A simple and highly reproducible technique to measure the bacterial respiration of ¹⁴C-labeled compounds in seawater samples

C. Tamburini^* & M. Tedetti

 Laboratoire Microbiologie Marine, UMR 6117 CNRS – INSU & Université de la Méditerranée, COM, Campus de Luminy, Case 907, 13288 Marseille, Cedex 9, France

*E-mail: ctambu@com.univ-mrs.fr  

Hydrobiologia (2004), 523: 1-7

Abstract: Production of ¹⁴CO₂ from water samples amended with ¹⁴C-labeled molecules allows to estimate the mineralization rates of a variety of organic compounds. Diverse protocols have been already proposed for ¹⁴CO₂ extraction and trapping. Yet, efficiency of carbon dioxide recovery greatly varies and, despite the application of operators, data from duplicate samples are often divergent. In order to propose a standardized protocol and to avoid the main source of artifacts, we suggest to keep the trapping agent for ¹⁴CO₂ directly into a 20 ml scintillation vial hanging in the degassing bottle. To validate this protocol, we plotted the radioactivity (disintegration per minute) due to ¹⁴CO₂ recovered after acidification of 42 seawater samples supplemended with sodium (¹⁴C)-bicarbonate (NaH¹⁴CO₃) against the actual radioactivity of the corresponding added bicarbonate solutions. Efficiency of this protocol results satisfactory, as for these 42 assays the percentage of recovery is equal to 99 % with a very low variability (± 1 %, p=0.05).

Key words: Bacteria, respiration, mineralization, decarbonatation, technique, carbon dioxide, seawater.