The salp body is essentially a transparent tube ringed by muscle bands. Contracting them draws seawater in through an oral siphon, past a continuously secreted sheet of mucus that filters particles down to the size of bacteria, and out through an atrial siphon at the rear. The filtered food and the mucus net are both swallowed and replaced.
The consequence for ocean chemistry is significant. Salps package what they eat into dense faecal pellets that sink far faster than most plankton debris, and dead salp chains sink quickly too, so blooms can move a substantial quantity of carbon from the surface to depth.
Salps are routinely mistaken for jellyfish. They are not cnidarians at all but tunicates, closer to vertebrates than to anything that stings, and they have no stinging cells. Their bloom dynamics remain hard to predict, and how far salp abundance is shifting relative to Antarctic krill under changing ocean conditions is an active and unresolved question.