N-222. Archaea and mcrA Genes in the Water Column above Gas Hydrates and Cold Seeps in the Gulf of Mexico

B. Liu1, F. Wang2, G. Ye2, L. Wu3, F. Zhou1, Z. Huang1, J. Zhou3, J. Noakes1, C. L. Zhang1;
1Univ. of Georgia, Athens, GA, 2The Third Inst. of Oceanography, Xiamen, CHINA, 3Univ. of Oklahoma, Norman, OK.

Microorganisms play fundamental roles in the ecosystem of the Gulf of Mexico; yet their vertical distribution and functional variability in the water column are not well known. In this study, water column microorganisms were collected in the Mississippi Canyon (MC) block 118 (water depth 890 m) and Grand Canyon (GC) block 234 (water depth 530 m). The community structure of archaea was determined at discrete water depths using clone library and microarray approaches. Analysis of the 16S rRNA genes indicates that the Marine Group I of crenarchaeota are most frequently detected near the water bottom (800 m) at MC118 and in the mesopelagic water (140 m) at GC234; however, the Marine Group II of euryarchaeota are more frequently detected in the upper surface water (10 m) at MC118 and near the water bottom (500 m) at GC234. Clone libraries and microarray analyses show that mcrA genes are most frequently detected in the mesopelagic waters at MC118 (400 m) and GC234 (140 m). Compared to stratified microbial assemblages observed in other places of the open ocean, results in this study do not indicate a stratified distribution of the archaeal populations in the Gulf of Mexico. The presence of diverse mcrA genes in the aerobic water column of the Gulf of Mexico is intriguing and may be related to the dynamics of gas hydrates and cold seeps in the sediments below.