Olivares-Cordero Daniel, Timmons Courtney, Kenkel Carly D, Quigley Kate M
Department of Biological Sciences University of Southern California Los Angeles California USA.
Minderoo Foundation Perth Western Australia Australia.
Ecol Evol. 2025 Jan 12;15(1):e70839. doi: 10.1002/ece3.70839. eCollection 2025 Jan.
Coral reefs worldwide are threatened by increasing ocean temperatures because of the sensitivity of the coral-algal symbiosis to thermal stress. Reef-building corals form symbiotic relationships with dinoflagellates (family Symbiodiniaceae), including those species which acquire their initial symbiont complement predominately from their parents. Changes in the composition of symbiont communities, through the mechanisms of symbiont shuffling or switching, can modulate the host's thermal limits. However, the role of shuffling in coral acclimatization to heat is understudied in coral offspring and to date has largely focused on the adults. To quantify potential fitness benefits and consequences of changes in symbiont communities under a simulated heatwave in coral early life-history stages, we exposed larvae and juveniles of the widespread, vertically transmitting coral, to heat stress (32°C) and tracked changes in their growth, survival, photosynthetic efficiency, and symbiont community composition over time relative to controls. We found negative impacts from warming in all fitness-related traits, which varied significantly among larval families and across life-history stages. Larvae that survived heat exposure exhibited changes in symbiont communities that favored symbionts that are canonically more stress tolerant. Compared to larvae, juveniles showed more rapid mortality under heat stress and their symbiont communities were largely fixed regardless of temperature treatment, suggesting an inability to alter their symbiont community as an acclimatory response to heat stress. Taken together, these findings suggest that capacity for symbiont shuffling may be modified through ontogeny, and that the juvenile life stage may be less flexible and more at risk from climate warming in this species.
由于珊瑚-藻类共生体对热应激敏感，全球珊瑚礁正受到海洋温度上升的威胁。造礁珊瑚与甲藻（共生藻科）形成共生关系，包括那些主要从其亲本获得初始共生体补充的物种。通过共生体洗牌或转换机制，共生体群落组成的变化可以调节宿主的热极限。然而，在珊瑚后代中，洗牌在珊瑚对热的适应性中的作用研究不足，迄今为止主要集中在成年珊瑚上。为了量化在模拟热浪下珊瑚早期生活史阶段共生体群落变化的潜在适应性益处和后果，我们将广泛分布的垂直传播珊瑚的幼虫和幼体暴露于热应激（32°C）下，并跟踪它们相对于对照组的生长、存活、光合效率和共生体群落组成随时间的变化。我们发现变暖对所有与适应性相关的性状都有负面影响，这些影响在幼虫家族和不同生活史阶段之间有显著差异。在热暴露中存活下来的幼虫，其共生体群落发生了变化，有利于那些通常更耐胁迫的共生体。与幼虫相比，幼体在热应激下死亡率更高，而且无论温度处理如何，它们的共生体群落基本固定，这表明它们无法改变共生体群落作为对热应激的适应性反应。综上所述，这些发现表明，共生体洗牌的能力可能会在个体发育过程中发生改变，并且在这个物种中，幼体生活阶段可能灵活性较差，更容易受到气候变暖的影响。
