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<p>Coral reefs are increasingly threatened by ocean warming. Interestingly, corals from hypersaline environments such as the Gulf of Aqaba&#xa0;(GoA) show high thermotolerance. To test whether salinity modulates coral thermal tolerance, we exposed <i>Stylophora pistillata</i> from the hypersaline Gulf of Aqaba and <i>Montipora digitata</i> from Bali, Indonesia to a simulated heatwave (1&#xa0;°C rise every four days) lasting 39&#xa0;days under ambient (35&#xa0;PSU) and elevated (42&#xa0;PSU) salinity. Elevated temperature significantly affected PSII yield of <i>S. pistillata</i>, with a more pronounced decrease at 35 PSU (9.0%) as compared to 42 PSU (3.4%) between 32.1 and 33.8&#xa0;°C. Similarly, loss of chlorophyll <i>a</i> fluorescence in <i>S. pistillata</i> was significantly alleviated by hypersalinity at 34.1&#xa0;°C (94.8 versus 67.6% loss at 35 and 42&#xa0;PSU, respectively). However, symbiont loss in <i>S. pistillata</i> was not modulated by elevated salinity, with a significant overall decline of 68% at 34.1&#xa0;°C. In contrast, <i>M. digitata</i> exhibited significantly accelerated mortality under hypersalinity during the heatwave, with no survival at 32.2&#xa0;°C and 33.3&#xa0;°C at 42 and 35&#xa0;PSU, respectively. Finally, photosystem II in <i>M. digitata</i> was significantly inhibited at 42 PSU only (6.8–18.9% decline at ≥ 31.3&#xa0;°C). This suggests that contrary to <i>S. pistillata</i>, hypersaline conditions exacerbated thermal stress in <i>M. digitata</i>. Our results suggest a limited role for hypersalinity in enhancing coral thermotolerance. The evolutionary history of coral populations may be a more important determining factor, although future experiments involving more species from the GoA region should verify this.</p>

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Contrasting effects of elevated salinity on thermotolerance of Stylophora pistillata and Montipora digitata

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月7日

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  • Tim Wijgerde,
  • Michael Yeboah,
  • Thomas van de Grootevheen,
  • Tom Roebbers,
  • Rick Verkooijen,
  • Rosa van der Ven,
  • Ronald Osinga

摘要

Coral reefs are increasingly threatened by ocean warming. Interestingly, corals from hypersaline environments such as the Gulf of Aqaba (GoA) show high thermotolerance. To test whether salinity modulates coral thermal tolerance, we exposed Stylophora pistillata from the hypersaline Gulf of Aqaba and Montipora digitata from Bali, Indonesia to a simulated heatwave (1 °C rise every four days) lasting 39 days under ambient (35 PSU) and elevated (42 PSU) salinity. Elevated temperature significantly affected PSII yield of S. pistillata, with a more pronounced decrease at 35 PSU (9.0%) as compared to 42 PSU (3.4%) between 32.1 and 33.8 °C. Similarly, loss of chlorophyll a fluorescence in S. pistillata was significantly alleviated by hypersalinity at 34.1 °C (94.8 versus 67.6% loss at 35 and 42 PSU, respectively). However, symbiont loss in S. pistillata was not modulated by elevated salinity, with a significant overall decline of 68% at 34.1 °C. In contrast, M. digitata exhibited significantly accelerated mortality under hypersalinity during the heatwave, with no survival at 32.2 °C and 33.3 °C at 42 and 35 PSU, respectively. Finally, photosystem II in M. digitata was significantly inhibited at 42 PSU only (6.8–18.9% decline at ≥ 31.3 °C). This suggests that contrary to S. pistillata, hypersaline conditions exacerbated thermal stress in M. digitata. Our results suggest a limited role for hypersalinity in enhancing coral thermotolerance. The evolutionary history of coral populations may be a more important determining factor, although future experiments involving more species from the GoA region should verify this.