The bacteria involved in nitrogen and sulphur cycles and physicochemical characteristics of water
and sediment in traditional, modified extensive and semi-intensive shrimp culture systems of West
Bengal, India were monitored. The physicochemical parameters, except salinity and sediment pH,
were observed to be well within the optimum levels recommended for shrimp culture. The levels of
ammonia (NH3; PV0.05) and nitrite (NO2; Pb0.03) differed significantly among systems. The mean
heterotroph counts were always close to or above 106/ml pond water and 106/g sediment. The counts
of total heterotrophs and nitrate reducing bacteria (NRB) of the pond water of different culture
systems differed significantly ( Pb0.01). While the counts of nitrite oxidizing bacteria (NOB;
Pb0.001), nitrate reducing bacteria ( Pb0.01) and sulphate reducing bacteria (SRB; Pb0.03) in pond
sediment of the three culture systems differed significantly. The mean counts of ammonia oxidizers
increased with days of culture (DOC) in traditional and modified extensive systems, but they
remained constant in semi-intensive pond sediment. The mean counts of nitrite oxidizers were
generally high in water and sediment samples of modified extensive system. The mean sulphur
oxidizing bacterial counts of pond water were higher in semi-intensive and modified extensive
systems, which generally decreased with increasing DOC. The sulphate reducing bacterial counts of
sediment increased with DOC in modified extensive and semi-intensive systems and vice versa i