Acidic environment and the mixture of crude oil and dispersant not causing synergistic toxicity to Litopenaeus vannamei

Oil spill events could have devastating effects on the environment and the application of dispersants could have more adverse impact on the affected organisms. Meanwhile, the decreasing ocean pH could have synergistic toxicity effects on marine organisms. This study aimed to examine the short-term toxicity effect of chemically enhanced water accommodated fractions (CEWAFs) to Litopenaeus vannamei and to figure out the synergistic toxicity effect of CEWAFs with pH 6.5 and 8.5. Healthy post larvae L. vannamei were exposed to CEWAFs with concentrations of 0%, 3%, 6%, 12% and 24% under the pH concentration of 6.5 and 8.5 for 72 hours to quantity their mortality. The LC₅₀ was performed using probit analysis while the PAHs of the CEWAFs were analyzed using gas chromatography method. Results showed that anthracene constituted a half of PAHs while the 72-h LC₅₀ of CEWAFs at pH 6.5 and 8.5 was 8.695±1.66 mL L^-1 9.29±0.4 mL L^-1 respectively categorized as practically non-toxic. Furthermore, the mixture of dispersant and WAFs did not cause a synergistic toxicity effect. The univariate statistical analysis also confirmed that there was no synergistic toxicity of CEWAFs with pH 6.5 and 8.5 to the whiteleg shrimps, L. vannamei.