Bacterial productivity of samples from three stations in the Western North Atlantic aboard R/V Atlantic Explorer cruise AE2413 during May 2024

Heterotrophic bacteria and archaea (here: microbes) are critical drivers of the ocean’s biogeochemical cycles, active throughout the depth of the ocean. Their capabilities and limitations help determine the rates and locations at which carbon and nutrients are regenerated, as well as the extent to which organic matter is preserved (Hedges 1992). In the deep ocean, at bathy- and abyssopelagic depths (ca. 1000-6000m), these communities are dependent upon the sinking flux of particulate organic matter (POM) from the surface ocean (Bergauer et al. 2018). This dependence means that heterotrophic microbial communities must produce the extracellular enzymes required to solubilize and hydrolyze high molecular weight (HMW) POM to sizes substrates suitable for cellular uptake. A recent global-scale investigation of deep-sea microbes in fact found that the genetic potential for exported (extracellular) enzymes among bacteria in deep waters was far greater than for communities in surface or mesopelagic waters (Zhao et al. 2020). We have new evidence that a substantial fraction of bacteria in bottom water from the North Atlantic Ocean use a specialized set of extracellular enzymes to rapidly take up HMW polysaccharides (Giljan et al. 2022), a substrate processing mechanism that would not be detected with the low molecular weight substrates used in most prior studies of microbial activity in the deep ocean (Nagata et al. 2010).

Through our collaboration with the Danish Center for Hadal Research, we were able to use pressurization systems and in situ specialized equipment to investigate the effects of pressures characteristic of bathy- and abyssopelagic depths on microbial communities and their extracellular enzymes in the open North Atlantic Ocean.   

Here we present the measurement of 3H-leucine incorporation by heterotrophic bacteria using a cold trichloroacetic acid (TCA) and microcentrifuge extraction method (Kirchman, 2001) at different sites in the Western North Atlantic aboard R/V Atlantic Explorer during during the research cruise AE2413 (2024-05-09 to 2024-05-28).  All work and incubations were performed in a UNOLS isotope lab, or within designated areas at the University of North Carolina at Chapel HIll post cruise. This dataset contains collection metadata, environmental conditions, sample types and treatments, incubation conditions, substrate types, radioactivity measurements, and calculated incorporation rates of 3H-leucine.