14
K. M. G. Mostofa et al.
3.2.2 Photosynthesis
Photosynthesis is the key process for the formation of organic carbon or OM
(e.g. algae or cyanobacteria, phytoplankton, etc.) through light-stimulated inorganic carbon acquisition in surface waters (Mostofa et al. 2009a; Komissarov
1994, 1995, 2003; Li et al. 2011; Li 1994; Zubkov and Tarran 2008; Beardall
et al. 2009a, b; Wu and Gao 2009; Liu et al. 2010). Photosynthetic organisms are
then able to produce autochthonous DOM via photoinduced respiration (or photoinduced assimilation) and microbial respiration or assimilation in natural waters
(Mostofa et al. 2009b; Zhang et al. 2009; Conrad 1999; Weiss et al. 1991; Harvey
et al. 1995; Fu et al. 2010; Thomas and Lara 1995; Druon et al. 2010; Yamashita
et al. 2008). A new hypothesis on photosynthesis also considers that H 2 O 2 might
be involved in the occurrence of oxygenic photosynthesis in both higher plants
(Komissarov 1994, 1995, 2003; Miller and Moran 1997) and natural water organisms (Mostofa et al. 2009a, b). Occurrence of photosynthesis in natural waters
includes two facts: the first is the generation of numerous chemical species from
DOM, which may proceed as follows: (i) photoinduced degradation of DOM can
produce many photoproducts, such as H 2 O 2 , CO 2 , DIC, CO, LMW DOM, and
so on in upper surface waters (Mostofa and Sakugawa 2009; Miller and Zepp
1995; Miller 1998; Johannessen and Miller 2001; Ma and Green 2004; Xie et al.
2004; Johannessen et al. 2007; Salonen and Vähätalo 1994; Amon and Benner
1996; Granéli et al. 1996; Remington et al. 2011; Zepp et al. 1998; Cai et al. 1999;
Gennings et al. 2001; Clark et al. 2004; Fichot and Miller 2010; White et al. 2010;
Cai 2011); (ii) microbial degradation of DOM including DON and DOP can produce compounds such as H 2 O 2 , CO 2 , DIC, PO 4
3− , NH 4
+ , CH 4 , LMW DOM and
so on (Mostofa and Sakugawa 2009; Zhang et al. 2004; Vähätalo and Järvinen
2007; Lovley et al. 1996; Ma and Green 2004; Palenik and Morel 1988; Li et al.
2011; Zinder 1990; Kotsyurbenko et al. 2001; Zagarese et al. 2001; Semiletov
et al. 2007). Many of these compounds can favor the occurrence of photosynthesis either directly or indirectly and lead to fixation of organic carbon or OM from
inorganic carbon in surface waters (Mostofa et al. 2009a; Komissarov 1994, 1995,
2003; Miller and Moran 1997; Li et al. 2011; Ortega-Retuerta et al. 2009; Li 1994;
Zubkov and Tarran 2008; Beardall et al. 2009a, b; Wu and Gao 2009; Liu et al.
2010).
A general scheme for the photoinduced (Eq. 3.1) and microbial or biological
(Eq. 3.2) degradation of DOM can be expressed as follows (Mostofa et al. 2009a, b):
The second fact is that H 2 O 2 and CO 2 , produced by either photoinduced or
microbial degradation of DOM and POM can take part to photosynthesis, to form
new OM or carbohydrate-type compounds (Mostofa et al. 2009a, b):
(3.1)
DOM + hυ → H 2 O 2 + CO 2 + DIC + CO + LMW DOM
(3.2)
DOM + microbes → CO 2 + DIC + PO 4
3− + NH 4
+ + CH 4 + LMW DOM
K. M. G. Mostofa et al.
3.2.2 Photosynthesis
Photosynthesis is the key process for the formation of organic carbon or OM
(e.g. algae or cyanobacteria, phytoplankton, etc.) through light-stimulated inorganic carbon acquisition in surface waters (Mostofa et al. 2009a; Komissarov
1994, 1995, 2003; Li et al. 2011; Li 1994; Zubkov and Tarran 2008; Beardall
et al. 2009a, b; Wu and Gao 2009; Liu et al. 2010). Photosynthetic organisms are
then able to produce autochthonous DOM via photoinduced respiration (or photoinduced assimilation) and microbial respiration or assimilation in natural waters
(Mostofa et al. 2009b; Zhang et al. 2009; Conrad 1999; Weiss et al. 1991; Harvey
et al. 1995; Fu et al. 2010; Thomas and Lara 1995; Druon et al. 2010; Yamashita
et al. 2008). A new hypothesis on photosynthesis also considers that H 2 O 2 might
be involved in the occurrence of oxygenic photosynthesis in both higher plants
(Komissarov 1994, 1995, 2003; Miller and Moran 1997) and natural water organisms (Mostofa et al. 2009a, b). Occurrence of photosynthesis in natural waters
includes two facts: the first is the generation of numerous chemical species from
DOM, which may proceed as follows: (i) photoinduced degradation of DOM can
produce many photoproducts, such as H 2 O 2 , CO 2 , DIC, CO, LMW DOM, and
so on in upper surface waters (Mostofa and Sakugawa 2009; Miller and Zepp
1995; Miller 1998; Johannessen and Miller 2001; Ma and Green 2004; Xie et al.
2004; Johannessen et al. 2007; Salonen and Vähätalo 1994; Amon and Benner
1996; Granéli et al. 1996; Remington et al. 2011; Zepp et al. 1998; Cai et al. 1999;
Gennings et al. 2001; Clark et al. 2004; Fichot and Miller 2010; White et al. 2010;
Cai 2011); (ii) microbial degradation of DOM including DON and DOP can produce compounds such as H 2 O 2 , CO 2 , DIC, PO 4
3− , NH 4
+ , CH 4 , LMW DOM and
so on (Mostofa and Sakugawa 2009; Zhang et al. 2004; Vähätalo and Järvinen
2007; Lovley et al. 1996; Ma and Green 2004; Palenik and Morel 1988; Li et al.
2011; Zinder 1990; Kotsyurbenko et al. 2001; Zagarese et al. 2001; Semiletov
et al. 2007). Many of these compounds can favor the occurrence of photosynthesis either directly or indirectly and lead to fixation of organic carbon or OM from
inorganic carbon in surface waters (Mostofa et al. 2009a; Komissarov 1994, 1995,
2003; Miller and Moran 1997; Li et al. 2011; Ortega-Retuerta et al. 2009; Li 1994;
Zubkov and Tarran 2008; Beardall et al. 2009a, b; Wu and Gao 2009; Liu et al.
2010).
A general scheme for the photoinduced (Eq. 3.1) and microbial or biological
(Eq. 3.2) degradation of DOM can be expressed as follows (Mostofa et al. 2009a, b):
The second fact is that H 2 O 2 and CO 2 , produced by either photoinduced or
microbial degradation of DOM and POM can take part to photosynthesis, to form
new OM or carbohydrate-type compounds (Mostofa et al. 2009a, b):
(3.1)
DOM + hυ → H 2 O 2 + CO 2 + DIC + CO + LMW DOM
(3.2)
DOM + microbes → CO 2 + DIC + PO 4
3− + NH 4
+ + CH 4 + LMW DOM