329: South Pacific Gyre Subseafloor Life

Map of locations for sites that were drilled during Leg 329 on the South Pacific Gyre off of the coast of New Zealand. Figure from IODP Expedition 329 Summary.

International Ocean Drilling Program (IODP) Expedition 329 took place from October to December in 2010 and drilled Sites U1365–U1371 in the South Pacific Gyre, a large system of rotating ocean currents in the South Pacific Ocean located off the coast of New Zealand. The expedition was a collaboration between scientists and staff from the United States, Japan, Germany, China, Norway, the United Kingdom, New Zealand, Korea, Australia, and India. Currently, there are no other ocean drilling sites located near Expedition 329 sites making it a massively understudied location. The sites drilled and studied during this expedition are an excellent location for exploring and researching subseafloor sedimentary habitats in what is considered to be the center of an open ocean gyre. The South Pacific Gyre is Earth’s largest gyre system out of five total gyre systems. Even though the cores recovered on Expedition 329 vary in ages, they are all extremely useful in understanding hydrothermal circulation (the circulation of hot water), and habitability (the capacity to be lived in) of oceanic crusts. 

Detailed image of a calcite crystal contained within a section of basalt, the rock that makes up the ocean crust. Blue coloring is from a marker. Image from the LIMS Database.

Expedition 329 had four major objectives: 1) to document habitats; 2) research how oceanographic factors affect habitats; 3) quantify subseafloor microbial communities; and 4) determine how habitats at the sites vary with crust age. Before Expedition 329, life in the sediments beneath mid-ocean gyres was generally understudied and poorly understood, despite the South Pacific Gyre being a unique location. Within this gyre system, surface chlorophyll concentrations and primary photosynthetic productivity in the seawater are lower than in other ocean regions, contributing to some of the lowest organic burial rates in the ocean. Scientists and staff aboard the ship during this expedition found that microbial cell counts are lower than at all sites previously drilled, dissolved oxygen and nitrate are present throughout the entire sediment sequence, and dissolved hydrogen concentration is low but often above detection limits in deeper sediments. High-resolution chemical and physical measurements provided the opportunity for reconstructing glacial seawater characteristics through the South Pacific Gyre. Overall, Expedition 329’s findings and discoveries of the presence of dissolved chemicals revealed that there is microbial habitability of the entire sediment sequence, offering valuable insights into gyre habitability.


D’Hondt, S.L., Jørgensen, B.B., Miller, D.J., et al., 2003. Proc. ODP, Init. Repts., 201: College Station, TX (Ocean Drilling Program). doi:10.2973/odp.proc.ir.201.2003

Dubois, N., Mitchell, N. C., & Hall, I. R. (2014, April). Data report: particle size distribution for IODP Expedition 329 sites in the South Pacific Gyre. In Proc. IODP| Volume (Vol. 329, p. 2).

Expedition 329 Scientists, 2011. Methods. In D’Hondt, S., Inagaki, F., Alvarez Zarikian, C.A., and the Expedition 329 Scientists, Proc. IODP, 329: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.329.102.2011

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