Oxidative damage-dependent on the biotoxin domoic acid exposure in the marine diatom Phaeodactylum tricornutum

Abstract

The biotoxins of toxic algal blooms, like domoic acid (DA), are known to generate several effects on the aquatic trophic chain, specially at higher levels. However, little is known about their effects on non-target organisms such as in the phytoplanktonic community. Some microalgal biotoxins have allelopathic effects on phytoplankton community that could induce changes in the redox balance of target- and non-target organisms. The objective of this work was to analyze the oxidative condition in the diatom Phaeodactylum tricornutum after DA exposure during the algae cycle. The results showed that the superoxide anion (O2􀀀 ) generation rate increased by 5-, 7- and 10-fold in LAG, EXP and STA cells, respectively respect to controls, after 12 min of DA-exposure. The hydrogen peroxide (H2O2) content was also significantly increased (158, 312 and 103 % in the LAG, EXP and STA cells, respectively). The redox balance in the hydrophilic medium reached the highest values after 12 min of DAexposure, as compared to controls (0.48 ± 0.05, 3.2 ± 0.4, 2.2 ± 0.3 in the LAG, EXP and STA cells, respectively). In the lipophilic media the balance was significantly altered in the STA and EXP algae reaching values of 0.21 ± 0.04 and 0.29 ± 0.01, respectively. Even though the antioxidant capacity was increased after 12 min of DA-exposure, as compared to controls (1.8-, 1.7- and 1.4-fold in LAG, EXP and STA cells, respectively), this protection did not prevent the observed protein and lipidic damage. These results suggest that DA-exposure of this non-target algae generates changes in their oxidative balance and cellular damage during the growth cycle, emphasizing the importance of the biotoxin presence in the aquatic community. These effects may lead to alterations at the economic, ecological, physiological, and biochemical levels, intensifying the risk to marine wildlife.