THE OCCURRENCE OF MARINE ORGANISMS - IN BALLAST WATER OF SHIP VISITING COLOMBO HARBOUR

Abstract

Ballast water is a major source of biological invasions around the globe. More than 4500 bulk carriers, cargovessels and oil tankers arrive to Colombo harbor annually and they discharge a large amount of ballast waterin Sri Lankan marine environment. Present research was to study the occurrence of marine organisms in theballast water of ships visiting Colombo harbour. Ballast water samples were taken from ships visited toColombo harbor from different ports in Indian Ocean. The species densities were recorded. In additionbiological oxygen demand, chlorophyll-a, conductivity, dissolved oxygen, nitrate, pH, orthophosphate,salinity, and temperature were measured in the sample. The vital status (live and dead) of the zooplanktonspecies studied was ascertained using neutral red staining techniques. Thirty-three plankton species wererecorded in ballast water samples which included fourteen copepods, eight dinoflagllates, eight diatoms, oneprotozoan, one rotifer, and one mollusc. Highest density was recorded for Thalassionema sp. and lowestdensity was recorded for unidentified species belong to family Tintinnidae and gastropod veliger larvae.Ceratium furca, Ceratium fusus, Peridinium sp., Protoperidinium grande, Protoperidinium obtusum,andProtoperidinium robustum were the six species of potentially harmful red tide forming dinoflagllates whichwere recorded during the study. Neutral red staining technique revealed that there were no live zooplanktonspecies in the ballast water samples. According to the Pearson Correlation there were strong positive linearrelationships between species density with nitrate (r2= 0.845) and orthophosphate (r2= 0.800) levels and alsopH (r2=0.694) had slightly positive linear relationships with species density. The temperature (r2=-0.758)had negative linear relationship with species density.Keywords: ballast water, Colombo harbor, plankton species, staining technique, physico-chemicalparameters