384
Chapter 11: The Pacific Ocean
southeasterly monsoon, and reveal major meandering plumes of high chlorophyll that
extend out from the coast to the central region of the South China Sea.
Of course, the generally limiting nutrient in the South China Sea is again nitrate and so
Trichodesmium is, as in the Coral Sea, a major component of the planktonic autotrophs;
this organism is, of course, most frequently phosphate-limited and it may be that the
effluents of Mekong and other great rivers draining into the South China Sea carry
enough of this element to the surface waters to ensure massive and sustained blooms of
Trichodesmium as occurs in the Guiana Current far downstream from the Amazon plume
(Lenes et al., 2005). The diatom symbiont Richelia intracellularis makes some contribution
to nitrogen acquisition by the phytoplankton in the South China Sea, although probably
< 5% of that which is based on nitrate flux across the nutricline during the winter
monsoon (Chen et al., 2004). The picoplankton of the DCM is increasingly dominated by
Prochlorococcus toward the central regions, away from the shelf. The Celebes Sea appears
to have a very similar pattern of phytoplankton ecology to the South China Sea with
near-surface abundance of diatoms (with Richelia?) and Trichodesmium as well as a
cyanobacteria-dominated DCM that is associated with a microzooplankton maximum.
Synopsis
Case 3—Winter-spring production with nutrient limitation—The climatological seasonal
cycles of chlorophyll and productivity offered for this province (Fig. 11.15) are somewhat
misleading, because they are dominated by seasonality near the equator and further south.
The pycnocline undergoes a weak seasonal excursion (20 m November–April in northerly
0
20
40
60
80
100
0
5
10
15
20
25
Climatology (years)
Depth (m)
Production at DCM (%)
Zm (sigma)
Zeu
Pt (at DCM)
0.20
0.24
0.28
0.32
0.36
0.40
0.12
0.16
0.20
0.24
0.28
SeaWiFS (ARCH): September 1997 - January 2002
Surface Chl (mg m
-3
)
Pt (gC m
-2
d
-1
)
Pt d
-1
Chl m
-3
1998
1999
2000
2001
Fig. 11.15 ARCH: seasonal cycles of monthly surface chlorophyll and depth-integrated autotrophic production
for the years 1997–2002 from SeaWiFS data together with characteristic seasonal cycles of mixed-layer depths
from Levitus climatological data and photic depths computed from characteristic irradiance and the archive
of chlorophyll profiles discussed in Chapter 1.
Chapter 11: The Pacific Ocean
southeasterly monsoon, and reveal major meandering plumes of high chlorophyll that
extend out from the coast to the central region of the South China Sea.
Of course, the generally limiting nutrient in the South China Sea is again nitrate and so
Trichodesmium is, as in the Coral Sea, a major component of the planktonic autotrophs;
this organism is, of course, most frequently phosphate-limited and it may be that the
effluents of Mekong and other great rivers draining into the South China Sea carry
enough of this element to the surface waters to ensure massive and sustained blooms of
Trichodesmium as occurs in the Guiana Current far downstream from the Amazon plume
(Lenes et al., 2005). The diatom symbiont Richelia intracellularis makes some contribution
to nitrogen acquisition by the phytoplankton in the South China Sea, although probably
< 5% of that which is based on nitrate flux across the nutricline during the winter
monsoon (Chen et al., 2004). The picoplankton of the DCM is increasingly dominated by
Prochlorococcus toward the central regions, away from the shelf. The Celebes Sea appears
to have a very similar pattern of phytoplankton ecology to the South China Sea with
near-surface abundance of diatoms (with Richelia?) and Trichodesmium as well as a
cyanobacteria-dominated DCM that is associated with a microzooplankton maximum.
Synopsis
Case 3—Winter-spring production with nutrient limitation—The climatological seasonal
cycles of chlorophyll and productivity offered for this province (Fig. 11.15) are somewhat
misleading, because they are dominated by seasonality near the equator and further south.
The pycnocline undergoes a weak seasonal excursion (20 m November–April in northerly
0
20
40
60
80
100
0
5
10
15
20
25
Climatology (years)
Depth (m)
Production at DCM (%)
Zm (sigma)
Zeu
Pt (at DCM)
0.20
0.24
0.28
0.32
0.36
0.40
0.12
0.16
0.20
0.24
0.28
SeaWiFS (ARCH): September 1997 - January 2002
Surface Chl (mg m
-3
)
Pt (gC m
-2
d
-1
)
Pt d
-1
Chl m
-3
1998
1999
2000
2001
Fig. 11.15 ARCH: seasonal cycles of monthly surface chlorophyll and depth-integrated autotrophic production
for the years 1997–2002 from SeaWiFS data together with characteristic seasonal cycles of mixed-layer depths
from Levitus climatological data and photic depths computed from characteristic irradiance and the archive
of chlorophyll profiles discussed in Chapter 1.