Abstract：
Deoxygenation is a growing threat to marine ecosystems, with an increase in the frequency, extent and intensity of hypoxia events in recent decades. These phenomena will pose various challenges to marine species, as it affects their survival, growth, body condition, metabolism and ability to handle other environmental stressors, such as temperature. Early life stages are particularly vulnerable to these changes. Thus, it is crucial to understand how these initial phases will respond to hypoxia to predict the impacts on marine populations and ecosystems. In this work, we aimed to evaluate the effect of oxygen (O2) availability on fitness related traits (mortality, growth and body condition), metabolism (Routine metabolic rates [RMR]) and thermal tolerance (CTmax), in early stages of Atherina presbyter, exposed for two weeks, to two O2 levels: normoxia (6.5-7.2 mg L-1) and hypoxia (2-2.5 mg L-1), through an experiment setup. Our findings showed that while low oxygen levels did not negatively impact mortality, total length, weight, or body condition (Fulton K), the larvae undergo metabolic depression when exposed to hypoxia, as an energy conservation mechanism. Furthermore, CTmax suffered a significant reduction in low O2 availability, due to the inability of the circulatory and respiratory systems to fulfill energy demands. These outcomes suggest that although early life stages of Atherina presbyter can survive under low oxygen environments, they are less capable of dealing with sudden increases in temperature when oxygen is scarce.
摘要：
脱氧对海洋生态系统的威胁越来越大，随着频率的增加，近几十年来缺氧事件的程度和强度。这些现象将对海洋物种构成各种挑战,因为这会影响他们的生存，增长,身体状况,新陈代谢和处理其他环境压力的能力，如温度。生命的早期阶段特别容易受到这些变化的影响。因此，至关重要的是要了解这些初始阶段将如何应对缺氧，以预测对海洋种群和生态系统的影响。在这项工作中,我们旨在评估氧气(O2)可用性对健康相关性状(死亡率，生长和身体状况)，代谢(常规代谢率[RMR])和热耐受性(CTmax)，在阿瑟琳娜长老的早期阶段，暴露了两个星期,到两个O2水平：常氧（6.5-7.2mgL-1）和缺氧（2-2.5mgL-1），通过实验设置。我们的研究结果表明，虽然低氧水平不会对死亡率产生负面影响，总长度,体重,或身体状况(富尔顿K)，当暴露于缺氧时，幼虫会受到代谢抑制，作为一种节能机制。此外，CTmax在低O2可用性方面显著降低，由于循环系统和呼吸系统无法满足能量需求。这些结果表明，尽管Atherina长老的早期生命阶段可以在低氧环境下生存，当氧气缺乏时，它们应对温度突然升高的能力较弱。
