Abstract:
Accidental introduction of alien invasive species through ballast water discharges from
ships has raised global attention as a major cause of marine invasions. Colombo harbour
facilitates a large number of ships annually and a great amount of ballast water is
discharged into the harbour during deballasting operations. The present study was
carried out to identify variation of plankton assemblages in ballast water of ships arrived
at Colombo harbor, and Western coastal area of Sri Lanka in order to identify possible
introductions of marine planktons through ballast water. Plankton samples were collected
from five ships arrived at Colombo harbour and three local sites including Colombo
harbour, Panadura and Pamunugama. Physical and chemical parameters including water
temperature, pH, turbidity, salinity, Electrical conductivity, total dissolved solids, nitrate
and orthophosphate were also recorded at sampling locations. Plankton assemblages of
local sites and ballast water were evaluated using univariate and multivariate statistical
tests.
A total of 126 plankton taxa were recorded in the samples. Twenty six out of 70 taxa
recorded in ballast water were totally alien to Western coastal area of Sri Lanka. A
significant (p<0.05) difference was observed in physical and chemical parameters
excluding conductivity and nitrate among four sampling sites. Zooplankton communities
were dominated by Copepod nauplii in all four sites. Alien plankton species observed in
ballast water samples included Peridinium spp., Ceratium declinatum, Ceratium dens,
Rhizosolenia setigera and Prorocentrum spp which are known to be toxic and some of
them are well known for bloom forming.
Findings of this research revealed a greater potential of accidental introduction of alien
planktons to Sri Lankan coastal waters via ballast water. Therefore adoption of ballast
water discharge related regulations and implementation of effective management
measures are important. This study also suggests that the continuous monitoring
programmes in harbours and neighboring coastal area are important in early detection of
new threats arising from plankton introductions.
