GULF OF MEXICO HYDROCARBON SEEP ECOSYSTEM STUDIES 



James M. Brooks 1 Eric N. Powell 2 , Mahlon C. Kennicutt II 3 , 

 Robert S. Carney 2 , Ian R. MacDonald 2 , Susanne J. McDonald 1 , 

 Robert R. Bidigare 1 , and Terry L.Wade 1 



1 - Geochemical and Environmental Research Group 



Texas A&M University 



College Station, TX 77840 



2 - Department of Oceanography 



Texas A&M University 



College Station, TX 77840 



3 - Coastal Ecology Institute 



Louisiana State University 



Baton Rouge, LA 70803 



ABSTRACT 



The northern Gulf of Mexico continental slope is the 

 site of a number of unique discoveries in the last few 

 years. Active seepage of oil to the sea surface has been 

 observed in the Green Canyon-184/185 and 190/234 areas. In 

 at least one of these areas, extensive molecular and 

 isotopic analyses have demonstrated that the petroleum in 

 shallow sediments and surface oil slicks is derived from 

 reservoirs more than 2500 m deep in the subsurface. Ten 

 locations on the Lousiana slope (530 to 2400 m water depth) 

 have currently been identified that contain either biogenic 

 or thermogenic gas hydrates in shallow sediments ( <8 m). 

 Analyses of bitumens from several thousand cores from the 

 continental slope suggest that seepage is a widespread 

 phenomena on the Gulf of Mexico continental slope. This 

 seepage drives large populations of chemosynthetic 

 organisms. A number of new species of tube worms and 

 bivalves are being described from the trawl and submersible 

 collections at these sites. 



INTRODUCTION 



The northern Gulf of Mexico continental slope has been 

 the site of a number of recent discoveries that have 

 dramatically altered our understanding of chemical, 

 biological and geological processes on the continental 

 slope. The Geochemical and Environmental Research Group at 

 Texas A&M University reported the first occurrence of 

 thermogenic gas hydrates in oil-stained cores in deep ocean 

 sediments in 1984 (Brooks et al., 1984). Trawling in these 

 areas has identified tube worms and bivalves containing 



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