Combined effect of pCO2 and temperature levels on the thermal niche in the early benthic ontogeny of a keystone species

MANRÍQUEZ, PATRICIO H.; JARA, MARÍA ELISA; GONZÁLEZ, CLAUDIO P.; DÍAZ, MARÍA ISABEL; BROKORDT, KATHERINA; LATTUCA, MARÍA EUGENIA; PECK, MYRON A.; ALTER, KATHARINA; MARRAS, STEFANO; DOMENICI, PAOLO

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2020 vol. 719

0048-9697

In order to make robust projections of the impacts of climate change on biota, it is critical to understand how abiotic factors interact to constrain the distribution and productivity of organisms. We evaluated the effects of projected, near-future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of the Chilean false abalone (Concholepas concholepas) a coastal, benthic keystone species and an exploited natural resource. Three separate trials of an experiment were conducted exposing small juvenile C. concholepas for 1 mo to one of two contrasting pCO2 levels (~500 μatm and ~1200 μatm). In addition, each pCO2 level was combined with one of two temperature treatments. The control temperature was 15°C, whilst the other temperature treatments used were 10°C (Trial 1), 20°C (Trial 2) and 25°C (Trial 3). At the end of each trial, we assessed Critical Thermal maxima (CTmax) and minima (CTmin) via self-righting success, calculated partial thermal tolerance polygons, measured somatic growth, determined transcription of heat shock protein 70 (HSP70) and measured oxygen consumption rates. Regardless of the pCO2 level, transcript levels of HSP70 were significantly higher in small juveniles after chronic (1 mo) exposure to extreme temperatures (10°C and 25°C) indicating physiological stress. Oxygen consumption rates significantly increased with increasing temperature from 10°C to 20°C but was not affected by pCO2 or the interaction between both factors. Oxygen consumption rates measured at 25°C were significantly lower than those at 15°C. Juveniles exposed to present-day and near-future pCO2 levels at 20°C showed similar thermal tolerance polygonal areas; whilst changes in both CTmin and CTmax at 25°C and 10°C caused narrower and broader thermal tolerance polygonal areas, respectively. In summary, temperature affected specific growth rate, oxygen consumption and transcript levels of HSP70 in small juvenile C. concholepas. Moreover, exposure to elevated pCO2 did not affect thermal tolerance, growth rate or oxygen consumption at acclimation temperatures within the thermal range normally experienced by juveniles of this species in northern Chile (15°C to 20°C). At elevated pCO2 conditions, however, exposure to warmer (25°C) or colder (10°C) temperatures reduced or increased the thermal area, respectively. This study demonstrates the importance of examining the edges of thermal tolerance to better understand how OA and temperature will combine to physiologically challenge inter-tidal organisms.