Lipid profiling of symbiosomes in scleractinian coral in response to herbicide-induced photoinhibition

Abstract

Photosystem II herbicides, such as Irgarol 1051, are frequently found as common contaminants in coral reefs and represent a particular threat to coral health due to the effect of photoinhibition on symbiotic algae. Membrane lipids form dynamic structures depending on cell requirements, offering a distinct lipid profile for characterizing ambient condition-induced cellular alterations. To obtain fundamental insight into the effect of herbicides on coral health, the glycerophosphocholine profiles of symbiosomes in a coral, Seriatopora caliendrum, were observed during 4 days of Irgarol exposure (50–200 ng/L). On day 1 of exposure, the predominant changes were an increase in phosphatidylcholines with 2 unsaturated chains, especially PC(22:6/22:6), a saturated plasmanylcholine PC(O-18:0/16:0) and a decrease in polyunsaturated plasmanylcholines. These changes indicated an upregulation of membrane-related functions to cope with physiological disturbances, such as increased H2O2 levels, induced by photoinhibition. However, these changes were mostly inverted or insignificant after day 1of exposure. A decrease in lyso-glycerophosphocholines and an increase in phosphatidylcholines with a polyunsaturated chain were also induced as the exposure time increased. Based on the physicochemical properties, these lipid changes can be considered to counteract lipid oxidation-induced perturbations in membrane structure and to protect against oxidative attack. In addition, the effect of fat-soluble antioxidants on lipid peroxidation was observed in the high-dose (200 ng/L)-treated group, resulting in a change in the lipid profile disproportionate to the dose. This study concludes that coral accommodates the membrane lipid profile of symbiosomes to herbicide-induced photoinhibition dependent on the duration of exposure.