and west. The basin is very flat, having a gradient of only about 0.3 m per
2,440 m. The deepest point in the Mexico Basin (Sigsbee Deep), is 5,203 m.
The Terminos Lagoon, the largest lagoon-estuarine ecosystem in Mexico, is
located in the southern GM. Terminos Lagoon is a large (*2,500 km
2 ), shallow
(mean depth 3.5 m) coastal lagoon bordering the southern Gulf of Mexico in
Campeche, with 200,108 ha of open water including associated lagoons and
channels, surrounded by about 259,000 ha of mangroves and cattail marshes. The
lagoon borders two geological provinces: to the east the Yucatan Peninsula (low
rainfall, calcareous soils, and no significant surface drainage); to the west and
south, the lowlands of Tabasco and the highlands of Chiapas and Guatemala.
Offshore is the Bay of Campeche, a region supporting one of the largest marine
fisheries in Mexico. The Usumacinta-Grijalva river systems discharge into the
Gulf by three main rivers: the Candelaria, the Chumpan, and the Palizada. The
lagoon is surrounded by shores and is fully incorporated into a National Flora and
Fauna Reserve that comprises 705,016 ha of open water and associated wetlands
and upland (Yañez-Arancibia et al. 1983) (Fig. 2.1).
The Mexican Caribbean and the Yucatan Peninsula is a northeastern projection
of Central America, lying between the GM to the west and north and the Caribbean
Sea to the east, encompassing some 197,600 km
2 . It includes the Mexican states of
Campeche, Quintana Roo, and Yucatan and, to the south, large parts of Belize and
Guatemala. The peninsula has a mean width of about 320 km and a coastline of
about 1,100 km (De la Lanza-Espino 1991). The Yucatan Peninsula subsurface
Caribbean water (16–20 °C, 36.1–36.5 %) upwells along the eastern slope of the
Yucatan shelf. This water, which originates at depths of about 220–250 m in the
Yucatan Channel, rises at about 10 cm s
-1 into the euphotic zone and only
occasionally breaks the ocean surface. This upwelling follows a seasonal cycle.
During spring and summer the upwelled water intrudes over the Yucatan shelf to
create a two-layered water column. Yucatan is one of the most important
upwelling regions on a western oceanic margin (Merino 1997) (Fig. 2.1).
2.2 Echinoderm Fauna of Mexico: An Inventory and Analysis
2.2.1 Historical Review
Studies on Mexican echinoderms started in the nineteenth century, when some
specimens were collected and analyzed by Louis Agassiz in 1841. He reported the
presence of the sand dollar Mellita quinquiesperforata (as Mellita hexapora) in the
Gulf of Mexico (Veracruz). Later, Verrill (1870, 1871) published on some specimens collected by Yale University in Mexican waters. The Blake expeditions to
the Gulf of Mexico and Caribbean (1878 and 1884) produced several papers, such
as Perrier (1881) on Asteroidea, Lyman (1883) on Ophiuroidea, Théel (1886) on
Holothuroidea and Agassiz (1878–1879, 1888) on Echinodea. The Challenger
14
F. A. Solís-Marín et al.
2,440 m. The deepest point in the Mexico Basin (Sigsbee Deep), is 5,203 m.
The Terminos Lagoon, the largest lagoon-estuarine ecosystem in Mexico, is
located in the southern GM. Terminos Lagoon is a large (*2,500 km
2 ), shallow
(mean depth 3.5 m) coastal lagoon bordering the southern Gulf of Mexico in
Campeche, with 200,108 ha of open water including associated lagoons and
channels, surrounded by about 259,000 ha of mangroves and cattail marshes. The
lagoon borders two geological provinces: to the east the Yucatan Peninsula (low
rainfall, calcareous soils, and no significant surface drainage); to the west and
south, the lowlands of Tabasco and the highlands of Chiapas and Guatemala.
Offshore is the Bay of Campeche, a region supporting one of the largest marine
fisheries in Mexico. The Usumacinta-Grijalva river systems discharge into the
Gulf by three main rivers: the Candelaria, the Chumpan, and the Palizada. The
lagoon is surrounded by shores and is fully incorporated into a National Flora and
Fauna Reserve that comprises 705,016 ha of open water and associated wetlands
and upland (Yañez-Arancibia et al. 1983) (Fig. 2.1).
The Mexican Caribbean and the Yucatan Peninsula is a northeastern projection
of Central America, lying between the GM to the west and north and the Caribbean
Sea to the east, encompassing some 197,600 km
2 . It includes the Mexican states of
Campeche, Quintana Roo, and Yucatan and, to the south, large parts of Belize and
Guatemala. The peninsula has a mean width of about 320 km and a coastline of
about 1,100 km (De la Lanza-Espino 1991). The Yucatan Peninsula subsurface
Caribbean water (16–20 °C, 36.1–36.5 %) upwells along the eastern slope of the
Yucatan shelf. This water, which originates at depths of about 220–250 m in the
Yucatan Channel, rises at about 10 cm s
-1 into the euphotic zone and only
occasionally breaks the ocean surface. This upwelling follows a seasonal cycle.
During spring and summer the upwelled water intrudes over the Yucatan shelf to
create a two-layered water column. Yucatan is one of the most important
upwelling regions on a western oceanic margin (Merino 1997) (Fig. 2.1).
2.2 Echinoderm Fauna of Mexico: An Inventory and Analysis
2.2.1 Historical Review
Studies on Mexican echinoderms started in the nineteenth century, when some
specimens were collected and analyzed by Louis Agassiz in 1841. He reported the
presence of the sand dollar Mellita quinquiesperforata (as Mellita hexapora) in the
Gulf of Mexico (Veracruz). Later, Verrill (1870, 1871) published on some specimens collected by Yale University in Mexican waters. The Blake expeditions to
the Gulf of Mexico and Caribbean (1878 and 1884) produced several papers, such
as Perrier (1881) on Asteroidea, Lyman (1883) on Ophiuroidea, Théel (1886) on
Holothuroidea and Agassiz (1878–1879, 1888) on Echinodea. The Challenger
14
F. A. Solís-Marín et al.