Lichens can actually break down rock. These crustose lichens are part of a community of organisms that colonize surface like this (you can also see mosses covering a part of the rock). But they are actually eating the rock - or in more geologic terms - breaking it down through a form of biological weathering. In this case the fungal part of the lichen secretes acids that start to very slowly dissolve the rock and absorb the nutrients that are released. But nutrients are not enough. It is the algal part of the lichen also captures the sun's energy through photosynthesis. Each doing their part to ensure the survival of the whole.
(October 2022)