Declining health of scleractinian corals in response to deteriorating environmental conditions is widely acknowledged, however links between physiological and functional genomic responses of corals are less well understood. Here we explore growth and the expression of 20 target genes with putative roles in metabolism and calcification in the branching coral, Acropora millepora, in two separate experiments: 1) elevated pCO2 (464, 822, 1187 and 1638 $μ$atm) and ambient temperature (27 °C), and 2) elevated pCO2 (490 and 822 $μ$atm) and temperature (28 and 31 °C).
Anthropogenic CO2 is causing warming and ocean acidification. Coral reefs are being severely impacted, yet confusion lingers regarding how reefs will respond to these stressors over this century. Since the 1982-83 El Niño-Southern Oscillation warming event, the persistence of reefs around the Galápagos Islands has differed across an acidification gradient. Reefs disappeared where pH \textless 8.0 and aragonite saturation state ($Ømega$arag) ≤ 3 and have not recovered, whereas one reef has persisted where pH \textgreater 8.0 and $Ømega$arag \textgreater 3.
Ocean acidification driven by rising levels of CO2 impairs calcification, threatening coral reef growth. Predicting how corals respond to CO2 requires a better understanding of how calcification is controlled. Here we show how spatial variations in the pH of the internal calcifying fluid (pHcf) in coral (Stylophora pistillata) colonies correlates with differential sensitivity of calcification to acidification. Coral apexes had the highest pHcf and experienced the smallest changes in pHcf in response to acidification.
As global ocean change progresses, reef-building corals and their early life history stages will rely on physiological plasticity to tolerate new environmental conditions. Larvae from brooding coral species contain algal symbionts upon release, which assist with the energy requirements of dispersal and metamorphosis. Global ocean change threatens the success of larval dispersal and settlement by challenging the performance of the larvae and of the symbiosis.
The physiological response to individual and combined stressors of elevated temperature and pCO2 were measured over a 24-day period in four Pacific corals and their respective symbionts (Acropora millepora/Symbiodinium C21a, Pocillopora damicornis/Symbiodinium C1c-d-t, Montipora monasteriata/Symbiodinium C15, and Turbinaria reniformis/Symbiodinium trenchii). Multivariate analyses indicated that elevated temperature played a greater role in altering physiological response, with the greatest degree of change occurring within M. monasteriata and T. reniformis.