Effects of Aromatic Hydrocarbons and Marine Sediments from Niger Delta on the Growth of Microalga Phaeodactylum tricornutum

Aims: To determine effects of aromatic hydrocarbons and marine sediments from Niger Delta on the growth of microalga Phaeodactylum tricornutum.

Study Design: Fifteen treatments and the control were designed in triplicates in which long cells containing 25 mL of the algae-toxicant dilutions were supplemented with 0.0 mg /L, 1.0 mg /L, 1.8 mg /L, 3.2 mg /L, 5.6 mg /L, and 18.0 mg /L of xylene, anthracene and pyrene each; three sediments and potassium dichromate incubated for 3 days at 20 ± 2°C. The fifteen treatments and control (K2Cr2O7) designated as C0, C1, C2, C3, C4 and C5 were used to determine their median effective concentration (ErC50) on the growth of microalga Phaeodactylum tricornutum.

Place and Duration of Study: Department of Microbiology, Chukwuemeka Odumegwu Ojukwu University, Uli Nigeria between February, 2018 and July, 2018.

Methodology: A laboratory scale study was carried on the sediment samples from the three studied areas using physiochemical analysis and marine microalga toxicity test.

Results: The findings revealed that the three sampling sites contain higher quantities of aromatic hydrocarbons, heavy metals and other physio-chemical parameters in the sediment samples than water samples. The K2Cr2O7had the highest ErC50 value of 08.07 ± 0.03 mg /L with CV and r2 values of 68.61% and 0.99 while pyrene in Nembe sediment had the least ErC50 value of 04.63 ± 0.01 mg /L with CV and r2 values of 78.27% and 0.98 with very strong significant positive linear relationship between algal number and sample concentrations (P = .05).

Conclusion: Thus, the toxicity results (> 1 mg /L <EC50 ≤ 10 mg /L) in this study are in line with other toxicity values for this type of toxicants, and are therefore considered to be scientifically relevant in ecotoxicological risk assessment of Niger Delta, Nigeria.