The influence of salinity on metal toxicity to the marine microalga, Phaeocystis antarctica

• Main Author: Whitelaw, Nicholas
• Format: Text
• Language: unknown
• Published: School of Earth and Environmental Sciences & School of Chemistry 2016
• Subjects: metal toxicity; ice melting; salinity; phytoplankton; microalgae; Antarctica; Antarctic; The Antarctic; Antarc*; Sea ice
• Online Access: https://ro.uow.edu.au/thsci/179; https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1179&context=thsci

The growth and retreat of Antarctic sea ice is one of the world’s most significant large-scale annual changes, resulting in a highly fluctuating, dynamic environment. Organisms are subjected to large annual and diurnal fluctuations in seawater properties. Variations in salinity are known to have a prominent effect on the growth of marine phytoplankton that is an important food source for higher order organisms. Contamination is present in the Antarctic marine environment from past anthropogenic activities. Metal contaminants have different speciation schemes in seawater and are known to have toxic effects on phytoplankton, with unknown consequences at the population scale. Phaeocystis antarctica, a marine, unicellular, eukaryotic Prymnesiophyte, was chosen for this study to apply a 10-d laboratory toxicity bioassay to investigate the effect of Cu, Cd, Pb, Zn and Ni in single metal and metal mixture exposures at varying salinities. Flow cytometry was used successfully to determine the growth rate inhibition due to the presence of metals. Analyses of cellular parameters, including chlorophyll a fluorescence, cell size, internal granularity, and membrane permeability were also performed using flow cytometry. Lead and cadmium caused greater growth rate inhibition to Phaeocystis antarctica with decreasing salinity. Metal mixture exposures containing Cu, Cd, Pb, Zn and Ni were less toxic at lower salinities than single metal treatments of Cd and Pb at the same salinity and concentration. Findings in this study concur with previous studies which showed that single metal toxicity is not predictive of metal mixture toxicity. Further investigation into the toxic modes of action at the intracellular level is required to determine where the metals singly and in metal mixtures are exerting their toxicity and the extent to which it occurs in P. antarctica. The findings of this study can be used to inform environmental risk management for contaminated site remediation, and to identify risks under future climate change scenarios.