Definition of "refugium"

refugium

noun
plural refugia or refugiums
1. Any local environment that has escaped regional ecological change and therefore provides a habitat for endangered species.
  Quotations
  Beetles fly, many ants send forth massive swarms of reproductive alate females and males, arachnids and insect predators emerge from their hidden refugia, and termite swarm.
  2016, Justin O. Schmidt, The Sting of the Wild, Johns Hopkins University Press, page 113
2. (aquaculture) A separate section of a fishtank that shares the same water supply, used for denitrification, plankton production, etc.