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Voyage to Atacama Trench, March 2 – April 4, 2018

This is the second major expedition in the HADES-ERC project. This time we will target the Atacama Trench in the East Pacific Ocean.
We will investigate both sites in the Atacama Trench system including the adjacent abyssal and bathyal sites off Chile. Depths of the target stations will range between 1000 – 8065 m. We aim for 5 hadal stations within the Atacama Trench, 3 depth transects with stations at ca. 6,000 m and 3,000 m and 3 stations at 1,000 m at the continental shelf off Chile.

The Atacama Trench is underlying one of the most productive oceans in the world and therefore it represents an extreme end-member for hadal environment with high deposition of organic material.

We suspect this will have important implication for the biological and biogeochemical function of the trench. It is already known that the sediment has high densities of for instance meiofauna.

We want to compare conditions in trench and abyssal plain

We also expect that the trench sediment will host significant anaerobic degradation of organic material, which makes it a unique site for investigating processes of nitrogen cycling and sulfate reduction at extreme pressure – presumably mediated by completely unknown microbial communities.

We want to quantify the carbon mineralization efficiency in the eutrophic Atacama Trench and compare it to conditions in the neighboring abyssal plain.

The result will add to our growing database on microbial carbon mineralization in hadal settings and allow for comparison between hadal environments experiencing different regimes of organic carbon deposition.

Specific questions we would like to address during this cruise are:

  • What are the sedimentary processes sustaining the hadal community in the Atacama Trench?
  • How do abundance, diversity and community structure of microorganisms, meio- and macrofauna in the Atacama Trench differ from those in less productive trenches and nearby abyssal and shelf sites?
  • What are the general biogeochemical characteristics of the surface and deep sediment, bottom water and water column in the euthrophic Atacama Trench?
  • Which mineralization pathways are responsible for the organic matter break down in the eutrophic Atacama Trench?
  • How efficient are microbial communities operating at extreme hydrostatic pressures in mineralizing organic material as compared to their shallower counterparts? And to what extent do specialized unknown extremophile microbial communities mediate these processes?

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