Temporal and spatial variation in fatty acid composition in Acropora tenuis corals along water quality gradients on the Great Barrier Reef, Australia

Fatty acids (FA) play a vital role in coral physiology, metabolism and stress resistance. Optimal health requires a balance of fatty acids, and more specifically essential polyunsaturated fatty acids (PUFA), for efficient biochemical and physiological functioning. Therefore, it is necessary to fully assess and evaluate the viability of FA as biomarkers for monitoring the health of coral populations. This study explores seasonal and spatial variation in the abundance of 17 FA in the coral Acropora tenuis, along two water quality gradients on the central Great Barrier Reef. Ratios of key FA varied similarly along the two water quality gradients and were highest in corals from comparatively good water quality conditions. Strong differences in PUFA composition were found between wet and dry seasons, with high percentage n-3 PUFA defining the dry seasons (June 2013 and October 2013) and high percentage n-6 PUFA defining the wet seasons (February 2013 and 2014). Saturated FA and monounsaturated FA concentrations varied with season, positively correlated with Symbiodinium density, and had highest concentrations in corals exposed to relatively poor water quality. Overall, results demonstrate that essential FA and their derived ratios support FA as a potential indicator of coral holobiont health; however, strong seasonal variation may negate FA and their derived ratios as water quality indicators.