Seasonal dynamics of fatty acid biomarkers in the soft coral Sinularia flexibilis, a common species of Indo-Pacific coral reefs

Abstract

Year-round fluctuation in environmental conditions have a considerable influence on the level of biomarkers, that are usually applied for monitoring marine invertebrates. To date, no data on annual cycles of fatty acid (FA) biomarkers in tropical soft corals are available. The FA composition of the alcyonarian Sinularia flexibilis containing symbiotic microalgae was studied during a year. Two major FAs, 20:4n-6 and 16:0, determined the level of polyunsaturated and saturated FAs (PUFAs and SFAs). The insignificant variations in PUFA content indicated a relatively stable level of phospholipids that formed the structural base of coral cell biomembranes. No clear relationship between the PUFA markers of photosynthetic symbionts and the solar radiation was found. The three-fold increase in the SFA level in the summer correlated with the water temperature and indicated a rise in the level of neutral lipids that made up the energy reserve of corals. The seasonal changes in FA biosynthesis, membrane fluidity, and coral nutrition are discussed.