Abstract
Levels of dissolved carbon dioxide (CO2) projected to occur in the world’s oceans in the near future have been reported to increase swimming activity and impair predator recognition in coral reef fishes. These behavioral alterations would be expected to have dramatic effects on survival and community dynamics in marine ecosystems in the future. To investigate the universality and replicability of these observations, we used juvenile spiny chromis damselfish (Acanthochromis polyacanthus) to examine the effects of long-term CO2 exposure on routine activity and the behavioral response to the chemical cues of a predator (Cephalopholis urodeta). Commencing at ~3–20 days post-hatch, juvenile damselfish were exposed to present-day CO2 levels (~420 μatm) or to levels forecasted for the year 2100 (~1000 μatm) for 3 months of their development. Thereafter, we assessed routine activity before and after injections of seawater (sham injection, control) or seawater-containing predator chemical cues. There was no effect of CO2 treatment on routine activity levels before or after the injections. All fish decreased their swimming activity following the predator cue injection but not following the sham injection, regardless of CO2 treatment. Our results corroborate findings from a growing number of studies reporting limited or no behavioral responses of fishes to elevated CO2.Significance statementAlarmingly, it has been reported that levels of dissolved carbon dioxide (CO2) forecasted for the year 2100 cause coral reef fishes to be attracted to the chemical cues of predators. However, most studies have exposed the fish to CO2 for very short periods before behavioral testing. Using long-term acclimation to elevated CO2 and automated tracking software, we found that fish exposed to elevated CO2 showed the same behavioral patterns as control fish exposed to present-day CO2 levels. Specifically, activity levels were the same between groups, and fish acclimated to elevated CO2 decreased their swimming activity to the same degree as control fish when presented with cues from a predator. These findings indicate that behavioral impacts of elevated CO2 levels are not universal in coral reef fishes.
Highlights
Ocean acidification, caused by increased levels of dissolved carbon dioxide (CO2) (Caldeira and Wickett 2005; Doney et al 2009), is expected to affect the fitness of marine organisms, especially if CO2 levels reach those predicted for the year 2100 in a business-as-usual emission scenario (i.e., ~1000 μatm) (Ishimatsu et al 2008; Dupont et al 2010; Heuer and Grosell 2014)
Following 80–82 days of exposure to present-day or elevated CO2, we commenced experiments to investigate whether spiny chromis exposed to high CO2 differed from control fish in their routine activity levels as well as in their behavioral response to predator chemical cues
Impaired predator avoidance should result in reduced survival in fishes exposed to high CO2, which has been reported in experiments in which coral reef fish were exposed to elevated CO2 for 4–12 days and tested in control water (Munday et al 2010; Ferrari et al 2011a, b; Munday et al 2012; Chivers et al 2014)
Summary
University of Tasmania and CSIRO Agriculture and Food, Hobart, Tasmania, Australia. Behav Ecol Sociobiol (2017) 71: 108 levels. Activity levels were the same between groups, and fish acclimated to elevated CO2 decreased their swimming activity to the same degree as control fish when presented with cues from a predator. These findings indicate that behavioral impacts of elevated CO2 levels are not universal in coral reef fishes.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
