Science Serving Maryland's Coasts
Roger Newell, Ph.D., Paul del Giorgio, Ph.D.
Horn Point Laboratory
Patterns in Bacterioplankton Respiration and Respiratory Quotients
Water samples from a fish farm in Princess Anne, MD were used as inoculum to filtered Choptank River water, to which were added five different treatments of nutrients Twice a week from June 20 to July 24, 1998, samples of the mixtures were 8 pm filtered to eliminate all heterotrophic organisms except planktonic bacteria. All the water samples were incubated for 24h in gas tight glass flasks. Aliquots were taken at intervals and analyzed for oxygen and carbon dioxide concentrations, bacterial production, and nutrient content in order to calculate values for respiratory quotients (RQ) and bacterial growth efficiencies (BGE). Variations in both RQ and BGE were seen over the course of the experiments as well as by treatment. The empirically based values of BGE were compared to BGE calculated with an assumed constant RQ of one. The comparison indicates a similar overall pattern by day and by treatment. However, variations between the two techniques show that using a constant RQ can lead to either an over- or under-estimation of the amount of bacterial production that indicates the importance planktonic bacteria in an aquatic ecosystem and in turn, skew the estimate of total carbon production in that system.
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