Sand smelt larvae's resilience to hypoxia and implications for thermal tolerance

• Published in: The Science of the total environment Vol. 950; p. 174969
• Main Authors: Almeida, João, Lima, André R.A., Faria, Ana Margarida, Lopes, Ana Rita
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.11.2024
• Subjects: Atherina presbyter; Climate change; Fish larvae; Fish physiology; Oxygen availability; Climate change; Fish larvae; Fish physiology; Oxygen availability; Atherina presbyter
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.174969

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. [Display omitted] •Hypoxia did not alter weight, total length and body condition.•A metabolic depression was observed in conditions of reduced oxygen availability.•Hypoxia reduced thermal tolerance.