Climate stressors have reduced coral cover worldwide prompting an upscale in coral restoration efforts, particularly in Florida. Outplanting stressor-resistant coral genotypes could enhance resilience within restored populations. Disease-resistant Acropora cervicornis in Florida possess diverse microbiomes with low abundances of the intracellular parasite Aquarickettsia (low-Aquarickettsia), whereas disease susceptible corals are dominated by the parasite (high-Aquarickettsia). We examined the microbial communities of low-Aquarickettsia and high-Aquarickettsia A. cervicornis genotypes after a two month exposure to climate change scenarios: control ambient conditions, ocean warming, ocean acidification and these stressors combined. Additionally, a suite of coral host physiological responses were measured. Bacterial communities of high-Aquarickettsia within the ocean warming and combined treatments significantly differed from control and ocean acidification treatments with a greater abundance of Campylobacterales under climate change treatments. Aquarickettsia increased within resistant corals under high temperature and combined treatments. Low-Aquarickettsia genets had a greater reduction in maximum electron transport rate within the algal symbionts compared with high-Aquarickettsia genets, which became significant under climate change scenarios indicating a potential tradeoff. Our results suggest that climate change may have a greater influence on the microbiomes of high-Aquarickettsia corals, but increased temperatures may allow the proliferation of Aquarickettsia within resistant corals, resulting in the loss of disease resistant traits, and result in physiological tradeoffs.
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