Skip Navigation

Helping Improve Water Quality in the Great Bay

Oysters In Great Bay Oyster Shell Deposit
Ray Konisky of UNH stands in front of 800 pounds of surf clam shell being stored at Portsmouth Harbor A Reef is Reborn:  surf clam shell is dispersed
from the barge into the Piscataqua River
restoration site


Every acre of oyster reef restored to Great Bay improves water quality.
More oysters means cleaner water.

State Conservationist, Rick Ellsmore, joined partners from the University of New Hampshire and The Nature Conservancy, and representatives of Senators Shaheen and Ayotte and of Congresswoman Shea-Porter on a cruise up the Piscataqua River and into Great Bay to gain an in-person view of 75 tons of shell being deposited from a barge into the Piscataqua River reef restoration site.

In the past decade water quality in Great Bay, NH has declined rapidly in-part due to nitrogen discharges from waste water treatment plants and non-point pollution.  NRCS, The Nature Conservancy, and The University of New Hampshire are restoring eight acres of wild oyster reefs in Great Bay NH, which will result in measurable improvements to water quality and lost fish habitat, like winter flounder.

Data shows that oysters are effective at removing up to 0.5 mg of Nitrogen per oyster with over 200,000 oysters per acre.  Each oyster filters 20 gallons per day and clears the water of light-blocking algae.  Oysters in the Great Bay Estuary have declined by 90%, with fewer than 50 acres of oyster reef remaining from a historic base of about 900 acres.  Nitrogen levels have increased by 42% in the past five years in the estuary, resulting in harmful algae blooms which block light devastating eelgrass beds and creating anoxic conditions in several areas of the bay during summer.  Currently several towns on Great Bay are under an EPA mandate to reduce waste water discharge of nitrogen in Great Bay.

Oyster Restoration Process