Environmental Engineering Reference
In-Depth Information
relatively low (0.19-0.43
μ
g L
−
1
) in the presence of rather elevated amounts of NH
4
+
(22.55-29.50
μ
M), and PO
4
3
−
(1.71-2.35
μ
M), even in the
presence of similar water temperatures (Table
1
) (Verlencar et al.
1990
). This result
can imply that nutrients have limited influence on photosynthesis in offshore seawater.
A more important effect could be that high contents of algae (or phytoplankton spe-
cies) in coastal Antarctic seawater ice can absorb irradiance by Chl
a
bound to PSI
and PSII. A possible consequence would be intracellular or extracellular H
2
O
2
for-
mation, which could directly affect photosynthesis. This effect could be more impor-
tant in coastal seawater ice than in offshore oceanic seawater ice. The covariation of
dissolved nitrate and phosphate maintained by ocean circulation (Weber and Deutsch
2010
) might be a factor that affects photosynthesis in offshore regions. However,
future studies will be required to provide evidence for this mechanism.
−
(0.14-1.36
μ
M), NO
3
4 Factors Controlling Chl
a
in Natural Waters
There are a numbers of environmental factors that substantially influence Chl
a
concentrations or primary production in natural waters. The key factors affecting
photosynthetic and respiratory activities can be detected based on the growth and
development of organisms. They are: (i) seasonal variation in sunlight and UV
radiation, which affect photosynthesis; (ii) occurrence of CO
2
forms; (iii) varia-
tion in temperature; (iv) effects of water stress (drought) and precipitation/rainfall;
(v) effects of the amount and nature of DOM and POM; (vi) variation in nutrient
contents; (vii) variation in trace metal ions; (viii) effect of salinity or salt stress;
(ix) effects of toxic pollutants on aquatic microorganisms; (x) effect of size-frac-
tionated phytoplankton; (xi) effects of global warming. These factors are similar
to those affecting primary production or cyanobacterial bloom, which the excep-
tion of the effect of global warming (see chapter
“
Photosynthesis in Nature:
Natural Waters
”
).
4.1 Effects of Global Warming
Global warming can affect the heat budget and other physical processes of a water
body, and can subsequently alter the stratification and mixed layer depths (Huisman
et al.
2006
; Schindler
1997
; Magnuson et al.
1997
). Such changes, along with
global warming-induced changes in the seasonal light cycle, can alter the sea-
sonal patterns of Chl contents (or primary production), phytoplankton composition
and nutrient concentrations in SCM and DCM (Huisman et al.
2006
; Walsby et al.
1997
; O'Reilly et al.
2003
; Verburg et al.
2003
; Baulch et al.
2005
; Fu et al.
2007
;
Jöhnk et al.
2008
; Castle and Rodgers
2009
; Davis et al.
2009
; Paerl and Huisman
2009
). Correspondingly, an extension of the summer season due to global warming
