ORCID
0009-0008-9995-212X (Craft), 0000-0001-8281-3184 (Bochdansky)
Document Type
Article
Publication Date
2025
DOI
10.1002/lno.12796
Publication Title
Limnology and Oceanography
Volume
Article in Press
Pages
1-16
Abstract
The mesopelagic zone is a site of strong microbially driven particle attenuation with depth and thus plays a crucial role in controlling the transfer efficiency of the ocean's biological pump. However, little quantitative information exists on the dependency of decay processes on the source material. Here we followed the decay of ¹⁴C-labeled dead particulate organic carbon (POC) and dissolved organic carbon (DOC) from three different phytoplankton species, and two incubations of live diatoms, in mesopelagic water over 3 months. Commonly used first-order kinetics failed to adequately describe the decay of organic material as rate constants varied from day to day. Over extended periods, decay rates for organic material exhibited two distinct phases, with rates in the second phase being inversely related to rates in the first phase. Microbial biomass (measured via adenosine triphosphate and cell counts) increased substantially during phase 1 and ebbed during phase 2. Decay rates were significantly different among the three algal sources; however, differences were even more pronounced among carbon pools and followed a distinct pattern (combined average per-day decay rates at 12°C): fresh DOC (0.6) > fresh POC (0.1) > live cells (0.06) > aged DOC/POC (0.01). Separation of POC into four broad biochemical fractions showed that components in the operationally defined lipid fraction contained the most degradable compounds for fresh material. Our research highlights the need to include the dynamics of the most easily digestible fractions of freshly released organic material, and live plankton resilient to digestion, in calculations of vertical carbon flux budgets.
Rights
© 2025 The Authors.
This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Data Availability
Article states: "Data from this study are available at the Biological and Chemical Data Management Office (BCO-DMO) under the project number OCE-1851368 and the lead PI's name (Bochdansky)."
Original Publication Citation
Craft, N. J., & Bochdansky, A. B. (2025). Organic carbon decay mediated by a mesopelagic microbial community: The relevance of carbon pools and broad biochemical composition. Limnology and Oceanography. Advance online publication. https://doi.org/10.1002/lno.12796
Repository Citation
Craft, Noah J. and Bochdansky, Alexander B., "Organic Carbon Decay Mediated by a Mesopelagic Microbial Community: The Relevance of Carbon Pools and Broad Biochemical Composition" (2025). OES Faculty Publications. 534.
https://digitalcommons.odu.edu/oeas_fac_pubs/534
Supporting Information