This dataset includes results obtained from a one-year monitoring survey (from May 1984 to April 1985) of physico-chemical parameters in marine water of the Mar Piccolo of Taranto. Sampling was carried out monthly, for a total of 12 months in fifteen stations of the first inlet and ten stations of the second inlet of the Mar Piccolo of Taranto. Marine water was collected at three different depth in each sampling site: surface, middle and bottom. The selected parameters of this study were: pH, temperature, dissolved oxygen, salinity, ortho-phosphate, ammonia, nitrites and nitrates. Monthly monitoring survey in marine water represents a useful tool to evaluate seasonal changes in water parameters. Nutrients in fact represent the major sources of nutrition for phytoplankton growth in seawater (with sunlight and inorganic carbon) and increased nutrient inputs could lead to an increase in production and possible eutrophication phenomena