Effects of daily temperature range (DTR) and thermal priming on acquired thermal resistance in Porites species in Moorea, French Polynesia
摘要
Thermal priming through exposure to a daily temperature range (DTR) has been proposed as a mechanism by which corals can acclimatize to elevated temperature. This study tested the effects of DTR on the response of corals from the shallow (3-m depth) backreef of Moorea, French Polynesia, to elevated temperature, and compared corals from two sites representing low-DTR (0.618 °C annually) and high-DTR (0.991 °C annually). Fragments of Porites rus were reciprocally transplanted between these sites for 14 days to evaluate the effect of local environmental conditions (other than DTR) on coral phenotype. The null outcome of this experiment on maximum photochemical efficiency of open RCIIs (Fv/Fm) and growth rate suggested that environmental conditions other than DTR did not affect these corals. In April/May 2023, fragments of P. rus from the low- and high- DTR sites were used to test for the effect of DTR on Fv/Fm and growth rate in response to exposure to 28.7 °C versus 31.8 °C over 14 days; Fv/Fm was depressed at 31.8 °C but was unaffected by DTR. This experiment was repeated in August 2023 using P. rus and massive Porites from the same sites and exposed to 26.7 °C versus 29.9 °C over 14 days. For massive Porites, Fv/Fm was unaffected by high temperature in corals from the high-DTR site but was reduced by 5% in corals from the low-DTR site; for P. rus, Fv/Fm was also reduced by 5–8% in corals from the both the low- and high-DTR sites. Growth was unaffected by DTR in both experiments. Together, these results suggest that it is unlikely that the natural DTR in Moorea confers physiological benefits for corals exposed to 30–32 °C.