DURHAM — Population growth and climate change are major stressors on Great Bay, but efforts are underway to restore ecosystems in the beloved body of water often dubbed New Hampshire’s “hidden coast.”

A 2018 report prepared by the Piscataqua Region Estuaries Partnership (PREP) shows both the Great Bay and Hampton-Seabrook estuaries have declined in recent years.

Shellfish are at extremely low levels compared with populations in the 1980s and early 1990s. Natural habitats for clams in Hampton-Seabrook and oysters in Great Bay are close to being completely decimated, according to the report.

Also, eelgrass in Great Bay shows an overall decline and a clear deterioration in its ability to recover from episodic stress, the report says.

“One of our biggest challenges is it looks beautiful so unless you know what’s going on behind the scenes, you don’t know the system is really struggling,” said PREP Director Rachel Rouillard said.

Coastal Science Program Manager Kalle Matso compared the bay to a family member who appears to to be in tip-top shape but is struggling from a number of life-threatening conditions. The question is, which condition should scientists concentrate on treating at any given time?

Matso used the example of global warming and nitrogen loading. Warming waters are hard to control on the local level, but nitrogen loading is something that can be worked on because 33 percent of nitrogen comes from wastewater treatment facilities and the remaining 67 percent comes primarily from septic systems, fertilizer and animal waste.

“It’s a mixing bowl. Sometimes, you have to work harder on one thing because you can’t fix the other. We have to be more stringent on the things we can control,” Matso said.

Seven rivers from 42 New Hampshire and 10 Maine communities drain into the Great Bay watershed, which comprises 1,023-square-miles. That means every resident in the region is contributing either directly or indirectly to the health of the ecosystem, Rouillard said.

“We all have a responsibility as people who live on the watershed. Whether you’re in Wakefield or Eliot (Maine) or Kingston, what you do in your backyard has an impact,” Rouillard said.

Homeowners are encouraged to maintain their septic systems; dispose of pharmaceutical drugs, paint and chemicals responsibly; never pour car fluids down the drain; and clean up pet waste.

Residents living in the Great Bay region can also participate in an oyster reef restoration program run by The Nature Conservancy and University of New Hampshire.

So far, The Nature Conservancy. has 89 sites and 300 volunteers locally. Oyster conservationist volunteers get a cage with oyster spat and from mid-July to early September they grow oysters off their docks and record data. People as young as 9 or as old as 80 can help.

“It’s a great way to build education about the health of Great Bay,” said Brianna Group, an oyster conservation cooridinator.

In early October, the “oyster nannies” are taken out to place juvenile oysters on top of restoration sites. The program is so popular, 75 of the participants last year signed up for this growing season.

The oyster conservationist program is a part of overall efforts by The Nature Conservancy to create a network of oyster reefs which will help to improve water quality and provide a habitat for juvenile fish and other invertebrate creatures.

Coastal and Marine Director Alix Laferriere said they now have a 28-acre footprint in the bay. Their oysters are grown at Jackson Estuarine Laboratory in Durham before being placed in nature.

“This year, we put about 800,000 oysters on the reefs,” Laferriere said.

Laferriere said they build restoration reefs near native reefs to help support them. Eight of their 11 sites are in Great Bay.

According to materials from The Nature Conservancy, a single oyster can filter as much as 30 gallons of water a day, removing nitrogen and other nutrients that threaten the health of the ecosystem.

In an overview of Great Bay Estuary on the New Hampshire Department of Environmental Services website, officials describe it as unique because it is both a saltwater and freshwater system set apart from the coastline.

The U.S. Environmental Protection Agency has afforded special protection to Great Bay as one of only 28 “estuaries of national significance.”

To learn more about becoming an oyster conservationist, visit {a href=”https://www.nature.org/en-us/about-us/where-we-work/united-states/new-hampshire/oyster-restoration-in-the-great-bay-estuary/?vu=r.v_nhoysters” target=”_blank”}www.nature.org/NHoysters{/a}.Anyone interested in becoming a citizen scientist to help with research on the Seacoast can visit {a href=”https://seagrant.unh.edu/crv” target=”_blank”}www.seagrant.unh.edu/crv{/a}.