When the Going Gets Tough, the Females Get Going: Sex‐Specific Physiological Responses to Simultaneous Exposure to Hypoxia and Marine Heatwave Events in a Ubiquitous Copepod

• Published in: Global change biology Vol. 30; no. 10; pp. e17553 - n/a
• Main Authors: Vermandele, Fanny, Sasaki, Matthew, Winkler, Gesche, Dam, Hans G., Madeira, Diana, Calosi, Piero
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-10-2024
• Subjects: Animals; Aquatic crustaceans; Climate Change; Copepoda - physiology; Egg production; Environmental changes; Exposure; extreme events; Extreme Heat - adverse effects; Female; Females; Heat waves; High temperature; Hot Temperature - adverse effects; Hypoxia; Hypoxia - physiopathology; Life History Traits; Male; Males; Marine heatwaves; Marine organisms; Metabolic rate; metabolic rates; Metabolism; multiple stressors interaction; oxygen; Physiological effects; Physiological responses; Physiology; Plankton; Population dynamics; Sex; Sex Factors; Survival; temperature; Temperature tolerance; thermal limits; Thermal stress; extreme events; temperature; metabolic rates; oxygen; thermal limits; multiple stressors interaction
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/gcb.17553

ABSTRACT
The existence of sex‐specific differences in phenotypic traits is widely recognized. Yet they are often ignored in studies looking at the impact of global changes on marine organisms, particularly within the context of combined drivers that are known to elicit complex interactions. We tested sex‐specific physiological responses of the cosmopolitan and ecologically important marine copepod Acartia tonsa exposed to combined hypoxia and marine heatwave (MHW) conditions, both of which individually strongly affect marine ectotherms. Females and males were acutely exposed for 5 days to a combination of either control (18°C) or a high temperature mimicking a MHW (25°C), and normoxia (100% O2 sat.) or mild hypoxia (35% O2 sat.). Life‐history traits, as well as sex‐specific survival and physiological traits, were measured. Females had overall higher thermal tolerance levels and responded differently than males when exposed to the combined global change drivers investigated. Females also showed lower metabolic thermal sensitivity when compared to males. Additionally, the MHW exerted a dominant effect on the traits investigated, causing a lower survival and higher metabolic rate at 25°C. However, egg production rates appeared unaffected by hypoxia and MHW conditions. Our results showed that MHWs could strongly affect copepods' survival, that combined exposure to hypoxia and MHW exerted an interactive effect only on CTmax, and that sex‐specific vulnerability to these global change drivers could have major implications for population dynamics. Our results highlight the importance of considering the differences in the responses of females and males to rapid environmental changes to improve the implementation of climate‐smart conservation approaches.
This study explores whether males and females of an ecologically important copepod differ in their ability to withstand the isolated and combined effects of hypoxia and marine heatwave events. We report that males appear more vulnerable than females to the conditions tested, providing first‐hand evidence of the importance of considering sex‐specific responses. Additionally, we show that the marine heatwave condition in isolation and not the combined condition had the strongest impact on the traits measured.