005
; Yoshiyama and Sharp
2006
; Ogweno et al.
2008
; Bouman et al.
2010
; Fu et al.
2007
). This effect can be
discussed, based on aquatic microorganisms and higher plants.
Temperature Effects on Aquatic Microorganisms
Cyanobacteria, the most ancient life forms on earth, are unusual prokaryotic micro-
organisms that are able to perform oxygenic photosynthesis. Optimum growth, with
respect to optimal temperatures, is in this case influenced by their ability to toler-
ate temperature stress, such extreme cold in Antarctica (where temperatures never
exceed
−
20 °C) and in water pockets of Antarctic lake ice, where temperatures are
always below 0 °C. At the opposite end of the variation scale there are extremely
high temperatures such as 55-60 °C and even the case of hot springs, where temper-
atures reach 70 °C (Schopf et al.
1965
; Meeks and Castenholz
1971
; Margulis
1975
;
Priscu et al.
1998
; Psenner and Sattler
1998
; Ward et al.
1998
).
At ambient water temperature (WT), the primary excitation requires 2-3 ps,
and the subsequent electron transfer to the primary quinone QA exhibits multipha-
sic kinetics (80-300 ps) (Dashdorj et al.
2004
). It is commonly considered that
that the primary excitation occurs within 1-3 ps after the creation of the electroni-
cally excited special pair P700* (Brettel
1997
; Dashdorj et al.
2004
). The state of
thylakoid membranes in cyanobacteria plays a prominent role in the tolerance of
the photosynthetic machinery to environmental stresses, such as cold (chilling)
(Wada et al.
1990
; Murata et al.
1992
).
At low temperatures, ultrafast time-resolved spectroscopy suggests multiexpo-
nential evolution of the excited state and of photoproduct populations, even when
excitation takes place in the red edge of the absorption spectrum (Germano et al.
2004
). The different time components observed at low temperatures are generally
recognized to produce charge separation. The latter can either take place through
