Bearded seals are important predators of benthic mollusks, crustaceans, fish, and octopi. They compete with other seal species for food; however walruses tend to be their main food competitor. Bearded seals are also a secondary prey to polar bears (ringed seals are primary prey). Bearded seals also serve as prey to killer whales and walruses.
Bearded seals are the only know definitive host of the nematode Pseudoterranova decipiens, which resides in the animal's stomach and intestinal lumen. The parasitic nematode is transmitted when the seal eats the' intermediate host of the parasite, American Plaice (Hippoglossoides platessoides). The bearded seal also hosts the nematode Contracaecum osculatum, which also resides in the stomach.
Numerous trematode species reside in the pancreas and bile duct of the bearded seal, and other parasitic worms reside in the intestine. Abundance of these parasites varies among individual seals.
Protozoan parasites like Sarcocystis species (residing in the tongue) and Giardia species, such as Giardia duodenalis, are often found in the gut of the bearded seal. The protozoan species of Giardia found in bearded seals are not the same species of Giardia that can be transmitted to humans.