Journal
FRONTIERS IN MARINE SCIENCE
Volume 4, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fmars.2017.00436
Keywords
temperature; dissolved organic carbon; mineralization; Arrhenius law; global ocean biogeochemical model
Funding
- Australian Institute of Marine Science
- Carlsberg Foundation
- FEDER funds
- U.S. DOE Office of Science [DE-SC0016329]
- US National Science Foundation [OCE-1436748]
- Spanish Ministry of Economy and Competitiveness [CSD2008-00077, CTM2011-30010-C02-02, CTM2015-69392-C3-2-R]
- Directorate For Geosciences
- Division Of Ocean Sciences [1436748] Funding Source: National Science Foundation
- U.S. Department of Energy (DOE) [DE-SC0016329] Funding Source: U.S. Department of Energy (DOE)
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More than 96% of organic carbon in the ocean is in the dissolved form, most of it with lifetimes of decades to millennia. Yet, we know very little about the temperature sensitivity of dissolved organic carbon (DOC) degradation in a warming ocean. Combining independent estimates from laboratory experiments, oceanographic cruises and a global ocean DOC cycling model, we assess the relationship between DOC decay constants and seawater temperatures. Our results show that the apparent activation energy of DOC decay (E-a) increases by three-fold from the labile (lifetime of days) and semi-labile (lifetime of months) to the semi-refractory (lifetime of decades) DOC pools, with only minor differences between the world's largest ocean basins. This translates into increasing temperature coefficients (Q(10)) from 1.7-1.8 to 4-8, showing that the generalized assumption of a constant Q(10) of similar to 2 for biological rates is not universally applicable for the microbial degradation of DOC in the ocean. Therefore, rising ocean temperatures will preferentially impact the microbial degradation of the more recalcitrant and larger of the three studied pools. Assuming a uniform 1 degrees C warming scenario throughout the ocean, our model predicts a global decrease of the DOC reservoir by 7 +/- 1 Pg C. This represents a 15% reduction of the semi-labile + semi-refractory DOC pools.
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