We all know that the flavor of an oyster is impacted by where it is raised. But did you know that an oyster can sometimes be a different color based on where it is raised? This isn’t very common, but there are some areas where oysters will regularly take on some coloration because of the cycle of local algae. North Carolina and France both have areas where an oyster’s gills will turn green over winter because of the presence of a blue-green algae called Halsea Ostrearia. This ecological event is celebrated in France, but North Carolina is still coming to terms with it. These oysters used to be sold at a discount because people did not like the color and did not fully understand why it happened. However, the tide is turning and some farmers have begun celebrating the annual event much like they do in France.
While the Chesapeake Bay does not have an annual “green gill” event, we have something just as interesting; we call it Cinnamon Season. Every spring, we get a red algae, Myrionecta Rubra, that impacts the color of oysters in the Rappahannock. Myrionecta Rubra is a non-harmful red algae that is common along the Atlantic coast during spring and fall. It impacts different parts of the Bay at different times depending on conditions, but it is a very regular occurrence. We likely see it in the spring due to rains and subsequent runoff carrying nutrients into the water.
While Haslea pigment stains the gills of oysters, Rubra impacts our oysters a little differently. The pigment typically passes through the gills and builds up inside the oysters so the oyster typically looks normal unless you puncture it while shucking, letting the pigment flow out of the oyster; if that happens the liquor can turn anywhere from a pinkish-red to a muddy red color.
While the pigment generally passes into the oyster’s gut without discoloring the oyster, the pigment can be intense enough to stain the body of the oyster, or even the inside of the shell a little bit. Given that we’re graced with these tinted oysters annually, they’ve been given a nickname for their reddish color: Cinnamons.
If you have heard of the term “red tide,” then red algae might trigger some alarm bells for you, but feel free to turn them off. Rubra is definitely not toxic (and we always confirm it’s Rubra with the Virginia Institute of Marine Scientists). Plus, not all red algae is toxic, and not all toxic algae is red; hence, the term “red tide” is being phased out in favor of “harmful algae bloom,” or “HAB.” Both the Virginia Department of Health and the Virginia Institute of Marine Science (VIMS) check for and track HABs and have a website in which you can see current blooms, so you can rest easy and enjoy your Cinnamons. I know we will.