High p CO 2 habitats and their populations provide an unparalleled opportunity to assess how species may survive under future ocean acidification conditions, and help to reveal the traits that confer tolerance. Here we utilize a unique CO 2 vent system to study the effects of exposure to elevated p CO2 on trait‐shifts observed throughout natural populations of Astroides calycularis , an azooxanthellate scleractinian coral ende...