Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Water for incubation and filtration was collected via Niskin bottles mounted on a rosette, equipped with a CTD for Western North Atlantic, Danish Coastal Seawater, and Abyssopelagic Waters off the Eastern Coast of Japan. Additionally, in the Western North Atlantic, water was collected via an in-situ syringe-based sampler and incubator developed by the Danish Center for Hadal Research.  

Niskin-collected water was used to measure cell counts and investigate selfish polysaccharide uptake under near-surface (0.1 MPa), or bathy- and abyssopelagic hydrostatic pressures (20, 40, 42 and 52 MPa). Water at each station was dispensed into smaller glass Duran bottles that were cleaned and pre-rinsed three times with water from the Niskin prior to dispensing. To 350 mL of bulk seawater or 100 mL of autoclaved seawater, substrate was added at 3.5 μM monomer-equivalent concentrations, except for fucoidan, which was added at 5 μM concentrations (a higher concentration was necessary for sufficient fluorescence signal). From these bottles, nine 6 mL Exetainer vials were filled with seawater for each substrate, replicate, and time point, and four 6 mL Exetainer vials were filled with autoclaved seawater to serve as a killed control. Sets of vials were then pressurized to either 0.1, 20, or 40 MPa in separate pressure vessels for each substrate and time point and stored in the dark at 4ºC for 0, 2, or 5 days.

When collected via an in-situ syringe sampler (ISS), glass syringes fitted to the sampler were preloaded with individual polysaccharide substrates to 3.5 μM monomer-equivalent concentrations or preloaded with autoclaved seawater to serve as a negative control (blank).  Once lowered to the desired depth of 2000, 4000, 4200, or 5200 m (depending on station depth), half of the syringes were triggered so that they drew in surrounding water that mixed with the preloaded substrate or autoclaved seawater.  The ISS was held at depth for approximately 24 hours of incubation.  While still at depth, shortly prior to retrieval, the second half of the syringes were triggered to draw in the surrounding water. These syringes served to measure the quantity of selfish uptake occurring briefly at depth, and then during the upcast. 

After sample incubation, approximately 25 mL of incubated sample was filtered through a 25 mm 0.2 µM nucleopore filter for molecular analysis, placed in cryovials, and promptly frozen at -80C.

Another approximately 25 mL of incubated sample was incubated with fixative for two hours, then filtered through a 25 mm 0.2 µM nucleopore filter.  After filtration, the filters were dried in a laboratory hood, then each filter was labeled along the outer edge, placed in a Petri dish, and stored at -80C for total cell counts, and quantification of 'selfish' uptake.

Polysaccharide used for incubation:

• ara = arabinogalactan
• chn = chondroitin sulfate
• fuc = fucoidan
• lam = laminarin
• man = mannan
• pul = pullulan
• xyl = xylan
• muc = mucin

Image analysis was performed with ACMETOOL (http://www.technobiology.ch and Max Planck Institute for marine microbiology, Bremen, version 3) and Zen software package (Carl Zeiss). 

- Imported "20250410_BCODMO_Detection and Quantification of Cells Exhibiting 'Selfish' Uptake combined data_csv.csv" into the BCO-DMO system
- Normalized the capital letters in the "Surface" value for the "depth" parameter
- Replaced all cruise names starting with "Helsingor - Sept" to "Helsingor - Sept 2023", so they are all the same and reflect the cruise name given in the parameter descriptions
- Replaced ø → o for system requirements
- Converted date to YYYY-MM-DD
- Created ISO formatted datetime field in UTC
- Reversed the lat and lon for "AE2413", as they were reversed
- Renamed fields for clarity, consistency, and to comply with BCO-DMO naming requirements
- Exported file as "963393_v1_selfish_bacteria_cell_counts.csv"

NSF Award Abstract:
Microbes are important players in the carbon cycle in the ocean. These organisms consume organic carbon and produce carbon dioxide in marine systems. Because the average depth of the ocean is 4000 m, microbes must work at high pressures typical of the deep ocean (>1000 m). Although high pressure is known to affect marine microbes, their carbon cycling activities have mostly been measured at surface ocean pressures. As a result, it remains unknown how closely these measurements reflect the activities of deep-sea microbes at high pressures. As a result of collaborations with scientists in Denmark and Germany, this project will be able to use special equipment to investigate the effects of high pressures on marine microbes and their carbon cycling activities. This work is necessary to quantify rates of carbon cycling and identify the microbes involved, especially in deep waters. The project will provide training for diverse undergraduate and graduate students, and a postdoc who will conduct novel research in the U.S., Denmark, and Germany, both at sea and in the lab. The scientists will also teach middle school students about the role of microbes in the carbon cycle and pressure effects on life in the ocean. The project will provide internships for high school students, focusing on first-generation students who would like to go to college. This work may aid in future efforts to identify enzymes that function well under high pressure.

Heterotrophic microbes (e.g., bacteria and archaea) are found throughout the ocean. Their biogeochemical functions help determine the rates and locations at which carbon and nutrients are regenerated, as well as the extent to which organic matter is preserved. Although research has shown that pressure profoundly affects the activities of marine microbes, most investigations of microbial communities of the deep sea are conducted at atmospheric pressure, due to the limited availability of specialized equipment. In collaboration with the Danish Center for Hadal Research at the University of Southern Denmark, this study will identify the effects of pressure on microbial communities and their extracellular enzymes of pressures characteristic of bathy- and abyssopelagic depths. At sea and in the lab, the scientific team will compare the effects of depressurization on the activities of enzymes produced by microbial communities of the deep ocean, as well as the effects of high pressure on surface-water derived enzymes and communities. Fieldwork will take place in Danish coastal waters, well as in the open North Atlantic and Pacific Oceans. Using pressurization systems and in situ incubations, this study will measure hydrolysis rates of peptides and polysaccharides, two of the major classes of marine organic matter. Project activities will also focus on developing the means to measure enzyme activities in situ in the deep ocean. In collaboration with colleagues from the Max Planck Institute for Marine Microbiology in Germany, this proect will additionally investigate whether pressure affects the selfish uptake of polysaccharides. These studies will provide new insight into understudied but key factors that help determine the fate of organic matter in the deep ocean.

This project is funded by the Biological and Chemical Oceanography Programs.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.