Indian Ocean Coastal Biome
319
The coral reefs in the equatorial section of this province, off Kenya and Tanzania,
suffered extreme heat stress and bleaching during the second half of 1998, 60–80% of live
corals being lost in shallow areas; coral recovery is unexpectedly slow, due to removal of
herbivorous fish by artisanal fishing and hence the proliferation of fleshy algae over the
reefs. The fishing pressure on these reefs, near centers of population, is intense especially
for spiny lobsters (Panulirus spp.). These, and several warm-water shrimps (Penaeidae),
form an important part of the mobile benthic fauna of this province, at least as far as
∼5
S; otherwise, this warm-water region supports a demersal fish fauna typical of tropical
shelves—dominated by sciaenids (Otolithes rubra and others), together with Thryssa,
Pomadasys, Arius, Pellona, Trichiurus—and so on.
Synopsis
Case 4—Small-amplitude response to trade-wind seasonality—Here, the integration of the
whole area in satellite chlorophyll data is not very satisfactory because of the great latitudinal extent of the province; as Fig. 10.8 shows, this suggests a rather simple cycle with
maximal productivity in December–February (austral summer) and maximal biomass
in June–August (austral winter). Mixed-layer Z m undergoes an austral winter excursion
from 15 m (summer) to 60 m in June–July, forced by wind mixing in the south, and
westward thermocline tilt in the tropical region. The pycnocline is illuminated only in
boreal summer, June–September. There are very striking opposite seasonal trends in
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)
0.00
0.20
0.40
0.60
0.80
1.00
0.15
0.20
0.25
0.30
0.35
0.40
SeaWiFS (EAFR): September 1997 - January 2002
Surface Chl (mg m -3
)
Pt d
-1
Chl m
-3
1998
1999
2000
2001
Pt (gC m
-2
d
-1
)
Fig. 10.8 EAFR: 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.
319
The coral reefs in the equatorial section of this province, off Kenya and Tanzania,
suffered extreme heat stress and bleaching during the second half of 1998, 60–80% of live
corals being lost in shallow areas; coral recovery is unexpectedly slow, due to removal of
herbivorous fish by artisanal fishing and hence the proliferation of fleshy algae over the
reefs. The fishing pressure on these reefs, near centers of population, is intense especially
for spiny lobsters (Panulirus spp.). These, and several warm-water shrimps (Penaeidae),
form an important part of the mobile benthic fauna of this province, at least as far as
∼5
S; otherwise, this warm-water region supports a demersal fish fauna typical of tropical
shelves—dominated by sciaenids (Otolithes rubra and others), together with Thryssa,
Pomadasys, Arius, Pellona, Trichiurus—and so on.
Synopsis
Case 4—Small-amplitude response to trade-wind seasonality—Here, the integration of the
whole area in satellite chlorophyll data is not very satisfactory because of the great latitudinal extent of the province; as Fig. 10.8 shows, this suggests a rather simple cycle with
maximal productivity in December–February (austral summer) and maximal biomass
in June–August (austral winter). Mixed-layer Z m undergoes an austral winter excursion
from 15 m (summer) to 60 m in June–July, forced by wind mixing in the south, and
westward thermocline tilt in the tropical region. The pycnocline is illuminated only in
boreal summer, June–September. There are very striking opposite seasonal trends in
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)
0.00
0.20
0.40
0.60
0.80
1.00
0.15
0.20
0.25
0.30
0.35
0.40
SeaWiFS (EAFR): September 1997 - January 2002
Surface Chl (mg m -3
)
Pt d
-1
Chl m
-3
1998
1999
2000
2001
Pt (gC m
-2
d
-1
)
Fig. 10.8 EAFR: 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.