Behavioral responses of a coastal flatfish to predation-associated cues and elevated CO2

The direct and indirect effects of ocean acidification (OA) on marine ecosystems are a growing concern. Studies with marine fishes suggest that elevated CO2 may affect behavior by interfering with an important brain neurotransmitter. OA effects on fish behavior are comparatively understudied in temperate and boreal species. In laboratory experiments, we first characterized speckled sanddab (Citharichthys stigmaeus) behavioral responses to potential predation cues (predator odor, damaged skin cues from injured conspecifics, and sight of a predator) under ambient CO2 levels (~400 μatm). Sanddab reduced conspicuousness and foraging at the sight of a predator, but increased activity and conspicuousness when exposed to damaged skin cues. We then examined the effects of elevated CO2 levels (~900 μatm and ~1500 μatm) on posture, activity, and foraging of sanddab, and the behavioral responses to damaged skin cues. Sanddab behavior appeared generally resilient to the effects of elevated CO2 levels, but there were non-significant trends of fish from the medium CO2 treatment exhibiting lower posture and activity scores, and reduced feeding activity. The resiliency of speckled sanddab to OA conditions may be related to their distribution in a coastal upwelling region with seasonally elevated CO2 levels. Alternatively, prolonged acclimation to elevated CO2 may have mitigated the effects observed in other fishes following shorter-term exposures. Additional studies of ecologically relevant behaviors across diverse species assemblages are necessary to evaluate the impact of ocean acidification on marine food webs.