Programa de Pós-Graduação Em Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal Do Rio Grande, Av. Itália, Km 8, Rio Grande, RS, 96203-900, Brazil.
Departamento de Oceanografia Biológica, Instituto Oceanográfico, Universidade de São Paulo, Praça Do Oceanográfico, 191, 05508-120, São Paulo, SP, Brazil; Instituto Coral Vivo, Rua Dos Coqueiros, Parque Yaya, Santa Cruz Cabrália, BA, 45807-000, Brazil.
Environ Pollut. 2021 Jan 1;268(Pt B):115892. doi: 10.1016/j.envpol.2020.115892. Epub 2020 Oct 19.
Global warming and local disturbances such as pollution cause several impacts on coral reefs. Among them is the breakdown of the symbiosis between host corals and photosynthetic symbionts, which is often a consequence of oxidative stress. Therefore, we investigated if the combined effects of thermal stress and copper (Cu) exposure change the trophic behavior and oxidative status of the reef-building coral Mussismilia harttii. Coral fragments were exposed in a mesocosm system to three temperatures (25.0, 26.6 and 27.3 °C) and three Cu concentrations (2.9, 5.4 and 8.6 μg L). Samples were collected after 4 and 12 days of exposure. We then (i) performed fatty acid analysis by gas chromatography-mass spectrometry to quantify changes in stearidonic acid and docosapentaenoic acid (autotrophy markers) and cis-gondoic acid (heterotrophy marker), and (ii) assessed the oxidative status of both host and symbiont through analyses of lipid peroxidation (LPO) and total antioxidant capacity (TAC). Our findings show that trophic behavior was predominantly autotrophic and remained unchanged under individual and combined stressors for both 4- and 12-day experiments; for the latter, however, there was an increase in the heterotrophy marker. Results also show that 4 days was not enough to trigger changes in LPO or TAC for both coral and symbiont. However, the 12-day experiment showed a reduction in symbiont LPO associated with thermal stress alone, and the combination of stressors increased their TAC. For the coral, the isolated effects of increase in Cu and temperature led to an increase in LPO. The effects of combined stressors on trophic behavior and oxidative status were not much different than those from the isolated effects of each stressor. These findings highlight that host and symbionts respond differently to stress and are relevant as they show the physiological response of individual holobiont compartments to both global and local stressors.
全球变暖和局部干扰，如污染，对珊瑚礁造成了多种影响。其中之一是宿主珊瑚和光合作用共生体之间共生关系的破裂，这通常是氧化应激的结果。因此，我们研究了热应激和铜 (Cu) 暴露的联合效应对造礁珊瑚 Mussismilia harttii 的摄食行为和氧化状态的影响。珊瑚碎片在中观系统中暴露于三种温度（25.0、26.6 和 27.3°C）和三种 Cu 浓度（2.9、5.4 和 8.6μg/L）下。暴露 4 天和 12 天后采集样本。然后，我们通过气相色谱-质谱法进行脂肪酸分析，以量化硬脂烯酸和二十二碳五烯酸（自养标志物）和顺式-高油酸（异养标志物）的变化，（ii）通过分析脂质过氧化 (LPO) 和总抗氧化能力 (TAC) 来评估宿主和共生体的氧化状态。我们的研究结果表明，摄食行为主要是自养的，在个体和联合胁迫下，无论是 4 天还是 12 天的实验，摄食行为都没有变化；然而，在后一种情况下，异养标志物增加。结果还表明，4 天不足以引发珊瑚和共生体的 LPO 或 TAC 发生变化。然而，12 天的实验表明，单独的热应激会导致共生体的 LPO 减少，而应激源的组合会增加它们的 TAC。对于珊瑚来说，Cu 和温度的单独增加会导致 LPO 的增加。联合胁迫对摄食行为和氧化状态的影响与单独胁迫的影响没有太大区别。这些发现强调了宿主和共生体对胁迫的反应不同，这很重要，因为它们显示了单个共生体隔室对全球和局部胁迫的生理反应。
