Combined effects of ocean acidification and salinity on foraging behaviour of intertidal scavenging gastropod Nassarius festivus

Chemoreception is crucial to marine scavengers in food acquisition. The combined effect of salinity (10 psu, 30 psu) and ocean acidification (380 μatm, 950 μatm and 1250 μatm) on food detection at three foraging distances (20 cm, 40 cm and 60 cm) was studied in a marine scavenging gastropod Nassarius festivus over an exposure period of seven days. Time and percentage of individuals reaching the bait (excised clams) were recorded. Lower salinity increased food searching time at all distances away from the bait on both Day 1 and Day 7. Higher pCO₂ levels increased food searching time at 20 cm and 60 cm on Day 1, but 40 cm and 60 cm on Day 7. The interactive effect between pCO₂ and salinity was only significant on Day 1 at 20 cm. Lower salinity reduced percentage of individuals engaged in foraging at all distances away from the bait on both Day 1 and Day 7. The effect of pCO₂ was significant at 60 cm on Day 1, but at all distances on Day 7. The interactive effect between pCO₂ and salinity was only significant on Day 1 at 20 cm. In conclusion, food detection ability was negatively affected by low salinity and high pCO₂ with the inhibitory effect of pCO₂ being stronger as the time of exposure increased.