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Aquatic Microbial Ecology

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AME 50:239-250 (2008)  -  DOI:

Carbon cycling by microbes influenced by light in the Northeast Atlantic Ocean

Matthew T. Cottrell1, Vanessa K. Michelou1, Nina Nemcek2,4, Giacomo DiTullio3, David L. Kirchman1,*

1College of Marine and Earth Studies, University of Delaware, Lewes, Delaware 19958, USA
2University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
3College of Charleston, Charleston, South Carolina 29424, USA
4Present address: Institute of Ocean Sciences, Sidney, British Columbia V8L 4B2, Canada
*Corresponding author. Email:

ABSTRACT: The goal of this study was to examine the relationships between phytoplankton and heterotrophic bacteria and the effect of light on bacterial growth and respiration in the Northeast Atlantic Ocean in summer. Heterotrophic microbes were a substantial component of the plankton as indicated by the ratio of bacterial biomass to phytoplankton biomass, which varied from 0.15 to 0.83, averaging 0.60. Aerobic anoxygenic phototrophic (AAP) bacteria made up on average 10% of bacterial abundance and 13% of bacterial biomass. AAP bacterial biomass was on average 2-fold higher than Synechococcus sp. biomass, whereas Prochlorococcus sp. was never more than 1% of bacterial biomass. The bacterial production to primary production ratio ranged from 0.04 to 0.14 and was on average 0.07. The bacterial growth efficiency (BGE) in light incubations (10%) was 3-fold lower than in the dark (32%). Consequently, the calculated flux of carbon through bacteria in the light was also about 3-fold lower in the dark, since ratios of bacterial carbon demand (BCD) to primary production inferred from light and dark estimates of BGE were 0.7 and 0.2, respectively. However, BCD and respiration rates were not greater than primary production, suggesting that this region of the North Atlantic was net autotrophic even after the spring bloom. The BGE data and the abundance of photoheterotrophic microbes, such as AAP bacteria, highlight the importance of the effects of light on carbon cycling by bacteria in the Northeast Atlantic Ocean.

KEY WORDS: Photoheterotrophy · Light · Respiration · Bacterial growth efficiency · Spring bloom

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Cite this article as: Cottrell MT, Michelou VK, Nemcek N, DiTullio G, Kirchman DL (2008) Carbon cycling by microbes influenced by light in the Northeast Atlantic Ocean. Aquat Microb Ecol 50:239-250.

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