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By Elizabeth Taraski

At Ruritan and Rotary fundraising events, they are steamed and then poured on the table. At restaurants, they are often displayed on a crushed bed of ice. Whatever the preparation, the amazing oyster may have been from the Nansemond River.

These plump, sumptuous mollusks have been harvested from the river for hundreds of years. You probably consume them because they are low in calories and high in protein, vitamins and minerals. Mother Nature has another purpose for the Virginia native eastern oyster, known by its scientific name, Crassostrea virginica.

These flavorful menu items are a vital part of the ecosystem, filtering excess nutrients and pollutants out of the water. They live in reefs that protect shorelines and provide habitats for hundreds of marine species such as blue crabs, barnacles, mussels, spot and striped bass.

An adult oyster can filter up to 50 gallons of water per day when water temperatures are above 50 degrees Fahrenheit. They work earnestly removing particulate algae and sediment from the water at a rate of 2-3 gallons per hour. No wonder it takes a pull of more than 20 pounds to open the shell of a 3- to 4-inch oyster in good condition — they have an important job!

Baby oysters are spat and usually mature in one year. There is no way of telling male oysters from females by simply looking at them. While oysters have separate sexes, they may change sex one or more times during their life span. They are protandric, which means that in the first year they spawn as males, but as they grow larger and develop more energy reserves in the next two to three years, they spawn as females. An increase in water temperature triggers male oysters to release sperm and females to release eggs into the water. This begins a chain reaction of spawning which clouds the water with millions of eggs and sperm. A single female oyster produces 10 to 100 million eggs annually. When water temperatures fall over the winter, oysters cease to feed. The oysters stop filtering and seldom open their shells.

Oysters are divas and only thrive if the conditions are just right — correct water salinity range, a minimum water depth, adequate amounts of dissolved oxygen and adequate amounts of plankton. The salinity of the water will influence the growth rate of your oysters and whether they may become exposed to oyster-specific diseases. Salinity is measured in grams of salt per liter of water, or parts per thousand. Oysters require a salinity of at least 8 ppt to grow, and oyster growth increases with increased salinity. Below 10 ppt salinity, oyster growth rates are generally reduced; some oysters show intermediate growth rates at salinities between 10-20 ppt and highest growth rates at high salinities more than 20 ppt. Oyster leased grounds along the Nansemond River are regulated by the Virginia Marine Resources Commission. Oysters are most prevalent from the Route 125 up to the James River. Oysters are not found near Constant’s Wharf, where the salinity levels are negligible.

So the next time you attend an oyster roast or prepare an oyster dinner at home, take three seconds to acknowledge the significant role the delectable meaty critter has in helping our river.

Nansemond River Preservation Alliance has been serving the city of Suffolk since 2010 by educating and encouraging all citizens to be environmental stewards and work to protect the river, creeks and their tributaries. Information about our local waterways, NRPA’s projects and activities, and ways for you to make a difference can be found at www.NansemondRiverPreservationAlliance.org or cleanmyriver.com.

Dr. Elizabeth Taraski is president and chief executive officer of the Nansemond River Preservation Alliance.