Determination of conversion factors for estimation of subantarctic marine bacterial production measured by 3H-thymidine incorporation methodology

Abstract

In order to determine conversion factors for H-3-thymidine incorporation to bacterial growth rate, we performed a series of seawater culture experiments on surface mixed layer samples in a subantarctic coastal area. Four different treatments were used: bacterivory reduction (dilution or filtration), nutrient enrichment and temperature increase. Conversion factors were estimated by the 'integration approach': the increase in bacterial biomass (biomass at final time point minus initial value) was divided by incorporation rates integrated over time during the experiment. Both bacterial abundance and mean cell volumes markedly increased in all experiments. The manipulation effects were strongest in the high temperature batch compared with the other experiments. However, the 4 different treatments yielded comparable conversion factors ranging from 9.7 x 10(5) to 1.5 x 10(6) cells pmol(-1) with a mean value of 1.2 x 10(6) cells pmol(-1).