kind of an ambiguous question. the blue whale is the largest animal, the honey mushroom is the largest fungus. a giant sequoia in California weighs 4.5 million pounds. so while the fungus covers thousands of acres, does it weight 4.5 million pounds? so what is your definition of large? this argument is discussed in a link below and the author contends that trees in the Rocky Mountains are the largest living things. i also heard that a kelp forest could be one of the "larger" living things too.
the question also arises as to whether or not something has to be "attached" to be the largest living thing or not. so the great barrier reef might be the largest living thing, the individual components are not genetically identical. so, hopefully this is an ambiguous answer to an ambiguous question.
and you can eat anything, whether you survive or not is the question.