12 Guaymas Basin and Gulf of California Subsurface Systems and Energy Applications

This session will present subsurface research in the Gulf of California, especially IODP Expedition 385 to Guaymas Basin that explored the linkages between tectonics, magmatism, sedimentation, hydrothermalism, carbon cycling, and microbial life. Merged sessions: Subsurface Research  in Guaymas Basin and the Gulf of California and Energy Resources and Economic Development in Baja California: Fossil, Renewable, and Transition Minerals.

Wednesday, 22 April 2026
1:30 PM - 5:30 PM
LMH, Isla Carmen

The Guaymas Basin Subsurface Biosphere (IODP 385): Current Updates on Genome-based Studies

Paper number: 12-5
Program: Technical Sessions
Time: 2:35 PM – 2:50 PM

Authors

Abstract

Deep subsurface sediment and sill rock samples collected during IODP expedition 385 across Guaymas Basin (Sites U1545-U1552) provide an opportunity to explore changing microbial diversity and metabolic functions within steep temperature and geochemical gradients. Using a combination of metagenomic and primer-dependent gene sequencing, we are working out general patterns of microbial community structure in the Guaymas Basin subsurface. MAG-based metagenomic recruitment shows a distinct pattern: While temperate sediments (3-20°C) are dominated by cosmopolitan lineages of heterotrophic, anaerobic bacteria and archaea, this community is losing ground in warm sediments (20-45°C) and has practically disappeared in hot sediments (>45°C). Uncultured Bathyarchaeota and Hadarchaeota persist until ca. 60°C in-situ temperature in subsurface sediments, and were also detected in a veined sill sample at ca. 80°C, suggesting connectivity between microbial communities of deep sediment and sills (analogous to recent observations from Juan de Fuca sediments and basalt).

So far, all genome and sequence-based studies of the Guaymas deep biosphere are limited by marginal DNA recovery from deep sediments and elevated temperatures above approximately 40°C; the genomic window into the deep biosphere gradually closes at higher temperatures. Therefore, deep and/or thermophilic microbial communities could be missed due to low population densities and DNA yield. Interestingly, traces of hydrothermal vent archaea appear predominantly at Ringvent (U1547 and U1548), mostly at moderate depths and temperatures as potential residues of hydrothermal circulation. Concerning microbial cycling of methane, the most abundant carbon source in Guaymas basin, methane-oxidizing archaea (ANME) are widespread, although in low sequence abundance, but they are found more consistently at cold seep-influenced sites. The preferential detection of ANME-1 key genes (order Methanophagales) over classical methanogens suggests a microbial community more attuned to methane oxidation than methanogenesis. Last but not least, a focused search for cell defense genes in bacterial and archaeal MAGs of the Ringvent sites (U1547 and U1548) was highly successful across a wide depth and temperature range; it uncovered an extensive repertoire of genome-encoded defense systems in the deep biosphere, which likely regulates survival-relevant gene expression and metabolic energy expenditures while countering viral attacks.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410756

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