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. DOI: 10.4038/sljas.v14i0.2202Sri Lanka J. Aquat. Sci. 14 (2009): 86-103
Highlights
Invasion of alien organisms through ballast water is one of the four greatest threats to the world's oceans as it has been estimated that approximately 70,000 cargo vessels of the world are transporting about 10 billion tons of ballast water globally per year indicating a global concern for this problem (Stewart 1991)
It has been estimated that at any one time in excess of 3,000 species are in motion in the ballast water tanks of ocean going ships around the world (Carlton and Geller 1995) and a total of several thousands or even millions of organisms are transported in the ballast water holds of a single ship (Locke et al 1993)
As the oceanic currents are generally northbound in the west coast (Jayaweera 1999), it was hypothesized that these alien plankton would drift with the ocean currents and there after found in northern locations so that the second sampling site was selected in the Pamunugama coast (Latitude 7o 05' N; Longitude 79o 49 ́ E) which is situated about 30 km north to the Colombo harbour
Summary
Invasion of alien organisms through ballast water is one of the four greatest threats to the world's oceans as it has been estimated that approximately 70,000 cargo vessels of the world are transporting about 10 billion tons of ballast water globally per year indicating a global concern for this problem (Stewart 1991). Medcof 1975; Carlton 1985 and 1987; Vinogradov et al 1989; Shushkina and Musayeva 1990; Hallegraeff and Bolch 1991; Reeve 1993; Subba Rao et al 1994). Much of these alien palnkton cause ecological imbalances and lead into severe economic losses to their receiving countries through their invasiveness. For example the zebra mussel, an invasive mollusc species accidentally introduced via ballast water as a plankton, caused billions of dollars of damage by fouling underwater pipes in the Great Lakes in the USA (Roberts 1990; Lodge 1993; Gollasch 1997)
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