Ocracoke nature, flora & fauna

Jewels of the seaside: Coquinas in the surf

Jewel-like coquinas feed at the waters’ edge. Photo: C. Leinbach

For Ocracoke news, click here

By Pat Garber

Walking along the Ocracoke beach in late spring, watching the waves roll in and out, I noticed an array of small, colorful wedge-shape mollusks.

They appeared each time the waves withdrew, as if by magic, and then disappeared back into the sand, leaving tiny holes, until the next wave again worked its magic.

One of my earliest Outer Banks memories was the discovery of these multi-hued, jewel-like creatures known as coquinas. Also known as bean clams, coquinas are small edible saltwater clams found along the shores of tropical and temperate oceans worldwide. They are among the most abundant macro-invertebrates in the intertidal zone during spring and summer, when there may be as many as 1,000 per square meter. They can often be seen at low tide.

There are dozens of species of these marine mollusks. The ones found on southeastern United States beaches, known by the scientific name Donax variabillis, can migrate vertically and horizontally with changes in the tide. Their shells measure less than one inch, and have radiating bands of various colors.

These mollusks are considered an important indicator species, their presence or lack thereof being a sign of the health of the intertidal or littoral eco-zone.  They form an important link in the food chain as filter feeders, syphoning small organisms from the surf through their gills. On these gills are hair-like filaments called cilia which produce a current which extracts the food and releases clean water. Coquinas have an incurrent syphon which takes in oxygen and food, and an excurrent syphon which offloads waste. They filter out pollutants from the water and contribute to cleaner beaches in a process called pollution dilution.

They are a food source for a number of species, including fish such as pompano and whiting, shore birds such as Ruddy Turnstones and plovers, and ghost crabs, moon snails and olive shells.

They are also considered a delicacy by human beings. Indigenous people ate them in former times, and today in this country they are the base for coquina chowder and soup. According to Green Deanee, author of Critter Cuizine, “ounce per ounce there is probably no more delicious seafood than coquina. The problem is getting an ounce…” In Italy they are served over pasta as “arselle,” and in France with garlic and parsley as “telline.”

Colorful coquinas. Photo: C. Leinbach

Coquinas typically live from several months to a year. They have a continuous reproductive cycle beginning in the spring and continuing through fall. After their death their shells eventually disintegrate to form sedimentary sandstone or limestone, such as the Coquina Outcrop found at Fort Fisher, N.C.  Coquina sandstone has been mined for centuries and is still used as a building material.

While coquinas are abundant and are not considered endangered now, there is concern about what the future may hold. Beach renourishment projects can bury coquinas under tons of sediment, decimating populations which may take up to two years to recover. Sea walls and groin construction can negatively affect their numbers, sand dunes and stabilizing vegetation being preferable ways to maintain shorelines. Climate change, which may lead to rising seas and beach erosion, could be the greatest challenge in the future.

I have never tried coquina stew, and my preference is to leave the live coquinas where they are, to simply watch and enjoy. I do, however, occasionally pick up the empty shells, still held together by strong ligament. With their vibrant colors and their triangular shaped shells they resemble butterflies, no doubt the reason that one of their common names is “butterfly shell.”  Watch for them next time you stroll along the water’s edge at low tide, and rejoice at these tiny miracles of nature.

Categories: Ocracoke nature, flora & fauna

Tagged as: