Response of bacterioplankton to iron fertilization

• Main Authors: Jesús M. Arrieta, Markus G. Weinbauer, Carolien Lute, Gerhard J. Herndl
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Southern Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.521.5133; http://www.aslo.org/lo/toc/vol_49/issue_3/0799.pdf

We studied the bacterial response to Fe fertilization over 3 weeks during the second iron-enrichment experiment (EisenEx) in the Southern Ocean. Bacterial abundance in the Fe-fertilized patch increased over the first 12 d following Fe release and remained about twice as high as outside the Fe-fertilized patch until the end of the experiment. Bacterial production peaked a few days after each of the three Fe releases inside the Fe-fertilized patch, reaching rates two to three times higher than outside the patch. Besides the peaks in leucine and thymidine incor-poration following Fe release, bacterial production was not significantly higher inside the patch than outside, sug-gesting direct limitation of bacterial growth by Fe. Bacterial aminopeptidase activity roughly followed the increase in bacterial abundance, whereas cell-specific a- and b-glucosidase were higher inside the Fe-fertilized patch. The diversity of b-glucosidases was determined by capillary electrophoresis zymography. The different b-glucosidases showed much higher activity levels inside the patch than in the surrounding waters, and three additional b-gluco-sidases constituting;55 % of the total b-glucosidase activity were present inside the Fe-fertilized patch from day 9 onward. No major changes in response to Fe fertilization were detected in the phylogenetic composition of the bacterioplankton community, as determined by 16S rDNA fingerprinting, indicating a remarkable adaptation of the bacterioplankton community to episodic iron inputs. This stability on the phylogenetic level is contrasted by the