Abstract
Phenanthrene is one of the most abundant polycyclic aromatic hydrocarbons (PAHs) found in continental shelf environment of China and is on the EPA’s Priority Pollutant list. In this study, the effects of phenanthrene on marine algal growth rate were determined after 96-h exposure at pH 6.0, 7.0, 8.0, 9.0, and 10.0 in seawater of salinity 35. Two measuring techniques to assess growth inhibition were also compared using prompt fluorescence and microscopic cell count. The results showed that the toxicity of phenanthrene increased significantly (p < 0.05) with decreasing pH, with the nominal concentration required to inhibit growth rate by 50%, EC50, decreasing from 1.893 to 0.237 mg L−1 as pH decreased from 9.0 to 6.0, with a decrease higher than 55% from 10.0 to 9.0. In addition, the nominal EC50 values calculated in this study were at the same range of some environmental concentrations of phenanthrene close to areas of crude oil exploration. Based on the two measuring techniques, the results showed that cell count and fluorescence measurement were significantly different (p < 0.05), and the nominal EC50 values calculated with cell count measurement were significantly higher than fluorescence measurement at pH 8.0, 9.0 and 10.0. In conclusion, the present studies confirmed that acidification of seawater could affect the toxicity of phenanthrene to this species of microalgae, and which encouraged further studies involving responses of marine organisms to ocean acidification.
Highlights
Polycyclic aromatic hydrocarbon (PAHs) are a class of complex organic chemicals with two or more fused aromatic rings, which are known to be priority pollutants in the environment and can be transported to the globe from riverine runoff and long range atmospheric transport[1,2], with the majority of inputs arising from anthropogenic sources[3]
Prior to testing the effect of pH on the acute toxicity of phenanthrene, growth of Chlorella salina was assessed under the stated test conditions
The slowest growth rate was observed for pH 6.0, and the highest growth rates were observed at pH 9.0 and pH 10.0 closely followed by pH 8.0 and pH 7.0
Summary
Polycyclic aromatic hydrocarbon (PAHs) are a class of complex organic chemicals with two or more fused aromatic rings, which are known to be priority pollutants in the environment and can be transported to the globe from riverine runoff and long range atmospheric transport[1,2], with the majority of inputs arising from anthropogenic sources (e.g., fossil fuel and combustion)[3]. A variety of responses of living things and their environment to OA have been studied across a global range, such as effects on organisms13,changes in toxicity[14] and behavior of substances[15]. As previous studies have shown, pH plays an important role in affecting the toxicity of chemical pollutants to organisms. This is explained by the fact that pH may change seawater chemistry in several different ways, first is the chemical equilibrium with carbonic acid, the chemical status of heavy metals, and the characteristics of dissolved substances[17]. We performed growth inhibition tests with phenanthrene as reference chemical and with a tropical marine green algae according to OECD33. A secondary objective was to compare the difference of two measuring techniques in growth inhibition tests
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