Oysters become habitats serving as homes
for sedentary critters such as mussels,
sponges, and barnacles. The crevices
between offer refuge to crabs and small
fish. Larger fish gather to forage among the
It was this buffet that helped sustain the
animals living within the Chesapeake for
thousands of years. People, too, have
depended on the oyster for survival. As they grow, oysters build
layers of calcium that form a
record of the conditions in which
they lived. They tell us about temperature, salinity, and oxygen levels. For instance, we know from
written accounts that oysters nourished the settlers of Jamestown
during “The Starving Time.” But
it’s the record written in shells that
tells us the colony had been suffering under the worst drought in 800 years.
Today, the oysters that grew in abundance
when the early colonists arrived are recovering from near obliteration. Over harvesting during the late 1800s and early 1900s
nearly scoured the bottom clean. By the
1920s two-thirds of the reefs were decimated. Near the end of the century, disease
and pollution depleted oyster populations
even further. The number of these crucial
shellfish plummeted to a scant few percent
of what it was when Captain John Smith
first explored the Bay.
In the last two decades, there has been a
growing movement to restore oysters in the
Bay. CBF has planted more than 200 million oysters in Maryland and Virginia
waters. Our volunteer oyster gardeners
play a big role in keeping up supply.
We give them baby oysters, which they
grow in cages hanging from piers. A year
later, the gardeners bring us their full-grown oysters for planting on sanctuary
reefs. For the most part, those reefs are the
same flat bars and beds people have come
to associate with oyster habitat. But that’s
not the natural topography of the Bay.
We now know that in order to thrive, oys-
ters need more than a hard surface on
which to attach. They need vertical scaf-
folding that allows them to grow up above
the muddy bottom. They need a world of
three dimensional structures where cur-
rents swirl around obstacles, mixing oxy-
gen into the water and carrying away silt.
Natural reefs once furnished all of that.
Efforts to restore the jewels of the
Chesapeake face a unique challenge. “The
fewer oysters you have, the fewer places
you have for oysters to grow,” said Karl
Willey, Manager of CBF’s Maryland Oyster
Restoration Center. Without reefs, it’s a
desert down there.”
What’s more, the vital habitat reefs provide
is just part of their contribution to the Bay.
Each adult spends its life filtering pollution
from the water at a rate of up to 50 gallons
per day. On the half-shell, the bivalve may
look like a creamy grey lump of meat, but
it’s actually an anatomical marvel built of
pumps and filters. As currents flow past
four rows of gills, tiny hairs filter bits of
mud and sand from the water. The hairs
wave lighter particles such as microscopic
algae (phytoplankton), bacteria, and bits of
decayed material up toward the oyster’s
mouth. Yes, they have mouths. They also
have sensory nerves that taste everything
before it enters the mouth. Anything that
doesn’t pass muster gets wrapped in
mucous and spit out. Through this
remarkable process of eating, bivalves
clean the water.
When oysters were plentiful, they could filter the entire volume of the Bay in four
days. With so few remaining today, the job
takes about a year. In addition, the diverse
community of filter feeders that live on a
healthy reef have their own role in cleaning
up the water.
For all of these reasons, oysters are essential for a healthy Bay.
It would take thousands of years to regrow
the reefs that have been destroyed. But
another solution offers literal relief for the
beleaguered oyster population. Reef balls,
concrete structures resembling large whif-
fle balls sliced in half, introduce instant
three-dimensional structure on the bottom
of the Bay. Like the nooks and crannies of
a natural reef, holes in reef balls make the
perfect home for fish and other critters that
live naturally among the oysters.
CBF has planted thousands of reef balls
throughout the Bay, each covered with
thousands of juvenile oysters. In the
Some groups have expressed concerns, however, that artificial reefs
pose a hazard for navigation and
crabbing. But the benefits of
healthy reefs and a thriving underwater
community will pay off for everyone.
Still, reef restoration is only part of the
solution. Water quality poses another challenge. Rain washes pollution from the land
into the Bay. Mud and dirt can bury oysters
living on the bottom. At the same time,
runoff from fertilizer and waste causes
blooms of algae that eventually die and
decay. The process removes oxygen from
the water, suffocating oysters.
Oysters are a complex and integral part
of a healthy Chesapeake Bay. Their
demise has come at a great cost to the
environment and the economy of the
region. But we know how to restore
them. Reducing pollution and rebuilding reefs will help oysters survive in significant enough numbers to become
self-sustaining. The oysters in turn will
help clean the water and return a
dynamic three-dimensional landscape to
the bottom of the Bay. It took a few centuries to get us where we are today. It
will take a long time to return to days of
plenty. But it can be done. The story of
the oyster’s recovery will be the story of
a cleaner Chesapeake teeming with
Kimbra Cutlip is CBF’s Senior
Mutlimedia Writer. She loves
almost anything to do with
the Bay, but she’s yet to warm
up to a plate of raw oysters.
CBF has planted more
than 200 million oysters in
Maryland and Virginia waters.
Our volunteer oyster gardeners play
a big role in keeping up supply.