SAV Savvy

Where can one find soft shell crabs, sea horses, queen conches, and pipefish all on a sunny afternoon? In one of the Chesapeake Bay’s beds of Submerged Aquatic Vegetation (SAV for short).

SAV are sometimes called simply “underwater grasses” and are some of the unsung heroes of our beloved Bay. These plants cannot survive outside of water, and spend their days happily submerged under the surface, where water supports them and enough sun penetrates; they spend all their energy growing while filtering water. Thus, SAV add to the oysters’ efforts in cleaning the waters of the Bay. But that’s only the start to the marvels SAV provide.

ShoreRivers is well aware of the importance of SAV. ShoreRivers is an environmental nonprofit whose mission is to restore and protect Eastern Shore waterways through science-based advocacy, education, and restoration. One of its “prime directives” is to assist the multi-state initiative to improve the SAV situation in the Bay.

“SAV is one of the easiest ways to understand the health of the Bay: when grasses thrive, other species follow suit,” says Rebecca Murphy, Education and Volunteer Coordinator for ShoreRivers. It’s true; it’s like a childhood rhyme, “The Bay is Alive Where SAV Thrive.”

SAV are Shangri-La for virtually all of our favorite Bay creatures. Sea horses can only live in amongst the waving fronds. Queen Conches spend their entire lives there, too, but many more of our favorite Bay creatures use the cover provided as a nursery, hiding in the beds only in their youth. Red Drum, grouper, flounder, and other fish use the cover these lovely grasses provide to grow to maturity, as do Penaeid Shrimp and Spiny Lobsters. Our beloved crabs love SAV as well.

Riverkeeper Matt Pluta displays healthy SAV.

Blue crabs are utterly vulnerable when they molt and have no shells. They’ll swim for miles to find a good bed of SAV to disappear in until their new shell hardens. Tiny baby crabs may live there for months, eating even smaller crustaceans that also thrive in what must appear, to a thumbnail sized animal, as large and busy as New York City does to us.

SAV are necessary, not only for healthy crab catches, but are integral to the health of the entire Bay and its seafood industry. In fact, the disappearance of eelgrass in the past century nearly drove Chesapeake Bay Scallops into extinction. The scallops were a common harvest until 1933, when the Chesapeake-Potomac hurricane uprooted and drowned most of the area’s eelgrasses. Disease was already rampant, wiping out many beds where the little scallops live, and had already shrunk the harvests. This was followed by an almost “perfect storm” of SAV destruction, including increasing sediment and pollution, more hurricanes, invasive mute swans that eat SAV, invasive seagrass species that outcompete our native SAV… this drove SAV populations so low it seemed the scallops could not possibly recover. There were so few some thought them extinct. It’s possible that many of us have never even have heard of them.

Populations of crabs, fish, ducks, herons, and other SAV loving creatures shrank, too, while geese took to lawns and farmers’ fields, where they could find edible grasses. The scallops are not extinct, although many thought they were. The massive effort to bring back healthy SAV beds allows hope for those little bivalves who, like oysters, filter and clean the water.

Galvanized by the presumed extinction of the once numerous scallops and struggles of other wildlife for which the Bay was justly famous, large scale mapping of SAV beds and replanting efforts began. Since 1984, the Virginia Institute of Marine Science (VIMS) has performed aerial surveys to determine where, how big, and how many SAV beds exist in the Bay. Ground based surveys are performed by various groups – many are volunteers – to interpret the aerial survey data as it is frequently difficult to determine from the air whether or not some sections are SAV beds or simply extremely turbid shallow water.

“Ground based” surveys also allow determination of what sort of SAV is growing in any particular SAV bed. Some species of underwater grasses come from other places and, lacking the creatures that eat them in their own native waters, outcompete our native SAV.

“Ground surveys are not only vital to verifying and providing additional detail to VIMS’ aerial surveys, but they also provide a fantastic opportunity for residents to take a closer look at their rivers and the clear benefits that SAV provides to them,” Rebecca commented.

Determined efforts to replant SAV followed the aerial surveys. It’s trickier than it seems at first; varying salt levels in the Bay mean that some species can only be planted in saltier sections while others need fresher water. Then the probability of their survival must be factored in – while SAV do help prevent erosion by holding soil in place, until they’re established, the entire mass can be swept away easily. Widgeon grass, for reasons of its own, seems to exist in boom and bust cycles – so it’s best to plant it in small amounts surrounded by hardier varieties (in the mid-Bay, with moderate salt levels). The National Atmospheric Administration (NOAA), the Nature Conservancy, Virginia Coastal Management program and the Virginia Institute of Marine Science have invested more than $6 million into restoring these beds.

This SAV bed is located right off the dock of an area homeowner.

All this hard work has paid off. The 2017 surveys showed that, for the first time since aerial mapping began, more than 100,000 acres of SAV were thriving in the Bay. Hopes are high that the Bay will once again be vigorous.

The scallops are having a comeback, too, now that there are good sized beds of SAV to live in. Chesapeake Bay Scallops lie on the soil, instead of burying themselves, so they have a particular need for the coverage the seagrasses provide. Like the Blue Crabs, these are pretty creatures, with grey, reddish, purple and brown shells. Regardless of their shell color, they have 30 to 40 bluish eyes around the edges of their shells. These scallops are rather small, no bigger than three inches, but, oh, how tasty.

Volunteer monitor Mike Fleagle records his SAV discoveries.

Those who’ve worked so hard to bring back this once nearly extinct animal – carefully breeding them in safety, planting SAV, formulating “cages” to protect them from predators while the SAV worked on making their own comeback – think the goal of harvesting them someday might be in sight. Perhaps within 10 years, we may find them on the menu.

Want to help? Become a SAV survey volunteer. “Ground” surveys are a little like a scavenger hunt. There’s no need for a big boat; a kayak, canoe, rowboat or even inflatable allows one to join the fun. Find some SAV, snap a picture, or mark it on a chart, and give the information to ShoreRivers, who will add your input to the database. Congratulations. You are now part of a growing phenomenon called “Citizen Science.”

Citizen Science is just what the name implies – observations and data from laypeople. All over the world, people from all walks of life are recording their observations, providing scientists with data from many places that would otherwise be inaccessible to them. This gives us all the opportunity to add to the world’s wisdom.

What is particularly important is discovering exactly which types of SAV are growing in a bed since it cannot be determined from an aerial survey. We are lucky to count 15 native species of SAV in the Bay. The most common are eelgrass, widgeon grass, wild celery, redhead grass and sago pondweed. ShoreRivers will provide training to people interested in being a SAV Volunteer Monitor. For more information, contact Rebecca Murphy at

Written by Maureen “Reenie” Rice, a Master Gardener in Talbot County. A lifelong naturalist, Ms. Rice enjoys writing and research when she’s not playing in the dirt.

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