As temperature started to affect metamorphosis, the additive effects of temperature and Cu concentration were expected to cause a rapid decrease in metamorphosis as Cu increased. The strength of N-Methylspiperone hydrochloride interaction between SST and Cu was quantified by dividing the observed effect on metamorphosis by the expected additive effect from the modeled data. The interaction plot indicated subadditivity at low temperature-Cu combinations for A. millepora, increasing to additive effects at temperatures less than 31uC and then becoming strongly synergistic at temperatures between 31uC and 33uC and Cu concentrations up to 30 mg l21. The response of A. tenuis was similar; however, there was little apparent sub-additivity and the range of temperature and Cu concentrations where metamorphosis was reduced by 50% more than expected for additivity was broader for this species. Overall, Cu contamination and temperature stress had a stronger synergistic effect in inhibiting metamorphosis of A. tenuis compared to A. millepora, PF-05085727 although the latter species was generally more sensitive to these stressors. Three other studies have examined the combined effects of SST and pollution on adult corals but these used fewer treatment combinations, or a narrower range of treatments, making interactions more difficult to quantify. Nystrom et al. found that the combination of elevated SST and Cu did not interact to affect coral metabolism. Two other studies found that the effect of the herbicides on photosynthesis of coral symbionts decreased as temperature increased from 26 to 30uC, indicative of an antagonistic interaction. Nevertheless, the latter study also showed that two herbicides acted synergistically with higher SSTs as demonstrated by a greater than additive effect on inhibition of symbiont photosynthesis. The current study is the first to demonstrate synergistic effects of environmentally relevant SST and levels of pollution that directly affect corals at a critical phase during their lifehistories. The results from this study demonstrate that the critical early life stages of coral development, during which corals metamorphose from pelagic larvae into sessile polyps, are more sensitive to high SSTs in the presence of the common anthropogenic pollutant copper.