232
Chapter 9: The Atlantic Ocean
community dominated down to midshelf depths. At only four stations close to the mouth
of the Gambia River, in slightly muddier sediments, was an Amphioplus community
found. A very reduced deep shelf community, rich in pennatularians and sharing many
other species with the same association in the Gulf of Guinea, extended from 75–80 m
down to the shelf break.
Not only is the species composition of the macrobenthos of this province a function
of depth and sediment type, but so also is the species composition of the demersal fish
community. The deep sparid community, which will be introduced in the account of the
GUIN province, typically occupies the shelly and sandy grounds of the continental shelf
the length of the African coast from north of Cape Verde right up to the Mediterranean.
Dominant species are Dentex canariensis and D. filosus, Pagrus ehrenbergi, and species of
Upenaeus, Smaris, Lepidotrigla, and Brotula.
Synopsis
Case 6—Intermittent production at coastal divergences—The synopsis of archived data
offered in Fig. 9.23 does not represent any single upwelling cell. Rather, all upwelling cells
have shorter upwelling seasons than is suggested by the integrated data, which best fit
the central region from 20
N to 25
N. General seasonality of Z m is consistent with both
boreal winter mixing (50 m January–February) and summer stratification and upwelling
(20 m August–September). Because Z eu remains between 50 and 70 m in all months, the
thermocline is illuminated except for 5 months in boreal winter, and presumably also in
0
20
40
60
80
100
0
0.1
0.2
0.3
0.4
0.5
Climatology (years)
Depth (m)
Production at DCM (%)
Zm (sigma)
Zeu
Pt (at DCM)
0.00
0.30
0.60
0.90
1.20
1.50
0.00
0.50
1.00
1.50
2.00
2.50
SeaWiFS (CNRY): September 1997 - January 2002
Surface Chl (mg m -3
)
Pt d
-1
Chl m
-3
1999
2000
2001
2002
Pt (gC m
-2
d
-1
)
Fig. 9.23 CNRY: 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 9: The Atlantic Ocean
community dominated down to midshelf depths. At only four stations close to the mouth
of the Gambia River, in slightly muddier sediments, was an Amphioplus community
found. A very reduced deep shelf community, rich in pennatularians and sharing many
other species with the same association in the Gulf of Guinea, extended from 75–80 m
down to the shelf break.
Not only is the species composition of the macrobenthos of this province a function
of depth and sediment type, but so also is the species composition of the demersal fish
community. The deep sparid community, which will be introduced in the account of the
GUIN province, typically occupies the shelly and sandy grounds of the continental shelf
the length of the African coast from north of Cape Verde right up to the Mediterranean.
Dominant species are Dentex canariensis and D. filosus, Pagrus ehrenbergi, and species of
Upenaeus, Smaris, Lepidotrigla, and Brotula.
Synopsis
Case 6—Intermittent production at coastal divergences—The synopsis of archived data
offered in Fig. 9.23 does not represent any single upwelling cell. Rather, all upwelling cells
have shorter upwelling seasons than is suggested by the integrated data, which best fit
the central region from 20
N to 25
N. General seasonality of Z m is consistent with both
boreal winter mixing (50 m January–February) and summer stratification and upwelling
(20 m August–September). Because Z eu remains between 50 and 70 m in all months, the
thermocline is illuminated except for 5 months in boreal winter, and presumably also in
0
20
40
60
80
100
0
0.1
0.2
0.3
0.4
0.5
Climatology (years)
Depth (m)
Production at DCM (%)
Zm (sigma)
Zeu
Pt (at DCM)
0.00
0.30
0.60
0.90
1.20
1.50
0.00
0.50
1.00
1.50
2.00
2.50
SeaWiFS (CNRY): September 1997 - January 2002
Surface Chl (mg m -3
)
Pt d
-1
Chl m
-3
1999
2000
2001
2002
Pt (gC m
-2
d
-1
)
Fig. 9.23 CNRY: 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.