Effluents from desalination technologies may influence natural bacterial assemblages due to changes in salinity, pH, dissolved organic carbon concentration (DOC), DOC quality and cellular hydrostatic pressure. Salinity, pH, and pressure change effects on heterotrophic bacterial production (as measured by leucine incorporation) were examined in experiments with surface water from the Delaware Bay, Atlantic Ocean and Pacific Ocean. Bacterial production decreased by 57–67% when salinity of Atlantic Ocean and Delaware Bay surface water samples were increased from ambient to 60PSU. Decreasing ambient seawater pH from 8.0 to below 5.0 with CO2 gas reduced production by 96–100%. Decreasing seawater pH by 1.5units at 33PSU caused equivalent inhibition to increasing salinity by 27PSU (pH 8.0). Bacterial production in Pacific Ocean surface water pressurized for 72h was decreased 40% by increasing salinity, when measured 1h after decompression. However, production increased 43% with increasing salinity when measured 24h after decompression. One explanation for these divergent effects between the 1- and 24-h sampling at ambient pH may be community adaptation. Strains amongst the natural assemblage that survived the pressurization by saturating their membrane phospholipids would likely be better adapted to compete for available nutrients under elevated salinity.