Journal
NATURE GEOSCIENCE
Volume 9, Issue 12, Pages 888-+Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/NGEO2830
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Funding
- Friends of Long Marine Lab Student Research Awards
- UC Santa Cruz STEPS Institute for Innovation in Environmental Research
- UC Santa Cruz Center for the Dynamics and Evolution of the Land Sea Interface
- Earl H. Myers and Ethel M. Myers Oceanographic and Marine Biology Trust
- DC Santa Cruz Institute of Geophysics and Planetary Physics
- NSF [OCE-1358041, OCR-0623622, ARC-1022716]
- US Department of Energy [W-7405-Eng-48, DE-AC52-07NA27344]
- Keck Carbon Cycle AMS Laboratory Postdoctoral Scholarship
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Marine organic matter is one of Earth's largest actively cycling reservoirs of organic carbon and nitrogen(1,2). The processes controlling organic matter production and removal are important for carbon and nitrogen biogeochemical cycles, which regulate climate. However, the many possible cycling mechanisms have hindered our ability to quantify marine organic matter transformation, degradation and turnover rates(3,4). Here we analyse existing and new measurements of the carbon: nitrogen ratio and radiocarbon age of organic matter spanning sizes from large particulate organic matter to small dissolved organic molecules. We find that organic matter size is negatively correlated with radiocarbon age and carbon: nitrogen ratios in coastal, surface and deep waters of the Pacific Ocean. Our measurements suggest that organic matter is increasingly chemically degraded as it decreases in size, and that small particles and molecules persist in the ocean longer than their larger counterparts. Based on these correlations, we estimate the production rates of small, biologically recalcitrant dissolved organic matter molecules at 0.11-0.14 Gt of carbon and about 0.005 Gt of nitrogen per year in the deep ocean. Our results suggest that the preferential remineralization of large over small particles and molecules is a key process governing organic matter cycling and deep ocean carbon storage.
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