Symbiotic Relationships in the Tundra

Lichen is an example of symbiosis in the tundra. Lichen is a plant that's make up of a type of fungus and a type of alga. The fungus makes up over 90% of the lichen plant body. Algae produces food through photosynthesis and the fungus gives the alga water and minerals that it collects from the ground surface.  Both the algae and the fungus benefits from this relatinoship.  Is it mutualism, commensalism, or parasitism?