Controls on the relative abundances and rates of nitrifying microorganisms in the ocean
<p>Nitrification controls the oxidation state of bioavailable nitrogen. Distinct clades of chemoautotrophic microorganisms – predominantly ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) – regulate the two steps of nitrification in the ocean, but explanations for their obs...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-12-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/19/5401/2022/bg-19-5401-2022.pdf |
| _version_ | 1811319938380464128 |
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| author | E. J. Zakem E. J. Zakem B. Bayer W. Qin A. E. Santoro Y. Zhang Y. Zhang N. M. Levine |
| author_facet | E. J. Zakem E. J. Zakem B. Bayer W. Qin A. E. Santoro Y. Zhang Y. Zhang N. M. Levine |
| author_sort | E. J. Zakem |
| collection | DOAJ |
| description | <p>Nitrification controls the oxidation state of bioavailable nitrogen. Distinct clades of chemoautotrophic microorganisms – predominantly ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) – regulate the two steps of nitrification in the ocean, but explanations for their observed relative abundances and nitrification rates remain incomplete and their contributions to the global marine carbon cycle via carbon fixation remain unresolved. Using a mechanistic microbial ecosystem model with nitrifying functional types, we derive simple expressions for the controls on AOA and NOB in the deep, oxygenated open ocean. The relative biomass yields, loss rates, and cell quotas of AOA and NOB control their relative abundances, though we do not need to invoke a difference in loss rates to explain the observed relative abundances. The supply of ammonium, not the traits of AOA or NOB, controls the relatively equal ammonia and nitrite oxidation rates at steady state. The relative yields of AOA and NOB alone set their relative bulk carbon fixation rates in the water column. The quantitative relationships are consistent with multiple in situ datasets. In a complex global ecosystem model, nitrification emerges dynamically across diverse ocean environments, and ammonia and nitrite oxidation and their associated carbon fixation rates are decoupled due to physical transport and complex ecological interactions in some environments. Nevertheless, the simple expressions capture global patterns to first order. The model provides a mechanistic upper estimate on global chemoautotrophic carbon fixation of 0.2–0.5 Pg C yr<span class="inline-formula"><sup>−1</sup></span>, which is on the low end of the wide range of previous estimates. Modeled carbon fixation by AOA (0.2–0.3 Pg C yr<span class="inline-formula"><sup>−1</sup></span>) exceeds that of NOB (about 0.1 Pg C yr<span class="inline-formula"><sup>−1</sup></span>) because of the higher biomass yield of AOA. The simple expressions derived here can be used to quantify the biogeochemical impacts of additional metabolic pathways (i.e., mixotrophy) of nitrifying clades and to identify alternative metabolisms fueling carbon fixation in the deep ocean.</p> |
| first_indexed | 2024-04-13T12:51:07Z |
| format | Article |
| id | doaj.art-5086292fcb6b44459d8beb8b19746213 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-04-13T12:51:07Z |
| publishDate | 2022-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-5086292fcb6b44459d8beb8b197462132022-12-22T02:46:12ZengCopernicus PublicationsBiogeosciences1726-41701726-41892022-12-01195401541810.5194/bg-19-5401-2022Controls on the relative abundances and rates of nitrifying microorganisms in the oceanE. J. Zakem0E. J. Zakem1B. Bayer2W. Qin3A. E. Santoro4Y. Zhang5Y. Zhang6N. M. Levine7Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, USADepartment of Biological Sciences, University of Southern California, Los Angeles, CA, USADepartment of Microbiology and Ecosystem Science, University of Vienna, Vienna, AustriaDepartment of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USADepartment of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, USAState Key Laboratory of Marine Environmental Science and College of Ocean and Earth Sciences, Xiamen University, Xiamen, ChinaCollege of Ocean and Earth Sciences, Xiamen University, Xiamen, ChinaDepartment of Biological Sciences, University of Southern California, Los Angeles, CA, USA<p>Nitrification controls the oxidation state of bioavailable nitrogen. Distinct clades of chemoautotrophic microorganisms – predominantly ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) – regulate the two steps of nitrification in the ocean, but explanations for their observed relative abundances and nitrification rates remain incomplete and their contributions to the global marine carbon cycle via carbon fixation remain unresolved. Using a mechanistic microbial ecosystem model with nitrifying functional types, we derive simple expressions for the controls on AOA and NOB in the deep, oxygenated open ocean. The relative biomass yields, loss rates, and cell quotas of AOA and NOB control their relative abundances, though we do not need to invoke a difference in loss rates to explain the observed relative abundances. The supply of ammonium, not the traits of AOA or NOB, controls the relatively equal ammonia and nitrite oxidation rates at steady state. The relative yields of AOA and NOB alone set their relative bulk carbon fixation rates in the water column. The quantitative relationships are consistent with multiple in situ datasets. In a complex global ecosystem model, nitrification emerges dynamically across diverse ocean environments, and ammonia and nitrite oxidation and their associated carbon fixation rates are decoupled due to physical transport and complex ecological interactions in some environments. Nevertheless, the simple expressions capture global patterns to first order. The model provides a mechanistic upper estimate on global chemoautotrophic carbon fixation of 0.2–0.5 Pg C yr<span class="inline-formula"><sup>−1</sup></span>, which is on the low end of the wide range of previous estimates. Modeled carbon fixation by AOA (0.2–0.3 Pg C yr<span class="inline-formula"><sup>−1</sup></span>) exceeds that of NOB (about 0.1 Pg C yr<span class="inline-formula"><sup>−1</sup></span>) because of the higher biomass yield of AOA. The simple expressions derived here can be used to quantify the biogeochemical impacts of additional metabolic pathways (i.e., mixotrophy) of nitrifying clades and to identify alternative metabolisms fueling carbon fixation in the deep ocean.</p>https://bg.copernicus.org/articles/19/5401/2022/bg-19-5401-2022.pdf |
| spellingShingle | E. J. Zakem E. J. Zakem B. Bayer W. Qin A. E. Santoro Y. Zhang Y. Zhang N. M. Levine Controls on the relative abundances and rates of nitrifying microorganisms in the ocean Biogeosciences |
| title | Controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| title_full | Controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| title_fullStr | Controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| title_full_unstemmed | Controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| title_short | Controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| title_sort | controls on the relative abundances and rates of nitrifying microorganisms in the ocean |
| url | https://bg.copernicus.org/articles/19/5401/2022/bg-19-5401-2022.pdf |
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