Colonization of Porphyra Perforata Thallus Discs by Pythium Marinum, A Marine Facultative Parasite

Abstract
Laboratory infections of Porphyra perforata thallus discs with zoospores of Pythium marinum showed that the colonization rate is markedly influenced by temperature, salinity, and the reproductive stage of the algal discs. The most rapid colonization rate occurred on discs obtained from reproductive areas of the alga, or areas immediately adjacent to these, when the discs were in diluted seawater with a salinity of 24%. and at 20 C. All species of Porphyra examined were capable of being infected in the laboratory as was Porphyrella gardneri.