08.09.17 Shoreline Spotlight
Summer is the season of rain, hurricanes, nesting shorebirds, nesting Sea Turtles and, of course, the tiny and colorful Coquina. The Coquina shells are common on the beach, sometimes piled together like dirty dishes from the aftermath of a feast of shore birds. Summer seems to be Coquina season, even though these tiny mollusks, donax variabilis, don’t get much attention. But, scoop up sand in the right place below the water and you can see and feel them actively digging into the sand in your hand. Stand a bit higher than the water and you can hear the Coquina snap pop and crackle as they try to dig in deeper.
You can find clusters of Coquina shells in the lower end of the inter-tidal zone. Go out during a mid to low tide, during the new or full moon cycles and wade into ankle deep water. Dense clusters of live Coquina are just beneath the surface and have a pebbly feel under foot. They are active, and quickly try to rebury themselves using a muscular foot that works them back into the sand. I always thought of these shellfish as inanimate, but they are very active. The dynamic nature of the intertidal zone means that things are always changing. Currents and waves churn up the sand, big tides leave creatures stranded and dry. Coquinas use the currents, and their ability to dig themselves in as a way to change locations, sometimes in search of more favorable feeding grounds. Coquina are filter feeders and help keep our waters clean. They filter out plankton, bacteria and detritus from the water, and are food for Pompano, Whiting, Shorebirds and even humans.
The presence of an abundance of Coquina is a good indicator for our beach and it’s ability to sustain life. Coquina thrive in stable, naturally formed sand. In return they filter the water and help feed our birds and sports fish. I didn’t notice the small Polycheate worm until I was looking at the photo of the Coquinas on my computer. It was identified as a possible Clam Worm, Alitta succinea, by our Town Biologist Rae Burns. They are yet another example of the vast, complex life that our beach supports because it’s not just sand it’s a living beach.
Back before WWII, when our island was sleepy, there was a Coquina canning facility on the site that the Baptist church currently occupies. That building was originally planned to be a service building for a casino, but Luke Gates made it into a canning factory when the planned casino didn’t materialize. Workers would gather the Coquina on the beach and bring them to the factory where they would make broth, which the owner claimed was a great remedy for a hangover. Could be true, when was the last time you saw a shorebird with a hangover. They could not get the cans due to the demands of WWII, and no one’s a fan of a plan for a cannery with no cans.
One of the striking features of the Coquina is their striking variety of colors from red to violet, thought to be a method to confuse predators. They are often overlooked by shellers because of their small size and abundance, but they are worth a closer look.
I noticed an interesting phenomenon the other day on the beach. There was this fine grass like plant growing in the wash. Most if the tufts were small and sparsely spaced. On closer inspection, most of the plants were attached to Coquina shells. I thought, what a smart plant! When the surf digs up the plant, the coquinas dig it back in! Rae Blake explained it to me, the plants are actually green filamentous algae growing on the Coquinas. The algae tends to appear when the salinity in the water is more reduced and the temperature is warmer during the warmer, wetter months of summer. The plants benefit from the relationship, although there is no obvious benefit for the Coquinas. This type of one sided relationship is called Commensalism. I am sure many of us have been in a similar situation in our personal lives.
So, next time you are lucky enough to be on the beach during a mid to low tide, have a look in the shallows for the pebbly little colorful Coquinas. Watch then dig themselves into the sand, maybe acting as a gardener, imagine the feast for the shorebirds and admire the variety of their colors. But, if you had a long night, stick to aspirin. Live shelling is prohibited on the beach and aspirin is easier to find since the canning factory has closed.