Accidental introduction of alien plankton into the Sri Lankan coastal zone through ballast water of cargo ships

Abstract

Accidental introduction of alien plankton through ballast water is a major ecological issue in many countries in the world. As there are no local studies addressing this problem, the present study was carried out to see whether alien plankton are introduced into Sri Lankan coastal zone through ballast water. Marine plankton occurring within ballast water holds of five cargo ships arrived at Colombo harbour and three local sites including Colombo inner harbour and two neighboring coastal sites were sampled. The physico-chemical parameters of water samples were also measured. Data on species abundance and physico-chemical parameters were analyzed using multivariate and univariate statistical tests as appropriate. Altogether 159 taxa of plankton were found in the samples. In the ballast water samples alone, there were 56 different taxa of which 50% of them were totally alien to the local coastal zone. The physico-chemical parameters of water samples between the four sites were not significantly different. However, multivariate statistical tests confirmed that the plankton community of the ballast water samples was significantly different from that of the three local sites. Considering the large number of ships calling annually at Colombo harbour, the great potential of accidental introduction of alien plankton into the Sri Lankan coastal zone should never be underestimated.