Periwinkles like mycelial spaghetti . Dew permits snails to climb . There is at least one other snail that eats naturally-decaying marshgrass. Baby snails can be colorful . At least one crustacean also grazes decaying marshgrass.
Amphipods can very selectively grab fungal stuff .
There are two species of crabs that are suspects as saltmarsh-fungal grazers. The marsh-edge squareback eats mushrooms when it roams into the edge of the forest. Here's a reconfigured saltmarsh model that explicitly recognizes fungi and their grazers. Some fungi may be able to fend off grazers. There are tiny microsnails in the saltmarsh sediment that may also be sinks for fungal mass.