Eastern Pacific Coral Reef Ecosystem
285
where nearshore surface salinities are 30 psu ( ~o/oo) or lower at the height
of the rainy season.
19.3 The Eastern Pacific Coral Reef Region
With the closure of the Central American seaway, about 3.5-3 Ma (Coates
and Obando 1996), former connections between the tropical marine biota
of the eastern Pacific, Indo-Pacific and western Caribbean Sea were severed for the last time. During earlier geologic time, between 18 and 14 Ma,
the western portion of the circumtropical Tethys Sea became separated
from the Atlantic Ocean by the emergence of a land corridor resulting from
the collision of the African plate and southern India with Eurasia. Since
this separation the species composition, ecological processes and structure
of amphi-American coral reef communities have changed radically (Glynn
1982). The eastern Pacific region is now an impoverished outpost of the
central and western Pacific coral reef domain and no longer shares any
reef-building coral species with the Atlantic region. A total of 69 western
Atlantic and 534 west/central Pacific coral species have been described. As
many as 30 to 40 coral species are found on any given Caribbean reef and
twice this number or more on most west/central Pacific reefs. By contrast,
known eastern Pacific zooxanthellate corals (scleractinians and hydrocorals in the genus Millepora) number 41 species with about 10 species
occupying any particular site where they contribute more or less significantly toward reef building. Branching coral colonies in the genus Pocillopora, specifically Pocillopora damicornis (Linnaeus) and Pocillopora elegans Dana, are preeminent in reef building, forming intermeshing
compact frameworks not uncommonly attaining 2-3m in relief. Species
with massive, dome-shaped colony morphologies, such as Porites lobata
Dana, Pavona clavus Dana and Pavona gigantea Verrill, can also sometimes build mono- to paucispecific reef frameworks or contribute to pocilloporid reef building. Remarkably, these examples demonstrate that only
one or a few coral species are capable of building coral reefs.
Marginal coral framework development has been reported at Cabo
Pulmo-Los Frailes off SE Baja California (Fig. 19.1, site 1), and some of the
coral communities in this area accommodate a diverse alcyonarian fauna.
Fringing coral reefs occur in the Nayarit area and coral communities are
present at Bahia Banderas, which experiences local upwelling (Fig. 19.1,
site 2; Fig. 19.2A; Reyes Bonilla 1993; Carriquiry and Reyes Bonilla 1997).
Upwelling here is intensified topographically by a submarine canyon that
approaches close to the coast. Possibly one of the largest coral reefs in the
285
where nearshore surface salinities are 30 psu ( ~o/oo) or lower at the height
of the rainy season.
19.3 The Eastern Pacific Coral Reef Region
With the closure of the Central American seaway, about 3.5-3 Ma (Coates
and Obando 1996), former connections between the tropical marine biota
of the eastern Pacific, Indo-Pacific and western Caribbean Sea were severed for the last time. During earlier geologic time, between 18 and 14 Ma,
the western portion of the circumtropical Tethys Sea became separated
from the Atlantic Ocean by the emergence of a land corridor resulting from
the collision of the African plate and southern India with Eurasia. Since
this separation the species composition, ecological processes and structure
of amphi-American coral reef communities have changed radically (Glynn
1982). The eastern Pacific region is now an impoverished outpost of the
central and western Pacific coral reef domain and no longer shares any
reef-building coral species with the Atlantic region. A total of 69 western
Atlantic and 534 west/central Pacific coral species have been described. As
many as 30 to 40 coral species are found on any given Caribbean reef and
twice this number or more on most west/central Pacific reefs. By contrast,
known eastern Pacific zooxanthellate corals (scleractinians and hydrocorals in the genus Millepora) number 41 species with about 10 species
occupying any particular site where they contribute more or less significantly toward reef building. Branching coral colonies in the genus Pocillopora, specifically Pocillopora damicornis (Linnaeus) and Pocillopora elegans Dana, are preeminent in reef building, forming intermeshing
compact frameworks not uncommonly attaining 2-3m in relief. Species
with massive, dome-shaped colony morphologies, such as Porites lobata
Dana, Pavona clavus Dana and Pavona gigantea Verrill, can also sometimes build mono- to paucispecific reef frameworks or contribute to pocilloporid reef building. Remarkably, these examples demonstrate that only
one or a few coral species are capable of building coral reefs.
Marginal coral framework development has been reported at Cabo
Pulmo-Los Frailes off SE Baja California (Fig. 19.1, site 1), and some of the
coral communities in this area accommodate a diverse alcyonarian fauna.
Fringing coral reefs occur in the Nayarit area and coral communities are
present at Bahia Banderas, which experiences local upwelling (Fig. 19.1,
site 2; Fig. 19.2A; Reyes Bonilla 1993; Carriquiry and Reyes Bonilla 1997).
Upwelling here is intensified topographically by a submarine canyon that
approaches close to the coast. Possibly one of the largest coral reefs in the