skip to main content

DOE PAGESDOE PAGES

Title: Modest net autotrophy in the oligotrophic ocean

The metabolic state of the oligotrophic subtropical ocean has long been debated. Net community production (NCP) represents the balance of autotrophic carbon fixation with heterotrophic respiration. Many in vitro NCP estimates based on oxygen incubation methods and the corresponding scaling relationships used to predict the ecosystem metabolic balance have suggested the ocean gyres to be net heterotrophic; however, all in situ NCP methods find net autotrophy. Reconciling net heterotrophy requires significant allochthonous inputs of organic carbon to the oligotrophic gyres to sustain a preponderance of respiration over in situ production. Here we use the first global ecosystem-ocean circulation model that contains representation of the three allochthonous carbon sources to the open ocean, to show that the five oligotrophic gyres exhibit modest net autotrophy throughout the seasonal cycle. Annually integrated rates of NCP vary in the range ~1.5–2.2 mol O 2 m -2 yr -1 across the five gyre systems; however, seasonal NCP rates are as low as ~1 ± 0.5 mmol O2 m -2 d -1 for the North Atlantic. Volumetric NCP rates are heterotrophic below the 10% light level; however, they become net autotrophic when integrated over the euphotic zone. Observational uncertainties when measuring these modest autotrophic NCP ratesmore » as well as the metabolic diversity encountered across space and time complicate the scaling up of in vitro measurements to the ecosystem scale and may partially explain the previous reports of net heterotrophy. The oligotrophic ocean is autotrophic at present; however, it could shift toward seasonal heterotrophy in the future as rising temperatures stimulate respiration.« less
Authors:
ORCiD logo [1] ;  [1]
  1. Univ. of California, Irvine, CA (United States). Earth System Science
Publication Date:
Grant/Contract Number:
SC0012550
Type:
Accepted Manuscript
Journal Name:
Global Biogeochemical Cycles
Additional Journal Information:
Journal Volume: 31; Journal Issue: 4; Journal ID: ISSN 0886-6236
Publisher:
American Geophysical Union (AGU)
Research Org:
Univ. of California, Irvine, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; net community production; metabolic state; oligotrophic gyres; autotrophic; heterotrophic
OSTI Identifier:
1465338
Alternate Identifier(s):
OSTI ID: 1402335

Letscher, Robert T., and Moore, J. Keith. Modest net autotrophy in the oligotrophic ocean. United States: N. p., Web. doi:10.1002/2016GB005503.
Letscher, Robert T., & Moore, J. Keith. Modest net autotrophy in the oligotrophic ocean. United States. doi:10.1002/2016GB005503.
Letscher, Robert T., and Moore, J. Keith. 2017. "Modest net autotrophy in the oligotrophic ocean". United States. doi:10.1002/2016GB005503. https://www.osti.gov/servlets/purl/1465338.
@article{osti_1465338,
title = {Modest net autotrophy in the oligotrophic ocean},
author = {Letscher, Robert T. and Moore, J. Keith},
abstractNote = {The metabolic state of the oligotrophic subtropical ocean has long been debated. Net community production (NCP) represents the balance of autotrophic carbon fixation with heterotrophic respiration. Many in vitro NCP estimates based on oxygen incubation methods and the corresponding scaling relationships used to predict the ecosystem metabolic balance have suggested the ocean gyres to be net heterotrophic; however, all in situ NCP methods find net autotrophy. Reconciling net heterotrophy requires significant allochthonous inputs of organic carbon to the oligotrophic gyres to sustain a preponderance of respiration over in situ production. Here we use the first global ecosystem-ocean circulation model that contains representation of the three allochthonous carbon sources to the open ocean, to show that the five oligotrophic gyres exhibit modest net autotrophy throughout the seasonal cycle. Annually integrated rates of NCP vary in the range ~1.5–2.2 mol O2 m-2 yr-1 across the five gyre systems; however, seasonal NCP rates are as low as ~1 ± 0.5 mmol O2 m-2 d-1 for the North Atlantic. Volumetric NCP rates are heterotrophic below the 10% light level; however, they become net autotrophic when integrated over the euphotic zone. Observational uncertainties when measuring these modest autotrophic NCP rates as well as the metabolic diversity encountered across space and time complicate the scaling up of in vitro measurements to the ecosystem scale and may partially explain the previous reports of net heterotrophy. The oligotrophic ocean is autotrophic at present; however, it could shift toward seasonal heterotrophy in the future as rising temperatures stimulate respiration.},
doi = {10.1002/2016GB005503},
journal = {Global Biogeochemical Cycles},
number = 4,
volume = 31,
place = {United States},
year = {2017},
month = {4}
}