Domoic Acid Oxidative Effects on the Microalgae Phaeodactylum tricornutum

Area of Science:

• Marine Biology
• Ecotoxicology
• Phytoplankton Physiology

Background:

• Domoic acid (DA) is a marine biotoxin known to induce oxidative stress in animals.
• The effects of DA on phytoplankton, crucial primary producers, are less understood.
• Investigating DA's impact on diatoms is vital for understanding marine ecosystem health.

Purpose of the Study:

• To determine if DA exposure generates reactive oxygen species (ROS) in the marine diatom *Phaeodactylum tricornutum*.
• To assess modifications in the intracellular antioxidant capacity of diatoms under DA exposure.
• To evaluate DA's effects across different growth phases of the diatom.

Main Methods:

• Exposure of *Phaeodactylum tricornutum* to 64 µM DA across exponential, latent, and stationary growth phases.
• Measurement of intracellular ROS production using 2',7' dichlorofluorescein diacetate dye.
• Assay of antioxidant enzyme activities (superoxide dismutase, catalase, glutathione-related enzymes).
• Quantification of non-enzymatic antioxidants (glutathione, ascorbate).

Main Results:

• DA exposure led to a seven-fold increase in ROS production in exponentially growing cells.
• Activities of superoxide dismutase, catalase, and glutathione-related enzymes significantly increased.
• Cellular glutathione and ascorbate contents significantly decreased after DA treatment.
• Similar oxidative stress patterns were observed in latent and stationary growth phases.

Conclusions:

• Domoic acid induces significant oxidative stress in the marine diatom *Phaeodactylum tricornutum*.
• DA exposure alters the intracellular antioxidant system, increasing ROS generation and enzyme activity while depleting key antioxidants.
• These findings highlight a potential oxidant-dependent impact of DA on non-toxic algae, with implications for marine food webs.