WATER-QUALITY AND BACTERIAL-POPULATIONS IN A TROPICAL MARINE CAGE CULTURE FARM

A study was conducted to investigate fluctuations in different physica l and chemical parameters, and bacterial populations in a tropical mar ine cage culture farm for one annual cycle. Samples were collected fro m the centre of the farm (station 1) and away from the cages (station 2), There were no significant differences (P > 0.05) in water quality parameters, such as temperature, salinity, dissolved oxygen, conductiv ity and pH between the two stations during the neap and spring tides. Nutrient concentrations and bacterial counts were slightly higher at s tation 1 than station 2, but the differences were not significant (P > 0.05). In general, nutrients and chlorophyll a concentrations in the study area were higher than those reported in the pristine marine envi ronment. There were significant correlations (P < 0.05) between some n utrients (soluble reactive phosphorus, nitrite and nitrate) and bacter ial counts, There were no significant differences P > 0.05) in nutrien t levels and bacterial populations between the neap and spring tides, probably because of the large number of farms operating in the shallow channel. The present study indicates that high organic loading from t he fish farming activities could cause deterioration of the water qual ity in the cage-culture system as well as in the surrounding environme nt.