A paper in Annals of Botany shows that Utricularia (Bladderworts) trap pollen and algae as well as small animals. Aquatic bladderworts catch their prey with highly sophisticated suction traps consisting of little bladders that produce a reduced hydrostatic pressure.
A research team of the University of Vienna has screened the prey objects in more than 2,000 traps and shown that only 10% were animals whereas 50% of the prey objects were algae. In nutrient-poor habitats like peat bogs, algae were even more dominant in the prey. More than one third of the prey consisted of pollen grains from trees growing on the shore areas of the home waters. However Utricularia does not seem to select its menu; in fact, it sucks in everything small enough to enter the trap door.
What is more, plants that had successfully trapped numerous algae and pollen grains were larger and formed more biomass. More animal prey, on the other hand, led to a higher nitrogen content of the plant and to increased formation of hibernation buds,
The assumption that suction traps have to be triggered by movements of animal prey is shown to be incorrect as more than 50% of all bladders contained only non-motile prey like algae, pollen, bacteria and fungi but no animal prey able to trigger and open the trap.