Influence of seasonal and latitudinal temperature variation on early life-history traits of a coral reef fish

Temporal and latitudinal gradients in ocean temperature may be useful for predicting the likely responses of marine species to accelerating global warming. Here, we examined seasonal variations in early life-history traits of the reef fish Pomacentrus moluccensis at Lizard Island on the Great Barrier Reef (GBR). Latitudinal variations were then compared among three locations from Kimbe Bay in Papua New Guinea to the southern GBR (18° latitude). At Lizard Island, a 4°C temperature rise from spring to summer was correlated with a 0.13 mm day-1 increase in pre-settlement growth rates and a 3.28-day decrease in pelagic larval duration (PLD). The latitudinal comparison revealed a non-linear relationship where growth rate and settlement size declined and PLD increased at Kimbe Bay where temperature was the highest of all the study sites. Furthermore, the slopes of latitudinal variations in life-history traits as a function of temperature within the GBR were significantly steeper than those in the temporal analysis. These latitudinal patterns were likely to be shaped by (1) the species thermal reaction norm, (2) local adaptation or (3) location-specific environmental and demographic characteristics. The significant correlations of early life-history traits with natural temperature gradients emphasise the potential sensitivity of reef fish larvae to global warming.