Effects of salinity, pH and temperature on the re-establishment of bioluminescence and copper or SDS toxicity in the marine dinoflagellate Pyrocystis lunula using bioluminescence as an endpoint

Pyrocystis lunula is a unicellular, marine, photoautotrophic, bioluminescent dinoflagellate. This organism is used in the Lumitox® bioassay with inhibition of bioluminescence re-establishment as the endpoint. Experiments determined if acute changes in pH, salinity, or temperature had an effect on the organisms’ ability to re-establish bioluminescence, or on the bioassayʹs potential to detect sodium dodecyl sulfate (SDS) and copper toxicity. The re-establishment of bioluminescence itself was not very sensitive to changes in pH within the pH 6-10 range, though reducing pH from 8 to levels below 6 decreased this capacity. Increasing the pH had little effect on Cu or SDS toxicity, but decreasing the pH below 7 virtually eliminated the toxicity of either compound in the bioassay. Lowering the salinity from 33 to 27‰ or less resulted in a substantial decrease in re-establishment of bioluminescence, while increasing the salinity to 43 or 48 ‰ resulted in a small decline. Salinity had little influence on the bioassayʹs quantification of Cu toxicity, while the data showed a weak negative relationship between SDS toxicity and salinity. Reestablishment of bioluminescence showed a direct dependence on temperature, but only at 10 °C did temperature have an obvious effect on the toxicity of Cu in this bioassay.