High nutrient concentrations as well as elevated temperature above summer mean monthly maximums have significant negative impacts on the physiology of the coral holobiont. However, moderate nutrient concentrations (< 6 μmol L−1 NO3− and 0.40 μmol L PO43−) have been shown to have a positive effect on coral and endosymbiont physiology and to minimize or mitigate the negative effects of summertime elevated temperature. As the oceans continue to warm, corals will face elevated temperatures in winter as well as summer. Yet, few studies have assessed the potential impacts of increases in winter temperature on corals and none have evaluated the possible mitigating or exacerbating effect of nutrients during warmer winters of the future. Here, we tested the effects of elevated temperature and moderate nutrients for 22 days during the winter on Montipora monasteriata, Acropora muricata, and Pocillopora damicornis in a fully factorial experiment with two seawater temperatures (average winter temperature and projected winter temperature later this century of + 4 °C) and two nutrient levels (ambient nutrients and moderate nutrients of + 4.0 μmol L−1 NO3− and + 0.20 μmol L−1 PO4−3). Coral tissue δ15N composition indicated that the added nitrate was taken up by the algal endosymbionts and transferred to the coral host in all three species under both temperature regimes. All three species significantly differed in their physiological profiles (chlorophyll a, protein, lipids, carbohydrates, biomass, and δ13Ch-e) and had species-specific physiological responses to the individual and synergistic effects of increased wintertime temperatures and moderate nutrients. Montipora monasteriata and A. muricata increased one or more energy reserves in response to the individual effects of moderate nutrients or increased temperatures. Pocillopora damicornis shifted their trophic status toward greater photoautotrophy under the combined effects of moderate nutrients and increased temperatures. Overall, our results indicate an overall net positive species-specific physiological responses to the individual and combined effects of moderate nutrients and increased winter temperatures.

Moderate nutrients and future warmer wintertime temperatures have a net positive effect on the physiology of three species of coral from the southern Great Barrier Reef

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2026年3月20日

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Stephen Levas,
Nicole Price,
Kenneth Anthony,
Andréa Grottoli

摘要

High nutrient concentrations as well as elevated temperature above summer mean monthly maximums have significant negative impacts on the physiology of the coral holobiont. However, moderate nutrient concentrations (< 6 μmol L⁻¹ NO₃⁻ and 0.40 μmol L PO₄³⁻) have been shown to have a positive effect on coral and endosymbiont physiology and to minimize or mitigate the negative effects of summertime elevated temperature. As the oceans continue to warm, corals will face elevated temperatures in winter as well as summer. Yet, few studies have assessed the potential impacts of increases in winter temperature on corals and none have evaluated the possible mitigating or exacerbating effect of nutrients during warmer winters of the future. Here, we tested the effects of elevated temperature and moderate nutrients for 22 days during the winter on Montipora monasteriata, Acropora muricata, and Pocillopora damicornis in a fully factorial experiment with two seawater temperatures (average winter temperature and projected winter temperature later this century of + 4 °C) and two nutrient levels (ambient nutrients and moderate nutrients of + 4.0 μmol L⁻¹ NO₃⁻ and + 0.20 μmol L⁻¹ PO₄⁻³). Coral tissue δ¹⁵N composition indicated that the added nitrate was taken up by the algal endosymbionts and transferred to the coral host in all three species under both temperature regimes. All three species significantly differed in their physiological profiles (chlorophyll a, protein, lipids, carbohydrates, biomass, and δ¹³C_h-e) and had species-specific physiological responses to the individual and synergistic effects of increased wintertime temperatures and moderate nutrients. Montipora monasteriata and A. muricata increased one or more energy reserves in response to the individual effects of moderate nutrients or increased temperatures. Pocillopora damicornis shifted their trophic status toward greater photoautotrophy under the combined effects of moderate nutrients and increased temperatures. Overall, our results indicate an overall net positive species-specific physiological responses to the individual and combined effects of moderate nutrients and increased winter temperatures.