The "jelly" that coats the developing spawn is there to protect it. The spawn is more vulnerable after its developed into tadpoles, if fish are in the pond, they will certainly eat some.
I once saw a grass snake clear a whole pond of spawn.
If you've got newts in your pond they'll eat the very tiny tadpoles which hatch out from the spawn. Otherwise birds will come to the edge of your pond where tadpoles come to suck up the algae and eat them (particularly blackbirds and magpies in our garden). And if you've got fish, they'll eat the baby tadpoles too.