Biologists on the hunt for vernal pools at Middlesex Fells Reservation

Biologist Matt Burne makes his way up a steep, rocky trail in the Middlesex Fells Reservation. His sons, Mason, 10, and Liam, 8, follow close behind. Dark clouds fill the late afternoon sky, and thunder rumbles in the distance. Pausing atop a rocky outcropping, Burne scans the woods below.

“It’s right down here, kids,” Burne says, pointing to a small pond a couple hundred feet away, surrounded by white pines, red maples, and sweet pepperbush.

Burne carefully makes his way down the hillside to the pond. He wades a short distance into the 2-foot-deep pool, and scoops up a net full of muck from the bottom. Sifting through mud and wet, decaying leaves, he announces his finds.

“I’ve got a wood frog tadpole and a spotted salamander larva,” he says. “Proof positive it’s a vernal pool.”

Burne, vice president of the Vernal Pool Association and conservation director for the Walden Woods Project, is participating in the first formal vernal pool survey of the Middlesex Fells Reservation, which he initiated in the spring of 2012.

Vernal pools, small temporary ponds that fill with water in fall and spring and typically dry up by late summer, are found throughout Massachusetts and serve as breeding areas for a variety of amphibians, including salamanders, frogs, and toads, as well as insects and other invertebrates. Some of these animals, like spotted salamanders and wood frogs, are fairly common, while others, such as spadefoot toads and marbled salamanders, are endangered in Massachusetts. Whether rare or abundant, vernal pool organisms rely on these ephemeral wetlands as a critical part of their life cycle, making vernal pools an important conservation target.

The Middlesex Fells Reservation has 2,575 acres of conservation land spread across Malden, Medford, Stoneham, Melrose, and Winchester. With more than 100 miles of trails, and a variety of habitats including forests, meadows, ponds, streams, and rocky outcroppings, the Fells is a popular outdoor recreation spot for hikers, dog walkers, mountain bikers, and others.

The Fells has about 100 potential vernal pools, identified from aerial photographs. Burne estimates there could be another 50 potential pools that don’t show up on the photographs. He said about 24 vernal pools have been certified to date.

“This is our second field season,” he said. “We had a couple false starts in 2010 and 2011, but preliminary interest kind of fizzled. And 2012 was a funky year because of the weather, so not many pools were certified the first year.”

According to Alexandra Echandi, natural resource specialist/trail operations and development for the Massachusetts Department of Conservation and Recreation, which manages the Fells, vernal pool certification in the conservation area has only been done sporadically in the past. In 2011, the Middlesex Fells Reservation Resource Management Plan was ratified by the Stewardship Council, a citizen advisory group that works with the agency. The plan called for several cultural, natural, and recreation resource recommendations to help guide the various groups who use the Fells to designated areas, as well as certification of all vernal pools.

Matt Burne checks his net for evidence that a Middlesex Fells pond is a vernal one. Matthew J. Lee/Globe Staff

The agency works in coordination with a group of volunteers who are conducting the survey, including Burne, Joe Martinez, a curatorial assistant in the herpetology department at Harvard’s Museum of Comparative Zoology, and biologist Matt Gage and his nephew Dominic Kemmett. Echandi, who is based in the Fells, also helps certify pools. Each volunteer is assigned a specific part of the reservation.

“The Fells was divided into eight subsections by a pair of botanists doing floral surveys several years ago,” explained Burne. “We used their divisions, and assigned different sections to each participant.”

He said it’s important to locate and certify vernal pools so the conservation agency’s staff will know where pools are and can facilitate their protection. People who can have a potential impact on vernal pools in the Fells include recreational users, like hikers, dog walkers, and cyclists.

“All of us have potential impacts on pools and organisms,” Burne said. “Animals can be stepped on. Dogs in ponds can affect egg masses and larvae. All sorts of impacts come along with recreational use.”

Echandi said the Resource Management Plan recommended that buffer zones, the land surrounding vernal pools, be assessed as well, and that a priority be made to move trails and other potential disturbances at least 50 feet from a vernal pool if they were deemed to be having a negative effect.

Runoff from eroded areas like trails could deposit sediment in nearby pools, which could affect a wide variety of organisms, said Burne, especially eggs of invertebrates that are laid on pool bottoms.

But Burne said climate and environmental change may be bigger problems.

“I’m just speculating, but I was struck by the amount of algae in the pools last year,” he said.

Because these were his first visits to these pools, he couldn’t say if there has been a change, but lots of pools are dense with algae, and the biologists are not finding many amphibians in them. This could be normal in the Fells or it may represent an altered environment.

Once evidence is collected and documented, it is submitted to the Natural Heritage and Endangered Species Program, which certifies vernal pools in Massachusetts.

Two certification methods can be used. The obligate species method is easiest, Burne said, and requires documenting breeding evidence of wood frogs or mole salamanders (ambystomatids), such as egg masses, tadpoles, or salamander larvae. The presence of fairy shrimp can also be used for documentation. Obligate species depend on vernal pools to complete their life cycle, so breeding activity confirms vernal pool status.

The second method is the facultative species method, and requires evidence that species like gray tree frogs, spring peepers, or American toads are breeding in a pool, as well as proof the pool dries up later in the season. Facultative species frequently breed in vernal pools, but are capable of breeding in other types of wetlands, so their presence alone may not confirm a vernal pool.

If a body of water has facultative organisms and dries up, that’s sufficient to certify it. A dry pool provides evidence it is free of established populations of fish, which might prey on vernal pool organisms and their eggs. The fact that vernal pools are fish-free is why many vernal pool organisms breed there.

Both methods require evidence of no permanently flowing outlet from the pool, to prove there’s no year-round connection to potentially fish-bearing water bodies, Burne explained.

Burne said vernal pools are also important food resources for other wildlife, such as wading birds, snakes, turtles, and mammals like raccoons, which may feed on breeding amphibians, or their eggs and larvae.

“The certification process also helps us learn about the animal species that reside in the Fells,” said Echandi. “We don’t know of many. The wildlife inventory for this park is really weak compared to other parks in Massachusetts.”

Vernal pool organisms they have found to date include spotted salamanders, wood frogs, American toads, and spring peepers, as well as invertebrates, such as fairy shrimp.

Their most exciting find so far is the American clam shrimp, said Burne.

“It’s related to fairy shrimp and other crustaceans,” he explained. “And it’s only known from three other locations in Massachusetts” and from the southeastern United States.

This is part of the reason the vernal pool certification project is important, said Burne.

“This project is an opportunity to do something that has some value for protection of rare species and sensitive habitat,” Burne said. “The more information government agencies have, the better job they can do protecting public property.”

Don Lyman can be reached at donlyman@ix.netcom.com.