Study on spatial and temporal variations of planktobacteria quantity in Apostichopus japonicus culture ponds during autumn and winter

Abstract:

he spatial and temporal variations of planktobacteria quantity in Apostichopus japonicus culture ponds during autumn and winter(from September,2008 to Februray,2009)were investigated by plate culture and fluorescence microscope techniques.The total number of planktobacteria estimated by acridine orange direct count(AODC)and Direct Viable Count(DVC)ranged in 1.0×106~2.1×107 cell/ml and 4.0×105~5.7×106 cell/ml,respectively.The amount of heterotrophic bacteria detected by heterotrophic plate count(HPC)ranged from 0.6×102 to 1.66×105CFU/ml.The amount of Vibrio was below 6.6×103CFU/ml using TCBS selective medium cultivation.The number of planktobacteria varied in different season,which reached the maximum in October and the minimum in January.The number of bacteria in the ponds was significantly higher in autumn than in winter(P<0.01).The total number of bacteria in different water layers was determined.The results showed that the total number of bacteria in the bottom water was significantly higher than that in the surface water(P<0.05).There was significant correlation(P<0.01)between data deduced by using different bacterial count methods.