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<p>This study examined how carbon and nitrogen assimilation and exchange shift under normal and elevated temperatures in three cnidarian-dinoflagellate symbioses involving <i>Exaiptasia diaphana</i> (Aiptasia) with either the native symbiont <i>Breviolum minutum</i> or the non-native symbionts <i>Breviolum psygmophilum</i> or <i>Durusdinium trenchii</i>. Carbon was provided as <sup>13</sup>C-bicarbonate and nitrogen as <sup>15</sup>N-ammonium, nitrate, dissolved free amino acids and <i>Artemia salina</i> nauplii. At control temperature, symbionts differed in carbon fixation—<i>B. minutum</i> achieved the highest rate of population-level carbon fixation, <i>D. trenchii</i> showed higher <i>per</i>-cell photosynthesis but low population-level production due to its low density, while <i>B. psygmophilum</i> had similar <i>per</i>-cell photosynthesis to <i>B. minutum</i>, but lower population-level production. <i>Artemia salina</i> feeding was associated with a higher rate of photosynthetic carbon fixation relative to incubation with dissolved nitrogen. Across the different host-symbiont pairings, photosynthesis unexpectedly increased at 32&#xa0;°C, while nitrogen pathways shifted: for the hosts and their symbionts, ammonium assimilation rose substantially and dissolved free amino acid uptake stayed stable or declined, while the hosts relied more on heterotrophic nitrogen. The C:N ratio of <i>B. minutum</i> significantly increased, suggesting signs of increased nitrogen limitation, while the C:N ratio of <i>D. trenchii</i> decreased, likely due to an increased reliance on heterotrophic nitrogen. <i>B. psygmophilum</i> decreased carbon transfer to the host, whereas <i>D. trenchii</i> maintained carbon translocation. Notably, host nitrogen retention increased with temperature across all nitrogen treatments in <i>B. minutum</i>. These species-specific patterns highlight how thermal stress reshapes nutrient dynamics differently across symbiont types, with implications for long-term host-symbiont compatibility.</p>

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The influence of symbiont identity and nitrogen source on the thermal disruption of carbon and nitrogen cycling in a model cnidarian-dinoflagellate symbiosis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月26日

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  • Oscar Crehan,
  • Christine Ferrier-Pagès,
  • Renaud Grover,
  • Simon K. Davy

摘要

This study examined how carbon and nitrogen assimilation and exchange shift under normal and elevated temperatures in three cnidarian-dinoflagellate symbioses involving Exaiptasia diaphana (Aiptasia) with either the native symbiont Breviolum minutum or the non-native symbionts Breviolum psygmophilum or Durusdinium trenchii. Carbon was provided as 13C-bicarbonate and nitrogen as 15N-ammonium, nitrate, dissolved free amino acids and Artemia salina nauplii. At control temperature, symbionts differed in carbon fixation—B. minutum achieved the highest rate of population-level carbon fixation, D. trenchii showed higher per-cell photosynthesis but low population-level production due to its low density, while B. psygmophilum had similar per-cell photosynthesis to B. minutum, but lower population-level production. Artemia salina feeding was associated with a higher rate of photosynthetic carbon fixation relative to incubation with dissolved nitrogen. Across the different host-symbiont pairings, photosynthesis unexpectedly increased at 32 °C, while nitrogen pathways shifted: for the hosts and their symbionts, ammonium assimilation rose substantially and dissolved free amino acid uptake stayed stable or declined, while the hosts relied more on heterotrophic nitrogen. The C:N ratio of B. minutum significantly increased, suggesting signs of increased nitrogen limitation, while the C:N ratio of D. trenchii decreased, likely due to an increased reliance on heterotrophic nitrogen. B. psygmophilum decreased carbon transfer to the host, whereas D. trenchii maintained carbon translocation. Notably, host nitrogen retention increased with temperature across all nitrogen treatments in B. minutum. These species-specific patterns highlight how thermal stress reshapes nutrient dynamics differently across symbiont types, with implications for long-term host-symbiont compatibility.