The Ecophysiological Responses Of Common Phytoplankton To Typical Pollutants In Pearl River Estuary

Heavy metals and persistent organic pollutants are common in the marine environment. Three kinds of heavy metal:copper, cadmium and zinc, two kinds of persistent organic pollutants:polycyclic aromatic hydrocarbons and polychlorinated biphenyls were selected in this study as pollutants, and three common marine phytoplankton species from Pearl River Estuary: Scrippsiella trochoidea, Skeletonema tropicum and Heterosigma akashiwo as test organisms.Based on the results, the copper, zinc, cadmium, polycyclic aromatic hydrocarbons and polychlorinated biphenyls showed a good dose-response relationship on the toxicity of the three microalgae. The exposure concentrations were positively correlated with the inhibition rate gradually. The 96h EC50 of Zinc on the three red-tide algae were 1.452 mg·L-1,0.897 mg·L-1 and 2.402mg·L-1, Copper were 0.410 mg·L-1,0.153 mg·L-1 and 0.695 mg·L-1, and Cadmium were 2.832 mg·L-1, 1.004 mg·L-1 and 2.417 mg·L-1, respectively. Skeletonema tropicum was most sensitive to the heavy metals, tolerance was the worst. Among the heavy metals, copper was the most toxic one. The 96h EC50 of Polycyclic aromatic hydrocarbons on three microalgae were 0.052 mg·L-1,0.210 mg·L-1 and 0.062mg·L-1, respectively. Polycyclic aromatic hydrocarbons was most toxic to Scrippsiella trochoidea, followed by Heterosigma akashiwo and Skeletonema tropicum. The 96h EC50 of PCBs on three harmful algae were 0.103 mg·L-1,0.009 mg·L-1 and 0.023mg·L-1, respectively. PCBs was the most toxic to Skeletonema tropicum, followed by Heterosigma akashiwo and Scrippsiella trochoidea.The safety threshold of Copper to three species of microalgae were 0.041 mg·L-1 0.015 mg·L-1 and 0.070 mg·L-1, respectively. Whereas the threshold of Zinc were 0.145 mg·L-1,0.090 mg·L-1 and 0.240 mg·L-1, respectively. In the Pearl River Estuary, refer to the in situ monitoring data, concentrations of Copper and Zinc were not toxic to Scrippsiella trochoidea and Heterosigma akashiwo. The safety threshold of Cadmium to three species of algae were 0.283 mg·L-1,0.100 mg·L-1 and 0.242 mg·L-1, respectively. Referring to the in situ monitoring data, These concentrations were safe to the three microalgae. The safety threshold of polycyclic aromatic hydrocarbons to three microalgae were 0.005 mg·L-1,0.021 mg·L-1 and 0.006 mg·L-1, while the PCBs were 0.010 mg·L-1,0.001 mg·L-1 and 0.002mg·L-1, respectively, both were with the high toxicity.At low concentrations of heavy metals and persistent organic pollutant exposure, the algal cells can work against the toxic effects of pollutants by activating antioxidant enzymes. But when the pollutants' concentrations exceeded to a certain range, the antioxidant activity of the enzymes would be decreased, even inhibited, indicating that SOD, CAT only work in a certain concentration range.