Description
- Abstract:
- Prokaryotic microbes, commonly termed bacteria, are essential components of the ecosystem in the open ocean. They are major primary producers, major diazotrophs that fix dinitrogen (N2) into new bio-available nitrogen, and are major consumers of dissolved organic matter (DOM). An ocean ecosystem model was constructed for the open ocean focusing on bacterial dynamics. A data assimilation technology was adapted to integrate the model with observations by objectively optimizing model parameters and minimizing the differences between the model results and observations. As up to 17 types of major biogeochemical observations, usually in seasonal or monthly profiles, were assimilated, the model was constrained and tested rigorously to fit different aspects of the ecosystem simultaneously. The 1-dimensional model was applied to three open ocean sites: the Arabian Sea, Equatorial Pacific and Hawaii Ocean Time-series (HOT). Good fitness to most of the observations supported the robustness of the model and reliability of the results. The results indicated the importance of heterotrophic bacteria in carbon cycling and nutrient regeneration in all the three sites. Semilabile DOM was identified as a stabilizing resource for heterotrophic bacteria. The model also indicated refractory DOM could be an important form of export from the upper ocean. Heterotrophic bacterial production (BP) observations improved the model by strengthening constraints on the model parameters. Despite uncertainties related to estimating BP, the model supported current estimates of BP as 5 ? 25% of primary production and the commonly-used conversion factors for BP measurements as 0.7 ? 3.1 kg C/mol leucine incorporation. A 15-year modeling experiment at HOT successfully simulated the observed interannual increase of primary production. The model suggested three mechanisms for this increase: (1) the deepening mixed layer and increased physical nitrate supply from the deep ocean, (2) enhanced nitrogen recycling as part of N2 fixation was replaced with physical nitrate supply, and (3) new nitrogen supply from semilabile DOM. The last two mechanisms only applied to the surface 20 m.
- Notes:
- Thesis (Ph.D.) -- Brown University (2010)
Access Conditions
- Rights
- In Copyright
- Restrictions on Use
- Collection is open for research.
Citation
Luo, Yawei,
"A Data Assimilating Model of the Microbial Ecosystem in the Open Ocean"
(2009).
Ecological and Evolutionary Biology Theses and Dissertations, Biology and Medicine Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z07W69GG
Relations
Collections:
-
Ecological and Evolutionary Biology Theses and Dissertations
Theses and Dissertations for the Ecological and Evolutionary Biology department.... -
Biology and Medicine Theses and Dissertations
Theses and Dissertations for the Biology and Medicine department....