Sustainable Ocean Resources Network

Abstract

Ballast water is a major source of biological invasions around the globe. More than 4500 bulk carriers, cargo vessels and oil tankers arrive to Colombo harbor annually and they discharge a large amount of ballast water in Sri Lankan marine environment. Present research was to study the occurrence of marine organisms in the ballast water of ships visiting Colombo harbour. Ballast water samples were taken from ships visited to Colombo harbor from different ports in Indian Ocean. The species densities were recorded. In addition biological 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 zooplankton species studied was ascertained using neutral red staining techniques. Thirty-three plankton species were recorded in ballast water samples which included fourteen copepods, eight dinoflagllates, eight diatoms, one protozoan, one rotifer, and one mollusc. Highest density was recorded for Thalassionema sp. and lowest density was recorded for unidentified species belong to family Tintinnidae and gastropod veliger larvae. Ceratium furca, Ceratium fusus, Peridinium sp., Protoperidinium grande, Protoperidinium obtusum,and Protoperidinium robustum were the six species of potentially harmful red tide forming dinoflagllates which were recorded during the study. Neutral red staining technique revealed that there were no live zooplankton species in the ballast water samples. According to the Pearson Correlation there were strong positive linear relationships between species density with nitrate (r 2 = 0.845) and orthophosphate (r 2 = 0.800) levels and also pH (r 2 =0.694) had slightly positive linear relationships with species density. The temperature (r 2 =-0.758) had negative linear relationship with species density.