Antioxidant responses in the mussels perna viridis exposed to chattonella marina

The red tide organism Chattonella marina (Raphidophyceae) has been associated with fish kills, leading to serious economic losses and posing a significant ecological risk to marine biota. The precise toxic actions of these algae remain unclear, but there is growing scientific evidence to suggest that production of reactive oxygen species (ROS) may be the main cause of mortality. In this study, we investigated the production of hydrogen peroxide (H2O2) by C. marina. Subsequently, we examined the antioxidant responses as well as lipid peroxidation in gills and hepatopancreas of the mussel Perna viridis upon exposure to C. marina at sublethal concentrations (l0³ and 9 x 10³ cells/ml). Despite the extracellular levels of H2O2 generated were up to 20 μM (at 10³ cells/ml) and 50 μM (at 9 x 10³ cells/ml) [which were about 8 and 20 folds higher than those measured in a non-toxic algal (Dunaliella tertiolecta) and seawater controls], no significant differences could be observed in all examined biochemical parameters (i.e. SOD, CAT, GPx, GST, GR, GSH, LPO and ATPase) in mussels between treatment and control groups. In another experiment, mussels were exposed to H2O2 and neither antioxidant responses nor lipid peroxidation were induced even the concentration reached up to 0.5 rnM (which was 10-fold higher than those generated by C. marina cultured under optimal laboratory conditions). These data collectively indicate that the production of H2O2 by C. marina is not high enough to elicit antioxidant responses in mussels, let alone causing significant damages and mortality. As such ROS is unlikely to be an important toxicological mechanism of the flagellate. We conclude that none of the selected antioxidant responses in mussels can be used as biomarkers for oxidative stress induced by harmful algae.

Author: Kwok, Chung Ting

Source: City University of Hong Kong

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