The release of chemicals following herbivore grazing on primary producers may providefeeding cues to carnivorous predators, thereby promoting multitrophic interactions. Inparticular, chemicals released following grazing on phytoplankton by microzooplanktonherbivores have been shown to elicit a behavioural foraging response in carnivorouscopepods, which may use this chemical information as a mechanism to locate and remainwithin biologically productive patches of the ocean. In this paper, we use a 1D spatialreaction-diffusion model to simulate a tri-trophic planktonic system in the water column,where predation at the top trophic level (copepods) is affected by infochemicals releasedby the primary producers forming the bottom trophic level. The effect of theinfochemical-mediated predation is investigated by comparing the case where copepodsforage randomly to the case where copepods adjust their vertical position to follow thedistribution of grazing-induced chemicals. Results indicate that utilization ofinfochemicals for foraging provides fitness benefits to copepods and stabilizes the systemat high nutrient load, whilst also forming a possible mechanism for phytoplankton bloomformation. We also investigate how the copepod efficiency to respond to infochemicalsaffects the results, and show that small increases (2%) in the ability of copepods tosense infochemicals can promote their persistence in the system. Finally we argue thateffectively employing infochemicals for foraging can be an evolutionarily stable strategyfor copepods.