HR: 0800h
AN: V51C-1510    [Abstracts]
TI: Mariana Forearc Serpentine Mud Volcanoes Harbor Novel Communities of Extremophilic Archaea
AU: * Curtis, A C
EM: curtisa@cc.wwu.edu
AF: Western Washington University, Biology Department MS9160, Bellingham, WA 98225 United States
AU: Moyer, C L
EM: cmoyer@hydro.biol.wwu.edu
AF: Western Washington University, Biology Department MS9160, Bellingham, WA 98225 United States
AB: Since the Eocene (45 Ma) the Pacific Plate has been subducting beneath the Philippine Plate in the western Pacific ocean. This process has given rise to the Mariana Islands. As a direct result of this non-accretionary subduction, the Mariana Island Arc contains a broad forearc zone of serpentinite mud volcanoes located between the island chain and the trench. Forearc faulting, due to high pressure and low temperature build-up, produce slurries of mud and rock that mix with slab derived fluids and rise in conduits. Due to dehydration of the overlying mantle, native rock is converted to serpentinite, which squeezes out at fractures along the sea floor. This results in giant mud volcanoes (~30 km diameter and ~2 km high) that form a chain between 50 and 150 km behind the trench axis. Microbial samples were collected using Jason II from seven mud volcanoes along the length of the forearc and community fingerprinting was applied to genomic DNA using terminal restriction length polymorphism (T-RFLP). The resulting data were compared with traditional clone library and sequence analysis from samples obtained from the southernmost mud volcano, South Chamorro, site 1200, holes D and E, sampled during ODP Leg 195. The dominant archaeal phylotypes found clustered into two groups within the Methanobacteria, a class of anaerobic methanogens and methylotrophs. These phylotypes were detected at three of the seven mud volcanoes sampled and comprised 61% of the archaeal clone library from 1200 E. The first group was most closely related to the order Methanobacteriales, however, these novel phylotypes had similarity values of up to 0.90 at best with some resulting at 0.48. The second novel group of phylotypes were most closely related to order Methanosarcinales, with similarity values in the range of 0.50 to 0.22, indicating a relatively weak association with known phylotypes. At 1200 D, phylotypes associated with non-thermophilic Marine Group I Crenarchaeota were detected exclusively. These were also detected among all seven mud volcanoes and were found to comprise 39% of the library at 1200 E, potentially indicating near surface seawater mixing within some of the mud volcano sites. Phospholipid fatty acid (PLFA) content analyzed from 1200 E samples at 1.4 mbsf and 13.4 mbsf yield an increase of archaeal to bacterial biomass by 1000 and 500 times, respectively. These data, in conjunction with clone sequencing and fingerprinting information, points towards a novel archaeal subsurface community occurring within at least three of the seven Mariana forearc sites sampled. Additional sampling will be necessary to resolve the spatial variability detected.
UR: http://fire.biol.wwu.edu/cmoyer/research.html
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0463 Microbe/mineral interactions
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005