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2013-02-27 / Family

In search of life in the county’s vernal pools

By Mark Battista
CONTRIBUTING WRITER


Lee (left) and Jane Hesler, who are certified Virginia Master Naturalists for a statewide program coordinated by Virginia Tech, examine a vernal pool and its contents – an egg mass that will produce spotted salamanders. Lee (left) and Jane Hesler, who are certified Virginia Master Naturalists for a statewide program coordinated by Virginia Tech, examine a vernal pool and its contents – an egg mass that will produce spotted salamanders. Vernal pools are magical, miniature worlds teeming with a diversity of life.

These ephemeral pools usually appear in the spring, hence the name vernal, which refers to the spring season. They are nourished and filled by water from rain or snow or by groundwater. And what makes them magical is their temporary nature – they usually disappear.

If you happen upon a vernal pool in spring, chances are it will be full of water and aquatic organisms. Return to the same pool in summer or early fall, and you will probably discover a dry piece of land, a low wallow or a slight depression.

“I always describe them as depressions on the landscape that fill with water and dry up on a cyclical or seasonal schedule,” says Anne Wright, assistant professor of biology at Virginia Commonwealth University (VCU) and coordinator of the Life Sciences Outreach Education. “And there’s lots of variance of that.

“They are typically not connected to other water bodies, and they don’t contain fish,” she elaborates.

The ephemeral nature of vernal pools precludes fish from living in them, which is ideal for the pool inhabitants, since otherwise they would be prey for fish.

To be considered a vernal pool, the pool must contain obligate species – species that need the pool in order to complete their life cycles.

In our area, Wright says, certain types of salamanders and fairy shrimp need vernal pools.

“Any kind of mole salamander” would be an obligate species, Wright says. “Around the Richmond and Chesterfield area, there really are only two we are going to find, and those are the spotted and marbled salamanders.”

Wright adds that wood frogs would also be considered an obligate species for our area, but “they tend to be more western and northern.”

The spotted and marbled salamanders are known as mole salamanders because of their subterranean existence. They spend almost the entire year underground or under logs feeding on insects and other invertebrates.

But for a few days, they emerge from underground and converge on vernal pools to mate and deposit eggs. The marbled salamanders mate in the fall, and the spotted salamanders mate in winter. After mating, the adults return to their underground life.

Wright has enlisted the help of the Virginia Master Naturalists chapters to help find, document and monitor vernal pools. She has provided workshops for various chapters to teach naturalists about the intricate life of these pools and to train them to document pools in the Richmond region.

For the past three years, Lee and Jane Hesler, both Master Naturalists, have been searching local woods for vernal pools. They learned about them during one of Wright’s workshops.

“We participated in searching for vernal pools in the area to help fulfill our certification requirements [for the Master Naturalist program], and we got hooked,” Lee Hesler says. Together, the Heslers have documented several dozen vernal pools.

On a cold, February morning, Jane and Lee Hesler tromp through the woods at the Radcliffe Conservation Area looking for vernal pools. A thin layer of ice tops each pool, but the cold air temperature and ice don’t deter them. They methodically examine each pool they encounter.

The Heslers tote basic equipment to document the vernal pools: a GPS unit to identify the location of the pool; a handful of Ziploc bags to collect and observe specimens; a small net to capture organisms; a magnifier, a camera, field guides and data sheets. Bundled against the cold, they also don knee-high waders.

The first pool they encounter is located just barely down the trail. Both walk slowly around the edge and peer into the water to find the larvae of mole salamanders, egg masses and even fairy shrimp.

“Got some larvae,” exclaims Lee Hesler, who finds the larva of the marbled salamander. It looks and moves just like a frog tadpole except that it has external gills. The featherlike gills are unmistakable.

The presence of the marble salamander makes it a vernal pool. On the data sheet, the Heslers record the dimension of the pool, the species observed, the water depth, the tree canopy over the pool and other information.

A mile farther down the trail, another pool is discovered. Jane Hesler immediately finds a clump of spotted salamander eggs. The mass of eggs is firm, like gelatin, and contains almost 75 eggs.

What’s fascinating, Lee Hesler says, is “the diversity of life found in the pools and the huge biomass of these little creatures, which can exceed that of all the larger animals in the forest.”

Though mole salamanders and fairy shrimp define a vernal pool, other creatures also make the pool their home.

“There are arthropods and isopods,” says Wright, recounting other species that use vernal pools. “And those are the scuds and the sowbugs. We’ve seen fingernail clams. We have seen dragonfly larvae … There are one or two types of caddisflies, lots of different kinds of beetles .... There’s a pretty diverse community.”

The transitory nature of vernal pools, which makes them unique, also makes them invisible to landowners. Many public and private landowners may have vernal pools on their land, but they may never know it.

“A lot of people don’t even know what these things are. If you don’t hit them [vernal pools] when they are going on and have somebody to sort of point things out, you would totally overlook them.”

Wright knows that for mole salamanders, the land surrounding the pool is just as important as the vernal pool. Adult salamanders spend most of their lives on the uplands surrounding the vernal pool.

“The science has shown that for the terrestrial habitat, the salamanders can range up to 1,000 feet in a circle around the pool,” Wright explains. “So that’s kind of the zone that needs to be protected…. There’s another area about 100 feet around the pool where the metamorphs tend to go and stay for about one year until they become true adults.”

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