Souza Taylor, Brijs Jeroen, Tran Leon, Crowder Larry, Johansen Jacob L
Hopkins Marine Station, Stanford Oceans, Stanford Doerr School of Sustainability, Pacific Grove, CA, United States of America.
Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kāne'ohe, HI, United States of America.
PLoS One. 2025 Jan 31;20(1):e0318410. doi: 10.1371/journal.pone.0318410. eCollection 2025.
Herbivorous fishes play a crucial role in the conservation of coral reefs threatened by thermal stress (e.g., marine heatwaves and long-term ocean warming) by helping to maintain reefs in a coral-dominated state via the removal of algae. However, as thermally sensitive ectotherms, rising thermal stress may also pose a serious threat to these fishes and the critical ecosystem functions they deliver. Here we evaluate the consequences of thermal stress on the capacity of a common herbivorous coral reef fish (Acanthurus triostegus) to control finely filamentous matrices of Caulerpa sertularioides and C. verticillata algae in Hawai'i, by characterizing in-vivo changes in metabolic demands, diurnal foraging rates, activity patterns and individual condition in a laboratory setting during winter (24.0±0.1°C), summer (27.5±0.1°C), and at the peak of a representative marine heatwave, (31.0±0.1°C). Rising temperatures caused significant increases in standard metabolic rate (from 135 O2 kg-1 h-1 in winter to 224 O2 kg-1 h-1 at the peak of a marine heatwave), but not in the proportion of time spent active (83-96%) or foraging (~2.4 bites min-1). Consequently, A. triostegus gained body mass during summer and winter, but lost ~0.8% body mass per day during the marine heatwave. Given marine heatwaves can last for weeks to months, these results indicate that while herbivorous coral reef fishes may continue to remove algae during periods of thermal stress, their ability to control many macroalga may be limited due to precipitous reductions in individual performance. Therefore, in addition to algal types, the thermal sensitivity in herbivorous reef fishes will need to be considered for the successful implementation of coral-algal management strategies in a warmer world.
草食性鱼类在保护受到热应激（如海洋热浪和长期海洋变暖）威胁的珊瑚礁方面发挥着关键作用，它们通过清除藻类帮助维持珊瑚礁处于以珊瑚为主导的状态。然而，作为对温度敏感的变温动物，不断上升的热应激也可能对这些鱼类及其提供的关键生态系统功能构成严重威胁。在这里，我们通过描述冬季（24.0±0.1°C）、夏季（27.5±0.1°C）以及代表性海洋热浪高峰期（31.0±0.1°C）在实验室环境下代谢需求、昼夜觅食率、活动模式和个体状况的体内变化，评估热应激对夏威夷一种常见的草食性珊瑚礁鱼类（三刺刺尾鱼）控制蕨藻和细枝蕨藻精细丝状藻体能力的影响。温度升高导致标准代谢率显著增加（从冬季的约135 O₂ kg⁻¹ h⁻¹增加到海洋热浪高峰期的224 O₂ kg⁻¹ h⁻¹），但活动时间比例（约83 - 96%）或觅食时间比例（约2.4次/分钟咬食）没有变化。因此，三刺刺尾鱼在夏季和冬季体重增加，但在海洋热浪期间每天体重损失约0.8%。鉴于海洋热浪可能持续数周甚至数月，这些结果表明，虽然草食性珊瑚礁鱼类在热应激期间可能继续清除藻类，但由于个体表现急剧下降，它们控制许多大型藻类的能力可能有限。因此，除了藻类类型外，在气候变暖的世界中成功实施珊瑚 - 藻类管理策略时，还需要考虑草食性珊瑚礁鱼类的热敏感性。
