Phytoplankton Carbon Fixation Gene (RuBisCO) Transcripts and Air-sea CO₂ Flux in the Mississippi River Plume

Authors

David E. John, University of South Florida
Zhaohui A. Wang, University of South Florida
Xuewu Liu, University of South FloridaFollow
Robert H. Byrne, University of South FloridaFollow
Jorge E. Corredor, University of Puerto Rico
José M. López, University of Puerto Rico
Alvaro Cabrera, University of Puerto Rico
Deborah A. Bronk, Virginia Institute of Marine Science
F Robert Tabita, The Ohio State University
John H. Paul, University of South Florida

Document Type

Article

Publication Date

2007

Keywords

Life Sciences, general, Microbiology, Ecology, Evolutionary Biology, Microbial Genetics and Genomics, Microbial Ecology

Digital Object Identifier (DOI)

https://doi.org/10.1038/ismej.2007.70

Abstract

River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO₂ drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO₂ dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO₂ in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30–32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, α-Synechococcus or high-light Prochlorococcus. However, rbcL transcript abundances were similar among these groups at oligotrophic stations (salinity 34–36). Diatom cell counts and heterokont rbcL RNA showed a strong negative correlation to seawater pCO₂. While Prochlorococcus cells did not exhibit a large difference between low and high pCO₂ water, Prochlorococcus rbcL RNA concentrations had a strong positive correlation to pCO₂, suggesting a very low level of RuBisCO RNA transcription among Prochlorococcus in the plume waters, possibly due to their relatively poor carbon concentrating mechanisms (CCMs). These results provide molecular evidence that diatom/pelagophyte productivity is largely responsible for the large CO₂ drawdown occurring in the MRP, based on the co-occurrence of elevated RuBisCO gene transcript concentrations from this group and reduced seawater pCO₂ levels. This may partly be due to efficient CCMs that enable heterokont eukaryotes such as diatoms to continue fixing CO₂ in the face of strong CO₂ drawdown. Our work represents the first attempt to relate in situ microbial gene expression to contemporaneous CO₂ flux measurements in the ocean.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

The ISME Journal, v. 1, p. 517-531

Scholar Commons Citation

John, David E.; Wang, Zhaohui A.; Liu, Xuewu; Byrne, Robert H.; Corredor, Jorge E.; López, José M.; Cabrera, Alvaro; Bronk, Deborah A.; Tabita, F Robert; and Paul, John H., "Phytoplankton Carbon Fixation Gene (RuBisCO) Transcripts and Air-sea CO₂ Flux in the Mississippi River Plume" (2007). Marine Science Faculty Publications. 1753.
https://digitalcommons.usf.edu/msc_facpub/1753