The effect of environmental calcium on olfactorymediated predator-prey interactions in pumpkinseed sunfish (Lepomis gibbosus)

At this time calcium concentrations of lakes within the boreal region of the world and particularly within Canadian Shield lakes across northern and central Ontario are declining. The base cation Ca2+ is important in activating olfactory neurons in many vertebrates and low environmental Ca2+ has been found to disrupt olfaction. In this study we investigated the effects of calcium decline on the olfactory-mediated behavioural responses of pumpkinseed sunfish (Lepomis gibbosus). In separate field experiments, we exposed juvenile sunfish to conspecific injury-released alarm cue, and food cue in both Plastic Lake and Blue Chalk Lake. We then tested adult sunfish response to juvenile conspecific injury-released alarm cue, and visual stimuli. All of the experiments conducted at Plastic Lake were also repeated with Ca2+ concentrations increased to match Blue Chalk Lake. It has been demonstrated that under low Ca2+ (~ 1 mg/L), response to juvenile conspecific injury-released alarm cue was impaired. In response to food cue there was no significant attraction at Plastic Lake under low or elevated Ca2+ concentrations, there was also no significant attraction under the Ca2+ concentration tested at Blue Chalk Lake. Additionally, after examining adult responses to chemical and visual cues they showed no change in response to alarm cue under any of the Ca2+conditions tested at both Plastic and Blue Chalk Lake. Adults only showed a visual preference in the low Ca2+ concentration tested at Plastic Lake. Our results indicate that calcium decline negatively impacts the olfactory-mediated anti-predator responses of pumpkinseed sunfish. Interruptions in olfactory-mediated behaviour may have major ramifications on aquatic community structure and ecosystem productivity.