Environmental Engineering Reference
In-Depth Information
contents of organic matter (DOM and POM) in coastal waters are responsible for
the higher observed contents of Chl
a
compared to the open ocean (Clark et al.
2004
). It is generally known that DOM and POM (e.g. phytoplankton) can release
NO
3
and PO
4
3
−
, by either photoinduced or microbial assimilation/respiration in
waters (see chapters
“
Dissolved Organic Matter in Natural Waters
,
Photoinduced
(ii) Strong wind and wave mixing along with the solar (UV and PAR) radiation
may degrade Chl
a
, DNA or biomolecules bound to PSI and PSII of microorgan-
isms. The effect would be more marked in the open ocean compared to coastal
waters. This issue would be supported by the observation that UV-B radiation
(280-315 nm) can inhibit photosynthetic carbon fixation by tropical phytoplankton
assemblages in coastal to pelagic surface seawaters (Li et al.
2011
). The inhibition
of photosynthesis by UV-A (315-400 nm) increases from coastal to offshore waters
(Li et al.
2011
). It has also been shown that UV-B inhibits photosynthesis by up to
27 % and UV-A by up to 29 % (Li et al.
2011
). In East China Sea, lower concen-
tration of Chl
a
(0.06-0.07
μ
g L
−
1
: Kuroshio sites) has been detected in the open
ocean, with high water temperature (23.9-24.0 °C) and low NO
3
−
−
(<0.1
μ
M), than
in coastal seawater (0.43-2.44
μ
g L
−
1
) (Hung et al.
2000
). The latter had low tem-
perature (16.3-18.9 °C) and high NO
3
−
(<0.4-6.0
μ
M) (Hung et al.
2000
).
Similarly and interestingly, Chl
a
concentrations are largely variable (0.06-
1,000
μ
g L
−
1
) and substantially high (occasionally >1,000
μ
g L
−
1
) in ice-covered
Antarctic and Arctic Oceans (Table
1
) (Palmisano et al.
1985
; Garrison et al.
1986
;
Wheeler et al.
1996
; Mock and Gradinger
1999
; Apollonio
1980
; Guildford and
Hecky
2000
; Norrbin et al.
2009
; Sakshaug and Holm-Hansen
1986
; Spies
1987
;
Verlencar et al.
1990
; Varela et al.
2002
; Cottrell and Kirchman
2009
; Hewes et
al.
2009
). The highest Chl
a
concentrations, reaching values higher than 1,000
μ
g
L
−
1
, have been detected in bottom-ice communities of Antarctica Ocean.
Otherwise, Chl
a
is largely variable: it reached <297
μ
g L
−
1
in the ice undersur-
face; <5.2 in the water column of central Arctic Ocean; <86
μ
g L
−
1
in Barents and
Greenland Sea ice (Arctic Ocean); <25
μ
g L
−
1
in Gerlache and south Bransfield
Straits (Antarctic Peninsula); <8.2
μ
g L
−
1
in Dumbell Bay (Arctic Ocean);
<4.03
μ
g L
−
1
in ocean seawater (Antarctic Ocean); <4.0
μ
g L
−
1
in South Shetland
Islands (Antarctica), 0.10-2.27 in other ice seawater; and finally 111
±
30
μ
g L
−
1
in incubation experimental studies using Antarctic ice seawater (Table
1
).
It has been shown that Chl
a
varies significantly, from 0.1 to 297
μ
g L
−
1
in ice
undersurface and from 0.1 to 5.2
μ
g L
−
1
in the water column (Wheeler et al.
1996
).
The values of Chl
a
can increase in the range of the potential phytoplankton stand-
ing stock (25-50
μ
g L
−
1
) in Antarctic marine waters, Southern Ocean (Sakshaug
and Holm-Hansen
1986
; Spies
1987
). Similarly, Chl
a
contents in bottom ice com-
munities reach 300-400 mg m
−
2
(Steemann-Nielsen
1962
; Palmisano and Sullivan
1983
). Such numerous algal communities are presumably the consequence of sev-
eral phenomena: (i) Algal growth may be prolonged due to low temperature and low
solar irradiance, which are unable to form O
2
•
−
and subsequently H
2
O
2
or HO
•
. This
phenomenon can protect algal cells from death, allowing high primary production
