Environmental Engineering Reference
In-Depth Information
Biogeochemical Cycles in Natural Waters
”) (Mostofa et al.
2009
; Mostofa and
Sakugawa
2009
; Zhang et al.
2009
; Tranvik et al.
2009
; Zepp et al.
1987
,
2011
;
Mostofa et al.
2011
; Graneli et al.
1996
; Granéli et al.
1998
; Ma and Green
2004
;
White et al.
2010
; Liu et al.
2010
; Fu et al.
2010
; Palenik et al.
1987
; Cooper and
Lean
1992
; Bushaw et al.
1996
; Molot et al.
2005
; Kim et al.
2006
; Johannessen et
al.
2007
; Borges et al.
2008
; Li et al.
2008
; Kujawinski et al.
2009
; Lohrenz et al.
2010
; Omar et al.
2010
; Cai
2011
). Such processes can influence photosynthesis
directly or indirectly in water.
Photoinduced degradation of DOM and POM (POM includes e.g. phytoplank-
ton) can be summarized as follows (Eq.
5.29
):
DOM
+
POM
+
h
υ →
H
2
O
2
+
CO
2
+
DIC
+
LOW DOM
+
NO
3
−
+
NO
2
−
+
PO
3
−
4
(5.29)
+
autochthonous DOM
+
other species
where DIC is usually defined as the sum of an equilibrium mixture of dissolved
CO
2
,H
2
CO
3
, HCO
3
−
, AND CO
2
−
.
3
Microbial degradation of DOM and POM could be indicated as (
5.30
):
DOM
+
POM
+
microbes
→
H
2
O
2
+
CO
2
+
DIC
+
LOW DOM
+
NO
3
−
+
PO
3
−
(5.30)
+
autochthonous DOM
+
other species
4
CO
2
, DIC, and nutrients (NO
3
and PO
4
3
−
) are primarily responsible for an
increase in photosynthetic efficiency in water (Eq.
3.1
). Therefore photosynthesis
depends on the contents and chemical nature of allochthonous OM (of terrestrial
vascular plant origin) and autochthonous OM (of algal or phytoplankton origin).
They are characterized by a large variation in different water environments (see
chapter
“
Dissolved Organic Matter in Natural Waters
”
). Dependence of photosyn-
thesis on OM (DOM and POM) is supported by several observation reported below.
First, DOM contents can affect photosynthesis in the water column. DOM can
limit productivity and affect epilimnetic and hypolimnetic respiration (Jackson
and Hecky
1980
; Carpenter et al.
1998
; Hanson et al.
2003
; Houser et al.
2003
;
Druon et al.
2010
). Both DOM and POM can limit light penetration in deeper
water, thus shoaling the euphotic zone (Bertilsson and Tranvik
2000
; Laurion
et al.
2000
; Hayakawa and Sugiyama
2008
; Effler et al.
2010
). The vertical attenu-
ation coefficient for downward irradiance of PAR (
K
PA R
) is strongly dependent on
water color (Eloranta
1978
; Jones and Arvola
1984
), which subsequently depends
on DOC concentration (Jones and Arvola
1984
). Elevated DOM may decrease the
efficiency of photosynthesis and growth in deeper waters and produce surface Chl
−
