TABLE 1.

Comparison of heterotrophic bacterial biomass production, respiration, and bacterial growth efficiency in the control and enriched microcosms integrated during the last 24 h of the microcosm experimentc

CharacteristicControl microcosmsEnriched microcosms
C1C2NUT1NUT2
BBP (μM C)0.240.303.053.04
Respiration (μM O2)2.462.807.908.73
BGEa0.090.100.280.26
DMSP contribution to C demand (%)6554
[35S]DMSP sulfur assimilation efficiency into TCA insolubles (%)29291312
DMSP contribution to S demand (%)b86069010295
  • a Assuming the BGE = BBP/(BBP + respiration), a respiratory quotient of 1, and that nonbacterial respiration was negligible. If nonbacterial respiration was significant, actual bacterial growth efficiencies would be higher than calculated. BBP, bacterial biomass production; BGE, bacterial growth efficiency.

  • b Assuming a C:S ratio of 240 (2).

  • c Also shown is the proportion of the bacterial C and S demands that could be derived from the measured DMSP consumption rates.