Dissolved Organic Matter
Conceptual definition
At approximately 662 gigatons of carbon (GtC), Dissolved Organic Matter (DOM) far outnumbers Particulate Organic Matter, which includes organisms and marine snow, and constitutes more than 99% of organic carbon in the ocean's water column[1]. Yet, most DOM released by phytoplankton, the primary source of DOM, is quickly degraded by heterotrophs within hours to days[2]. As a result, the majority of DOM (~630 GtC) that is found in the ocean has a lifetime (determined via 14C-carbon dating) of over 16,000 years[2].
DOM is operationally defined as organic carbon that flows through a GF/F glass fiber filter, with the retentate on the filter being defined as Particulate Organic Matter, and classified into the following groups based on their lifetime[2]:
- labile DOM (removal within hours to days)
- semi-labile DOM (removal within weeks to months)
- semi-refractory DOM (removal over years to decades)
- refractory DOM (removal over centuries to millenia)
Subfield notes
Experimental
On a molecular level, DOM comprises thousands or even millions of unique structures[2]. Most studies investigating the molecular composition of DOM resort to PPL-SPE, a moderately hydrophobic solid phase extraction technique designed to extract the largest possible amount of DOM from seawater while removing salts that can interfere with downstream analytical processes[3]. This fraction of DOM is called SPE-DOM (3).
Models
Models represent DOM as groups of organic carbon as listed above (labile, semi-labile, semi-refractory and refractory) with varying lifetime as only descriptor[4], sometimes adding an ultra-refractory group[5].
References
- ↑ Hansell, D.A., C.A. Carlson, D.J. Repeta, and R. Schlitzer. 2009. Dissolved organic matter in the ocean: A controversy stimulates new insights. Oceanography 22(4):202–211, https://doi.org/10.5670/oceanog.2009.109
- ↑ 2.0 2.1 2.2 2.3 Dittmar, T., Lennartz, S.T., Buck-Wiese, H. et al. Enigmatic persistence of dissolved organic matter in the ocean. Nat Rev Earth Environ 2, 570–583 (2021). https://doi.org/10.1038/s43017-021-00183-7
- ↑ Dittmar, T., Koch, B., Hertkorn, N., Kattner, G., (2008), A simple and efficient method for the solid-phase extraction of dissolved organic matter (SPE-DOM) from seawater, Limnol. Oceanogr. Methods, 6, https://doi:10.4319/lom.2008.6.230
- ↑ Kim, H. H. (2025). BATS-1D-VAR v1.0: A One-Dimensional Variational Data Assimilative Biogeochemical Model of the Bermuda Atlantic Time-Series Study (BATS) Site. Zenodo. https://doi.org/10.5281/zenodo.17148897
- ↑ Emily J. Zakem et al., Functional biogeography of marine microbial heterotrophs. Science388, eado5323 (2025). https://doi.org/10.1126/science.ado5323