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ABSTRACT
The study on the phytotoxicity of ballast water on two microalgae was carried out within a period of 14 days in a laboratory. Two microalgae Volvox aureus and Volvox globator were used. The experiment was carried out with concentrations of 0%, 1%, 5%, 10%, 15%, 20% and 25% of ballast water. The growth responses of the microalgae and their different concentrations were measured using a spectrophotometer at a wavelength of 750nm. Samples were also analyzed every two days for some physical and chemical parameters. Descriptive statistics, inferential; One-way analysis of variance (ANOVA), repeated measure paired t-test and Turkey test were done using Microsoft Excel 2010 and SPSS 20. It was observed for Volvox aureus that growth was recorded only in concentrations 1% and 20% on days 2 and 8 and while for Volvox globator, growth was recorded on days 8 and 10 for concentrations 0% (control) and 5%. The percentage inhibition was equally very high for both microalgae in their 15% concentration respectively. The temperature for Volvox aureus was within the optimum range of 20OC and 30OC on days 2 to 4 and 10 through 12, this could possibly be the reason for the growth recorded above and this was same for Volvox globator. The Dissolved Oxygen value for both microalgae was relatively low; another reason for the their inhibitory growth. The turbidity level also grew towards the end days of the experiment, this also is another reason for their inhibitory growth as turbidity shields sun light from reaching indwelling plants for photosynthesis. The conductivity as well as the Chemical Oxygen Demand were also analyzed and found to fairly increase towards the end days of the experiment. The result proved that ballast water is inhibitory to the growth of the sample microalgae as a result of the above stated factors and more-so, the phytotoxicity of other organisms in the ballast water.
