Intraspecific variation in physiological performance of a benthic elasmobranch challenged by ocean acidification and warming

Abstract

Elucidating the combined effects of increasing temperature and ocean acidification on performance of fishes is central to our understanding of how species will respond to global climate change. Measuring the metabolic costs associated with intense and short activities, such as those required to escape predators, is key to quantifying changes in performance and estimating the potential effects of environmental stressors on survival. In this study, juvenile little skate Leucoraja erinacea from two neighboring locations (Gulf of Maine, or northern location, and Georges Bank, or southern location) were developmentally acclimatized and reared at current and projected temperatures (15, 18 or 20°C) and acidification conditions ( pH 8.1 or 7.7), and their escape performance was tested by employing a chasing protocol. The results from this study suggest countergradient variation in growth between skates from the two locations, while the optimum for escape performance was at a lower temperature in individuals from the northern latitudes, which could be related to adaptation to the local thermal environment. Aerobic performance and scope declined in skates from the northern latitudes under simulated ocean warming and acidification conditions. Overall, the southern skates showed lower sensitivity to these climatic stressors. This study demonstrates that even mobile organisms from neighboring locations can exhibit substantial differences in energetic costs of exercise and that skates from the northern part of the geographic range may be more sensitive to the directional increase in temperature and acidification expected by the end of the century.

Convergent evolution of locomotor morphology but not performance in gymnotiform swimmers

“…We corrected for body size using a scaling factor (B) determined by habitat (which was the same across all but one species, see ESM) Appendix S1, whereas a majority of single‐species studies simply divide by mass—that is use a (B) of 1. In a recent study on the little skate, where correction factors similar to those of the current study were applied, the MO 2 data are comparable to those presented here (Di Santo, ; Di Santo & Kenaley, ). In addition, during preliminary analyses, the present data were analysed using a scaling factor of 1 (results not presented), which yielded oxygen consumption results of similar scale to those seen in banded knifefish (McKenzie, Steffensen, Taylor, & Abe, ) and rainbow trout (Gerry & Ellerby, ).…”

Skating by: low energetic costs of swimming in a batoid fish

“…Consequently, skates at low speeds had an even higher COT tot if the amount of energy consumed after exhaustion is considered. This suggests that, at low speeds, skates must also rely on anaerobic pathways to fuel this activity (Di Santo, 2016).…”

“…Skates were transferred to the swim tunnel and accustomed to the experimental set-up for 2 h prior to trials. Preliminary trials revealed that oxygen consumption in little skates returns to routine levels within 2 h after exhaustion (Di Santo, 2016). Following fatigue, the fish were allowed to rest in the tunnel for at least 1 h while oxygen consumption was recorded to determine recovery rates (when Ṁ O2,rec returned to Ṁ O2,rout levels).…”

In the face of climate change and exhaustive exercise: the physiological response of an important recreational fish species

“…If species are able to physiologically tolerate these changes, they could be considered a winner in the climate crisis. These physiological tolerances can be assessed through various measurements, including aerobic scope (AS), which is generally defined as the difference between maximum and standard metabolic rates, and within which all of life's processes must occur [27][28][29]. It appears that the trend of aerobic scope over temperature varies considerably on both a species-specific [26] and individual-specific level [30], where some (species or individuals) may display a bell-shaped curve [28,31], while others show a steady increase in AS with temperature up to the species' lethal limits [26,28].…”