Coral reefs are declining worldwide due to a combination of global and local stressors. Multiple stressors can have synergistic (increased stress) or antagonistic effects (decreased stress). For example, nutrient pollution and thermal stress have been shown to produce synergistic effects in corals, exacerbating the physiological damage. Conversely, mild heat stress has been shown to prepare corals to better cope with the same or other types of environmental stress. To examine the interaction between land-based sources of pollution and thermal stress, acute heat stress experiments were conducted on Acropora hyacinthus from five sites around Tutuila, American Samoa with differing pollution impact. Bleaching responses were measured visually, using photographic assessment to estimate chlorophyll content, and through measuring photosynthetic efficiency. Endosymbiont communities were assessed at each site using quantitative PCR. RNA sequencing was used to compare differences among genes regulated during heat stress. Preliminary results show differences in symbiont communities among sites, with heat tolerant Durusdinium dominating in areas with higher pollution impact and heat sensitive Cladocopium more common in pristine areas. Pollution stress may induce a shift towards Durusdinium thereby enhancing resistance to subsequent heat stress in the near term. RNAseq data showed more differentially expressed genes during heat stress in the high pollution site, with fewer differentially expressed genes in the medium pollution site and fewest in the low pollution site. We present potential mechanisms underlying coral thermal tolerance in pollution-impacted areas. Our results highlight the importance of identifying heat tolerant corals in “non-pristine” areas and their potential to seed nearby reefs following bleaching events.