Cascading effect of grazer signalling molecules on marine phyto- and bacterio-plankton. Signals of the Sea

Copepodes are the most abundant pelagic marine grazers in temperate waters and can consume up to 30% of the daily primary production. Selective grazing by copepods cascades through the food web and shapes phytoplankton community composition and functioning. While such consumption-mediated trophic cascades are common in ecology, it has now become clear that grazers also can cause ecosystem-wide changes by inducing behavioural changes in their prey. Recently it was discovered that copepodamides, molecules released from copepods, may have this effect in planktonic food webs. The molecules have the potential to induce defensive traits in microalgae, including toxin production, cryptic behaviour, and morphological defences. This suggests that signalling compounds can induce cascading effects in the plankton community, an idea with wide implications that has never been experimentally tested.