THE TEXAS-LOUISIANA CONTINENTAL SHELF ECOSYSTEM 



The Gulf of Mexico is an oval sea having an approximate surface 

 area of over 1.6 million km 2 and a maximum depth of about 3»840 m 

 (Figure 2) . Oceanic water enters the gulf from the Caribbean Sea 

 through the Yucatan Channel (<160 km wide and 1,650 to 1,900 m deep) and 

 exits through the Florida Channel (<160 km wide and about 800 m deep); 

 both openings are located in the southeastern sector of the gulf. This 

 feature, combined with the fact that runoff from some two- thirds of the 

 United States and more than half of Mexico empties in the northern and 

 western part of the basin, serves to divide the gulf into two major 

 provinces — a carbonate province to the east and a terrigenous one to the 

 west (Uchupi 1967). Based upon topography, Uchupi (1967) further 

 subdivided the gulf into additional major physiographic 

 provinces — namely the continental shelf, the continental slope, the 

 Mississippi Fan, the continental rise and the Sigsbee Abyssal Plain. 

 The shelf province is subdivided as the West Florida Shelf, the 

 Mississippi-Alabama Shelf, the Texas-Louisiana Shelf, the East Mexico 

 Shelf, and the Campeche Shelf (Figure 2) . 



Antoine (1972) divided the Gulf of Mexico into seven distinct 

 geological provinces. Of these, his Northern Gulf of Mexico Province 

 corresponds with the Texas-Louisiana Shelf and the Slope Provinces 

 presented by Uchupi (1967). Antoine (1972) described the Gulf of Mexico 

 basin as geologically old and representing a subsided oceanic area that 

 has been partially filled with sediments. 



The Texas-Louisiana continental shelf ecosystem has reasonably 

 distinct physical boundaries. It is bounded on the north and northwest 

 by land, on the east primarily by the Mississippi River birdfoot delta 

 which has bisected the shelf, and on the south and southwest by the 

 rapid change in slope which marks the transition from the continental 

 shelf to the continental slope ("118 m deep). The boundary to the 

 extreme south and southwest is less distinct, but is roughly placed at 

 the United States-Mexico border coinciding with the beginnings of the 

 anticlinal folds that generally parallel the shoreline in this area. 

 Some of the salient hydrographic processes and topographic features 

 considered important for assessment purposes are characterized in the 

 following section and are followed by descriptions of biological 

 systems. 



