The color, texture, and quantity of the meat in the shell is very important to the raw oyster market and those qualities will vary with age, water quality, and time of harvest. The quality of the meat drops during the spawning season. Oysters are subject to a variety of natural predators, an environmental hazard that may be substantially reduced by cultivation and predator-control methods. Depending upon salinity, Atlantic oyster drills, thick-lipped oyster drills, rock shells, knobbed whelks, channeled whelks, and starfish all prey on oysters. Oysters are also subject to a variety of diseases and parasites, the most recently notorious being MSX, discussed infra.
Oysters provide a welcome habitat for commensal and competing organisms.
One algal species, Codium fragile, produces aveoliated branches filled with gas that may actually lift the oyster and carry it off with the tide.