Food web of an Antarctic midwater ecosystem

Krill do not feed by passive, continuous filtration but use area-intensive searching and various rapid feeding behaviors to exploit local high food concentrations. Chemicals alone at low concentrations, not particles, trigger feeding. Krill form dense schools that move rapidly and migrate primarily horizontally. Abrupt disruption of a school can trigger mass molting, and molts may act as decoys.

Observations made by using conventional scuba techniques reveal that abandoned larvacean houses serve as food sources for marine, planktonic copepods. Techniques have been developed for photographing these houses in the field for the first time. The abundance of larvacean houses in the open ocean indicates that they are important in pelagic food webs and as a source of particulate organic matter.