Environmental Engineering Reference
In-Depth Information
a buildup of apoptosis-inducing ROS in the competing dinoflagellate
Peridinium
gatunense
(Vardi et al.
2002
). A distinct H
2
O
2
maximum at depth in the Southern
Ocean can correspond to a DCM, which also suggest a significant biological source
of H
2
O
2
(Sarthou et al.
1997
; Croot et al.
2005
). The decay of H
2
O
2
apparently fol-
lows first-order kinetics (Petasne and Zika
1997
; Yuan and Shiller
2001
) and is bio-
logically mediated by small microorganisms (Petasne and Zika
1997
).
Filtration of seawater to remove the biota typically produces a dramatic reduc-
tion in the decay rate of H
2
O
2
(Moffett and Zafiriou
1990
; Petasne and Zika
1997
;
Fujiwara et al.
1993
), whilst the amount of colloidal material influences the decay
rate (Yuan and Shiller
2001
). H
2
O
2
may be concentrated by particulate organic
matter or small fungi through rapid transpiration (Komissarov
1994
,
1995
,
2003
).
The decay process of H
2
O
2
can be explained in two ways: one is the uptake possi-
ble of H
2
O
2
by microorganisms during photosynthesis, the other is the decomposi-
tion of H
2
O
2
by catalases and peroxidases bound to microorganisms. Catalases and
peroxidase can enzymatically activate H
2
O
2
to detoxify it to H
2
O (see also chap-
Peroxides in Natural Waters
”) (Moffett and Zafiriou
1990
). Moreover, conversion of
H
2
O
2
to H
2
O by catalases and peroxidases could play a key role in photosynthesis
and needs further study to clarify the possible links. Note that dark reduction of CO
2
may take place because of the electrons that are released by organic molecules and
sulfide (Jagannathan and Golbeck
2009
). Some important phenomena relevant to this
context are extensively discussed in the photosynthesis chapter (
“
Photosynthesis in
3.3 Changes in the Chl
a
Concentrations in Natural Waters
Chl
a
concentrations undergo significant variations in the water column, which
can be seasonal, spatial and temporal depending on various factors that charac-
terize water (Bianchi et al.
2002
; Sommaruga and Augustin
2006
; Biggs
2000
;
de Moraes Novo et al.
2006
; Duan and Bianchi
2006
; Lewis et al.
2010
).
Streams and Rivers
Chl
a
concentrations range from 0.0 to 280
μ
g L
−
1
in streams and rivers (Table
1
)
(Miltner
2010
; Chessman
1985
; Lohman and Jones
1999
; van Nieuwenhuyse and
Jones
1996
; Basu and Pick
1997
; Gao et al.
2004
; Guéguen et al.
2006
; Morgan
et al.
2006
; Devercelli and Peruchet
2008
; Palmer-Felgate et al.
2008
; Royer
et al.
2008
; Longing and Haggard
2010
; Calijuri et al.
2008
). The highest Chl
a
concentrations in freshwater riverine ecosystems are in the order of <280
μ
g L
−
1
in River Alne (Warwickshire, UK); <263
μ
g L
−
1
in Red River and its basin (USA);
<240
μ
g L
−
1
in River Arrow (Warwickshire, UK); <216
μ
g L
−
1
in Paraná River
basin (South America); <170
μ
g L
−
1
in temperate streams (USA); <100
μ
g L
−
1
