Insights into Cellular Localization and Environmental Influences on the Toxicity of Marine Fish-Killing Flagellate, Heterosigma akashiwo

Heterosigma akashiwo is a unicellular microalga which can cause massive mortality in both wild and cultivated fish worldwide, resulting in substantial economic losses. Environmental parameters such as salinity, light, and temperature showed a significant effect on bloom initiation and the toxicity of H. akashiwo. While in previous studies a one-factor-at-a-time (OFAT) approach was utilized, which only changes one variable at a time while keeping others constant, in the current study a more precise and effective design of experiment (DOE) approach, was used to investigate the simultaneous effect of three factors and their interactions. The study employed a central composite design (CCD) to investigate the effect of salinity, light intensity, and temperature on the toxicity, lipid, and protein production of H. akashiwo. A yeast cell assay was developed to assess toxicity, which offers rapid and convenient cytotoxicity measurements using a lower volume of samples compared to conventional methods using the whole organism. The obtained results showed that the optimum condition for toxicity of H. akashiwo was 25 & DEG;C, a salinity of 17.5, and a light intensity of 250 & mu;mol photons m(-2) s(-1). The highest amount of lipid and protein was found at 25 & DEG;C, a salinity of 30, and a light intensity of 250 & mu;mol photons m(-2) s(-1). Consequently, the combination of warm water mixing with lower salinity river input has the potential to enhance H. akashiwo toxicity, which aligns with environmental reports that establish a correlation between warm summers and extensive runoff conditions that indicate the greatest concern for aquaculture facilities.

Automated summary

The study used a central composite design to investigate the effect of salinity, light intensity, and temperature on the toxicity, lipid, and protein production of H. akashiwo. The optimum conditions for toxicity, lipid production, and protein production were found to be 25°C temperature, 17.5 salinity, and 250 μmol photons m(-2) s(-1) light intensity. The combination of warm water and lower salinity can potentially enhance the toxicity of H. akashiwo, which is of great concern for aquaculture facilities.