MEPS 577:49-65 (2017)  -  DOI: https://doi.org/10.3354/meps12243

Interactive effects of elevated temperature and CO2 on nitrate, urea, and dissolved inorganic carbon uptake by a coastal California, USA, microbial community

Jenna L. Spackeen1,*, Rachel E. Sipler1, Kai Xu2, Avery O. Tatters2, Nathan G. Walworth2, Erin M. Bertrand3,4,5, Jeffrey B. McQuaid4,5, David A. Hutchins2, Andrew E. Allen4,5, Deborah A. Bronk

1Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Point, VA 23062, USA
2The University of Southern California, Department of Biological Sciences, 3616 Trousdale Parkway, Los Angeles, CA 90089, USA
3Department of Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
4Microbial and Environmental Genomics, J. Craig Venter Institute, La Jolla, CA 92037, USA
5Integrative Oceanography Division, Scripps Institution of Oceanography, UC San Diego, La Jolla, CA 92037, USA
*Corresponding author:

ABSTRACT: Average global temperatures and carbon dioxide (CO2) levels are expected to increase in the coming decades. Implications for ocean ecosystems include shifts in microbial community structure and subsequent modifications to nutrient pathways. Studying how predicted future temperature and CO2 conditions will impact the biogeochemistry of the ocean is important because of the ocean’s role in regulating global climate. We determined how elevated temperature and CO2 affect uptake rates of nitrate, urea, and dissolved inorganic carbon (DIC) by 2 size classes (0.7-5.0 and >5.0 µm) of a microbial assemblage collected from coastal California, USA. This microbial community was incubated for 10 d using an ecostat continuous culture system that supplied the microorganisms with either nitrate or urea as the dominant nitrogen source. Biomass parameters, nutrient concentrations, and uptake rates were measured throughout the experiment. In all treatments, urea uptake rates were greater than nitrate, and larger microorganisms had higher uptake rates than smaller microorganisms. Uptake rates of urea and DIC within both size fractions were higher at elevated temperature, and uptake rates of nitrate by smaller microorganisms increased with elevated CO2. These findings suggest that the rate at which nutrients cycle in temperate coastal waters will increase as temperature and CO2 levels rise and that the effect will vary between nitrogen substrates and different microorganisms.


KEY WORDS:  Nitrate · Urea · DIC · Uptake · Temperature · CO2 · Southern California Bight · Microbial communities


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Cite this article as: Spackeen JL, Sipler RE, Xu K, Tatters AO and others (2017) Interactive effects of elevated temperature and CO2 on nitrate, urea, and dissolved inorganic carbon uptake by a coastal California, USA, microbial community. Mar Ecol Prog Ser 577:49-65. https://doi.org/10.3354/meps12243

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