AME 55:169-187 (2009)  -  DOI: https://doi.org/10.3354/ame01287

Significance of diatom-derived polymers in carbon flow dynamics within estuarine biofilms determined through isotopic enrichment

B. J. Bellinger1,4, G. J. C. Underwood2, S. E. Ziegler3, M. R. Gretz1,*

1Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931-1295, USA
2Department of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, UK
3Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X5, Canada
4Present address: Soil and Water Science Department, University of Florida, Gainesville, Florida 32611, USA
*Corresponding author. Email:

ABSTRACT: Pennate diatoms are the main group of primary producers in transient microbial biofilms at the sediment surface in muddy intertidal systems. These microalgae produce a substantial quantity of extracellular polymeric substances (EPS) that contribute significantly to the cohesive properties observed in biofilms. Changes in carbohydrate content and composition and the persistence of diatom EPS were demonstrated with pulse-chase NaH13CO3 labeling and simultaneous detection of isotopic enrichment in polysaccharides and phospholipid fatty acids (PLFAs) in Colne Estuary, UK, biofilms over a 48 h period. Significant isotopic enrichment of glucan indicated that a large proportion of fixed carbon was initially sequestered into intracellular chrysolaminaran, and labeled carbon was also quickly used for production of the diatom PLFA 20:5ω3 and EPS. Saccharides in the EPS fractions were enriched rapidly, followed by labeling of distinct bacterial PLFAs through heterotrophic utilization of EPS within 4 h. Maximal isotopic enrichment of diatom and Gram-negative bacterial PLFAs and hot water- and hot bicarbonate-soluble EPS fractions occurred after 4 h, and 13C-labeling increased in Gram-positive bacterial PLFAs throughout the study period. After 48 h, PLFAs remained highly labeled relative to diatom-derived polysaccharides, indicating persistence of assimilated C in organisms within the biofilms through time and rapid turnover of polysaccharide pools within the biofilms. Coupled pulse-chase isotopic labeling and simultaneous tracking of 13C in polysaccharides and PLFAs directly demonstrated the flow of carbon between biofilm autotrophs and heterotrophic bacteria and the significance of diatom-derived carbohydrates in this exchange.


KEY WORDS: EPS · PLFA · Isotopic enrichment · Carbon pathways · Biofilms


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Cite this article as: Bellinger BJ, Underwood GJC, Ziegler SE, Gretz MR (2009) Significance of diatom-derived polymers in carbon flow dynamics within estuarine biofilms determined through isotopic enrichment. Aquat Microb Ecol 55:169-187. https://doi.org/10.3354/ame01287

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