the application of a plugflow reactor to measure the biodegradable dissolved organic carbon bdoc in seawater most of the ambient dissolved organic carbon doc is refractory to microbial degradation bacteria can consume a minor but variable part of the doc pool over periods of hours and days it is important to increase our knowledge of the dynamics of the biodegradable fraction of doc bdoc to understand the global carbon budget several methods for determining bdoc have been developed however the problem of most of them is the time daysweeks required for the colonization andor determination in this paper we describe the application to seawater of a plugflow bioreactor to measure bdoc within 34 h the bioreactor was built following sndergaard and worm sndergaard m worm j 2001 measurement of biodegradable dissolved organic carbon bdoc in lake water with a bioreactor water res 35 25052513 protocols for the measurement of bdoc in lake water we analyzed bdoc on samples collected in the gulf of trieste during autumnwinter and summer 20032004 bdoc concentrations varied from 8 to 24 microm and represented from 103 to 255 of the total doc to evaluate the effectiveness of this method we compared bioreactor bdoc measurement with data obtained from batch cultures the results indicate that bdoc in coastal seawater can be measured rapidly and reliably with this bioreactor