Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset contains the sample log for HADESK bacterial biomarker phospholipid fatty acid (PLFA) content from sediment push cores. The same samples were also used for the organic matter (OM) analysis.  Samples were taken in the Kermadec Trench in the Southwest Pacific, 4000 to ~10,000m from the RV/ Thomas G. Thompson during cruise TN309, May 2014.

Push cores (6.35 cm diameter) of sediment were collected in situ using the manipulator arm of the Hybrid Remotely Operated Vehicle Nereus on the margin of the Kermadec Trench (6013m) and along the main trench axis (7137 to 9177m) at roughly 1000m increments.

Cores were sectioned at 1cm intervals and sieved for the meiofaunal fraction.

Upon retrieval of sediment cores, the 0-1, 1-2, 2-3, 3-5, 5-10 cm depth horizons were sectioned and stored frozen (-80 °C) until analysis. Benthic bacterial biomass were calculated from sediment concentrations of the bacterial biomarker phospholipid fatty acids (PLFAs) i14:0, i15:0, ai15:0, i16:0. In brief, PLFAs were extracted and purified from known quantities of freeze-dried sediment samples and subsequently derivatized to yield fatty acid methyl esters (FAMEs). FAMEs were quantified using GC-FID (Agilent Technologies 6890N). Bacterial biomass was calculated using the well-established PLFA:C conversion factor of 0.056 gC PLFA/gC biomass.

Attempts were made to obtain 3 replicate cores at each depth horizon (every 1000 meters from 6000m to 10,000m.  For logistical reasons with vehicle performance (and loss at 10,000), all of the replicates were not able to be collected.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- re-formatted date from m/d/yyyy to yyyy-mm-dd

Extracted from the NSF award abstract:

Severe technical challenges associated with the extremes of hydrostatic pressure have prevented major advances in hadal ecological studies, and relegated hadal systems to among the most poorly investigated habitats on Earth. Through this project, Hadal Ecosystems Studies (HADES) program, PIs will determine the composition and distribution of hadal species, the role of hadal pressures (piezolyte concentrations, enzyme function under pressure), food supply (distribution of POC with the abundance and biomass of trench organisms, and metabolic rates/energetic demand), and depth/topography (genetic divergence and spatial connectivity of populations) have on impacting deep-ocean community structure. This project will examine these factors using the world's first full-ocean depth hybrid remotely operated vehicle (HROV) in conjunction with the only full-ocean depth imaging lander (Hadal-Lander). This project will provide the first seafloor data and samples in one of the world's best, yet little known trenches- the Kermadec Trench (SW Pacific Ocean).  Megafaunal community structure and the relationship between POC and benthic bacterial biomass will be examined as a function of depth and location by systematic high-definition imaging and sediment/faunal sampling transects from abyssal to full trench depths both along and perpendicular to the trench axis. Population genetic approaches will provide levels of genetic divergence and evolutionarily independent lineages to assess the role of depth and topography in trenches and their adjacent abyssal plain in promoting the formation of species. Physiological constraints will be investigated by examining in-situ respiration of selected fauna and tissue concentrations of such protein stabilizers as trimethylamine oxide (TMAO), and the structural adaptations of macromolecules. 

Image of NEREUS Deployment Sites. [click on the image to view a larger version]