zero to 0.5 ml of O 2 per liter of seawater, or <45 mmol/kg
(Helly and Levin, 2004; Fiedler and Talley, 2006;
Stramma et al., 2008). The pH of the region is lower compared to other tropical regions (Feely et al., 2004; Orr
et al., 2005; Kleypas et al., 2006), especially during the
seasonal upwellings.
El Niño-Southern Oscillation (ENSO) is an ocean–
atmosphere phenomenon generated in the Eastern Pacific,
with significant climatic and economic impacts worldwide (Glantz, 2001). During an ENSO event, the water
temperature of the ETP rises, resulting in some cases,
especially in the last two decades, in the mass mortality
of corals and other marine organisms (Enfield, 1989;
Glynn, 1990; Wang and Fiedler, 2006).
In summary, the ocean dynamics of the ETP depend
on the large-scale ocean circulation with seasonal modifications due to wind variations and the displacement of
the ITCZ. On a longer time scale, ENSO events play
a significant role in the ocean dynamics and distribution
of the biota of the ETP (Fiedler and Talley, 2006; Wang
and Fiedler, 2006; Lizano, 2008).
Coral reefs
Geological history
The geological history of ETP coral reefs started after the
closure of the Central American Isthmus some three million years ago (Coates et al., 1992). Before that, the waters
of what is now the ETP were connected to the present day
Caribbean Sea, sharing flora and fauna (Stehli and Webb,
1985; D’Croz and Robertson, 1997). The ETP is now one
of the most isolated ocean regions of the world, separated
from the Central Pacific by the East Pacific Barrier. This
vast expanse of deep water has been an effective barrier
to dispersal of tropical shallow-water organisms throughout the Cenozoic (Cortés, 1986; Grigg and Hey, 1992;
Glynn and Ault, 2000). The main currents in the ETP are
from east to west, the north and south Equatorial Currents
(Glynn et al., 1996; Fiedler and Talley, 2006; Lizano,
2008). However, the weaker but nevertheless important
North Equatorial Countercurrent can transport organisms
to the Eastern Pacific from the Central and Western Pacific
(Scheltema, 1988; Richmond, 1990; Glynn et al., 1996).
After the closure of the Central American Seaway, all
Caribbean reef-building corals in the ETP became extinct
and were substituted by Indo-Pacific species (Dana, 1975;
Cortés, 1986; Glynn, 1997). At present, there are five genera shared but not a single species of reef-building corals
in common between the Caribbean and the ETP (Cortés,
2003). Other marine groups in the ETP also show this
Indo-Pacific affinity, including mollusks (Scheltema,
1988), echinoderms (Lessios et al., 1998), and fishes
(Robertson and Cramer, 2009).
With the closure of the Central American Seaway,
oceanographic conditions profoundly changed in the
ETP (D’Croz and Robertson, 1997). Now, El Niño could
develop bringing warm waters to the region (Enfield,
1989), and the seasonal upwellings off the low lands of
Mesoamerica bring cold waters to the region (Glynn
et al., 1983; Willet et al., 2006). The ETP is also
a pocket of low-salinity and low-pH waters as compared
to other oceans (Fieldler and Talley, 2006; Kleypas et al.,
2006; Lizano, 2008). All these conditions are inimical
for reef development and consolidation (Cortés, 1997;
Manzello et al., 2008). Additionally, there were significant
changes to oceanic circulation with the closure of the Central American Isthmus.
The continental shelfs of ETP are narrow and drop
abruptly to a deep seafloor with some seamounts and
ridges (e.g., Carnegie and Cocos). The narrowness of the
shelf contributes to the limited development of coral reefs
in the region. Cortés (1986) suggested that during the low
sea level stands in the Holocene significantly reduced the
area where coral reefs could develop. This, combined
with the changing oceanographic conditions in the ETP
after the closure of the Central America Seaway, resulted
in the elimination of most corals reefs in the region and
allowed subsequent replenishment from the Western
Pacific.
Holocene growth history
Extant coral reef growth in the ETP started around 5,600
years BP (Glynn and Macintyre, 1977; Cortés et al.,
1994). In Panamá, the dominant reef-framework builders
are pocilloporid corals, mainly Pocillopora damicornis.
Reef growth ranges from 1.3 to 4.2 m/1,000 years in the
reef flat to 7.5 m/1,000 years in the reef front. Mean maximum reef thickness was higher in the non-upwelling
region (Gulf of Chiriquí: 8.3 m, with a maximum of
13 m) than in the upwelling Gulf of Panama (4.2 m)
(Glynn and Macintyre, 1977).
At Punta Islotes in Golfo Dulce, Costa Rica, the initial
phase of reef growth was by pocilloporids, which created
a substrate over sandy bottoms on which Porites lobata
grew, the dominant reef-frame builder in this location.
During the first 3,000 years, growth was slow, but
between 2,500 and 500 year BP reef structure growth
was extremely fast, in the order of 5–8.3 m/1,000 years,
attaining reef framework thickness of up to 9 m (Cortés
et al., 1994). At around 500 year BP, there was a significant increase in fresh water in Golfo Dulce. Tectonic
movements altered the watersheds, and two large rivers
started flowing into the inner section of the gulf where
the reefs were growing (Cortés, 1990). This slowed reef
accretion, and about 60 years ago reef growth completely
stopped when there was an increase in terrigenous sedimentation as a result of the removal of the forest for
banana plantations. Sediments loads are still high due to
deforestation, inappropriate agricultural practices, coastal
alteration, and road construction in the gulf’s watershed.
Coral reef growth off the coasts of Panamá and Costa
Rica has resulted in thick reef structures (up to 13 m),
while in offshore islands (Isla del Caño and Isla del Coco,
Costa Rica; and the Galápagos Islands, Ecuador) the
reef framework is only a thin veneer of corals over
EASTERN TROPICAL PACIFIC CORAL REEFS
353
(Helly and Levin, 2004; Fiedler and Talley, 2006;
Stramma et al., 2008). The pH of the region is lower compared to other tropical regions (Feely et al., 2004; Orr
et al., 2005; Kleypas et al., 2006), especially during the
seasonal upwellings.
El Niño-Southern Oscillation (ENSO) is an ocean–
atmosphere phenomenon generated in the Eastern Pacific,
with significant climatic and economic impacts worldwide (Glantz, 2001). During an ENSO event, the water
temperature of the ETP rises, resulting in some cases,
especially in the last two decades, in the mass mortality
of corals and other marine organisms (Enfield, 1989;
Glynn, 1990; Wang and Fiedler, 2006).
In summary, the ocean dynamics of the ETP depend
on the large-scale ocean circulation with seasonal modifications due to wind variations and the displacement of
the ITCZ. On a longer time scale, ENSO events play
a significant role in the ocean dynamics and distribution
of the biota of the ETP (Fiedler and Talley, 2006; Wang
and Fiedler, 2006; Lizano, 2008).
Coral reefs
Geological history
The geological history of ETP coral reefs started after the
closure of the Central American Isthmus some three million years ago (Coates et al., 1992). Before that, the waters
of what is now the ETP were connected to the present day
Caribbean Sea, sharing flora and fauna (Stehli and Webb,
1985; D’Croz and Robertson, 1997). The ETP is now one
of the most isolated ocean regions of the world, separated
from the Central Pacific by the East Pacific Barrier. This
vast expanse of deep water has been an effective barrier
to dispersal of tropical shallow-water organisms throughout the Cenozoic (Cortés, 1986; Grigg and Hey, 1992;
Glynn and Ault, 2000). The main currents in the ETP are
from east to west, the north and south Equatorial Currents
(Glynn et al., 1996; Fiedler and Talley, 2006; Lizano,
2008). However, the weaker but nevertheless important
North Equatorial Countercurrent can transport organisms
to the Eastern Pacific from the Central and Western Pacific
(Scheltema, 1988; Richmond, 1990; Glynn et al., 1996).
After the closure of the Central American Seaway, all
Caribbean reef-building corals in the ETP became extinct
and were substituted by Indo-Pacific species (Dana, 1975;
Cortés, 1986; Glynn, 1997). At present, there are five genera shared but not a single species of reef-building corals
in common between the Caribbean and the ETP (Cortés,
2003). Other marine groups in the ETP also show this
Indo-Pacific affinity, including mollusks (Scheltema,
1988), echinoderms (Lessios et al., 1998), and fishes
(Robertson and Cramer, 2009).
With the closure of the Central American Seaway,
oceanographic conditions profoundly changed in the
ETP (D’Croz and Robertson, 1997). Now, El Niño could
develop bringing warm waters to the region (Enfield,
1989), and the seasonal upwellings off the low lands of
Mesoamerica bring cold waters to the region (Glynn
et al., 1983; Willet et al., 2006). The ETP is also
a pocket of low-salinity and low-pH waters as compared
to other oceans (Fieldler and Talley, 2006; Kleypas et al.,
2006; Lizano, 2008). All these conditions are inimical
for reef development and consolidation (Cortés, 1997;
Manzello et al., 2008). Additionally, there were significant
changes to oceanic circulation with the closure of the Central American Isthmus.
The continental shelfs of ETP are narrow and drop
abruptly to a deep seafloor with some seamounts and
ridges (e.g., Carnegie and Cocos). The narrowness of the
shelf contributes to the limited development of coral reefs
in the region. Cortés (1986) suggested that during the low
sea level stands in the Holocene significantly reduced the
area where coral reefs could develop. This, combined
with the changing oceanographic conditions in the ETP
after the closure of the Central America Seaway, resulted
in the elimination of most corals reefs in the region and
allowed subsequent replenishment from the Western
Pacific.
Holocene growth history
Extant coral reef growth in the ETP started around 5,600
years BP (Glynn and Macintyre, 1977; Cortés et al.,
1994). In Panamá, the dominant reef-framework builders
are pocilloporid corals, mainly Pocillopora damicornis.
Reef growth ranges from 1.3 to 4.2 m/1,000 years in the
reef flat to 7.5 m/1,000 years in the reef front. Mean maximum reef thickness was higher in the non-upwelling
region (Gulf of Chiriquí: 8.3 m, with a maximum of
13 m) than in the upwelling Gulf of Panama (4.2 m)
(Glynn and Macintyre, 1977).
At Punta Islotes in Golfo Dulce, Costa Rica, the initial
phase of reef growth was by pocilloporids, which created
a substrate over sandy bottoms on which Porites lobata
grew, the dominant reef-frame builder in this location.
During the first 3,000 years, growth was slow, but
between 2,500 and 500 year BP reef structure growth
was extremely fast, in the order of 5–8.3 m/1,000 years,
attaining reef framework thickness of up to 9 m (Cortés
et al., 1994). At around 500 year BP, there was a significant increase in fresh water in Golfo Dulce. Tectonic
movements altered the watersheds, and two large rivers
started flowing into the inner section of the gulf where
the reefs were growing (Cortés, 1990). This slowed reef
accretion, and about 60 years ago reef growth completely
stopped when there was an increase in terrigenous sedimentation as a result of the removal of the forest for
banana plantations. Sediments loads are still high due to
deforestation, inappropriate agricultural practices, coastal
alteration, and road construction in the gulf’s watershed.
Coral reef growth off the coasts of Panamá and Costa
Rica has resulted in thick reef structures (up to 13 m),
while in offshore islands (Isla del Caño and Isla del Coco,
Costa Rica; and the Galápagos Islands, Ecuador) the
reef framework is only a thin veneer of corals over
EASTERN TROPICAL PACIFIC CORAL REEFS
353