Table of Contents

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

Water was collected via Niskin bottles mounted on a rosette, equipped with a CTD in the Western North Atlantic aboard R/V Atlantic Explorer, cruise AE2413 in May 2024. Sampling was done at the following locations:

• stn24: 34.99333, -73.03333
• stn25: 34.99685, -68.24842
• stn26: 42.17828, -60.0479

At each station, seawater was transferred to 20 L carboys that were rinsed three times with water from the sampling depth and then filled with seawater from a single Niskin bottle, using silicone tubing that had been acid washed then rinsed with distilled water prior to use. From each carboy, water was dispensed into smaller glass containers that were cleaned and pre-rinsed three times with water from the carboy prior to dispensing. This water was used to measure cell counts,  and the activities of polysaccharide hydrolases  under varying hydrostatic pressures (0.1, 20, and 40 MPa).  A separate glass Duran bottle was filled with seawater from the carboy and sterilized in an autoclave for over 30 minutes to serve as a killed control for various measurements.

For each substrate and time point, three 3 mL Exetainer vials were filled with seawater and one 3 mL Exetainer vial was filled with autoclaved seawater to serve as a killed control. 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). Two 3 mL Exetainer vials – one with seawater and one with autoclaved seawater – with no added substrate served as blank controls. Vials for each substrate were pressurized to either 0.1, 20, or 40 MPa in individual pressure vessels for each time point and stored in the dark at 4ºC for 0, 5, 12, or 22 days.

At each time point, three pressure vessels were depressurized (one at 0.1, 20, and 40 MPa), vials were removed and using a sterile syringe, incubations were filtered through a 0.2 μm pore size syringe filter, and stored frozen until analysis.

Hydrolysis rates were calculated from the change in molecular weight distribution of the substrate over time, as described in detail in Arnosti (2003). 

Hydrolysis rates were calculated from the change in molecular weight distribution of the substrate over time, as described in detail in Arnosti (2003). Scripts to calculate hydrolysis rates are available in the associated Github repository (Hoarfrost, 2017).

- Imported "20250505_BCODMO_AE2413_FlaPS-bulk.csv" into BCO-DMO system
-Convert date to ISO YYYY-MM-DD date format
-Create ISO datetime, using "date" and "time"
-Renamed fields to remove spaces and special characters in keeping with BCO-DMO system and style guidelines
-Exported file as "968956_v1_ae2413_flaps_bulk.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.