Abstract: Metabolism of bacterial carbon in shrimp cultural enclosure ecosystems was studied from June 6 to August 24 , 1997 in the shrimp farm of Huanghai Fisheries Group Corporation .The results were :the average rates of respiration , production and detritus decomposition (μgC/L·d)of bacterioplankton were 349 ±167 , 180 ±86 and 529 ±253 respectively .The bacterioplankton respiration was 40 percent of the plankton community respiration .The rates of respiration , production and detritus decomposition (μgC/L·d)of sediment bacteria were 168 .07 , 72 .27 and 240 .34 respectively .There were significant correlation between the sediment respiration and the sediment temperature , bacteria biomass and organic carbon concentration .The respiration rate of certain numbers of sediment bacteria showed significant negative correlation with total sediment bacteria biomass , which proved that the metabolism of the sediment bacteria was probably limited by inadequate substrate supply .The respiration , production and detritus decomposition of the bacterioplankton were 2 .08 , 2 .49 and 2 .20 times higher than that of the sediment bacteria in the cultural period .The bacterioplankton and sediment bacteria decomposed 30 percent of the organic carbon income of the enclosure in total , in which , 10 percent was transformed into bacterial carbon and 20 percent was mineralized .