[EN683 Bacterial Productivity] - Bacterial Productivity measurement of bulk seawater and mesocosm experiments taken aboard the R/V Endeavor in the Western North Atlantic during the research cruise EN683 in May and June, 2022 (Substrate structural complexity and abundance control distinct mechanisms of microbially-driven carbon cycling in the ocean)

Samples were collected at different sites in the Western North Atlantic and from mesocosm experiments using seawater from those sites. All work and incubations were performed in a UNOLS isotope lab aboard R/V Endeavor during the research cruise EN683 (2022-05-24 to 2022-06-12), or within designated areas at the University of North Carolina at Chapel Hill post cruise.

This research tested the hypothesis that the mechanism of polysaccharide processing is related to the cost to a cell of producing the enzymes required for its hydrolysis, and the probability that a cell will receive sufficient return on investment for producing the enzymes. Our conceptual model suggests that external (extracellular) hydrolysis is favored when organic matter is abundant, or when enzyme production costs can be shared (e.g., on particles, in biofilms); selfish uptake (hydrolysis without production of low molecular weight products in the environment) would be a better strategy when high molecular weight (HMW) organic matter is scarce, and particularly when the HMW organic matter is very complex.