Teeming and Temporary

Visit a vibrant vernal pool to watch as spring unfolds.

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Every year, a complex, choreographed process transforms the bare branches and fallen leaves of winter into summer's lush green landscape. Spring brings changes over our heads and under our feet—including in vernal pools, which are temporary wetland habitats critical to several species' survival.

In Maryland, vernal pools typically start forming when fall rains begin in September. These pools eventually dry up and disappear in late summer, but during the rest of the year, particularly in early spring, they are teeming with life, supporting invertebrates, amphibians, reptiles, birds and mammals. We decided to take a closer look.

Listen Vernal Pool Soundscape

Immerse yourself in one of our local ecosystems by listening to life in a vernal pool, recorded at Baltimore County's Marshy Point Nature Center. Listen to our vernal pool soundscape.

Vulnerable Habitats

Vernal pools are temporary, shallow, isolated bodies of water that play an important role in maintaining hydrology and forest ecology. Vernal pools—as well as freshwater wetlands and ephemeral streams—are protected under the Clean Water Act of 1972, but in 2020, the Environmental Protection Agency weakened their protection by setting new rules that clear the way for gas pipelines and other energy infrastructure projects. This leaves these critical waterways vulnerable to pollution and development and threatens the ecosystems and animals that depend on them.

Dependent Species

Field biologists have identified more than 700 species in the northeastern United States that rely on these temporary habitats. In Maryland, species that depend on vernal pools for their continued existence include wood frogs, spring peepers, toads, spotted salamanders and other woodland salamanders. Spotted salamanders (pictured above) migrate from surrounding forest habitat to breed and lay eggs in vernal pools in early spring.

Frog Egg Masses

Vernal pools provide excellent breeding grounds for many aquatic species because of the absence of (hungry) fish. Several species of frogs, for example, lay their eggs beneath the pools' surface in large clumps. These eggs masses can contain hundreds of small round eggs. Dark embryos are surrounded by clear jelly capsules.

Salamander Eggs

Spotted salamanders lay their eggs in clusters below the surface, attached to submerged branches and vegetation. Their egg clusters are encased in a smooth, dense gel sac that typically turns milky white. These egg masses usually contain about 100 individual eggs.

Frog and Toad Tadpoles

Eggs of vernal pool amphibians hatch into an aquatic larval stage that must grow and metamorphose to a terrestrial stage before the vernal pool dries up. Frog and toad tadpoles initially have external gills that quickly get encapsulated into gill sacs. A Southern leopard frog tadpole, pictured above, is primarily herbivorous, grazing on algae with hard tooth plates.

Salamander Larvae

The spotted salamander larvae, pictured photo above, has feather-like external gills and is carnivorous, feeding on small aquatic invertebrates, small tadpoles and even other salamander larvae.

Food Web

Vernal pool species play an important role in the food web. Frogs and salamanders help control insect populations. With spring's warmer weather, predators like the Eastern ribbon snake, shown above, arrive to feed on frogs, toads, tadpoles and salamander larvae. Hawks and wading birds prey on ribbon snakes.

Seasonal Changes

As summer wears on, vernal pools shrink and dry up and the animals in them move on or burrow in the mud to estivate, a state of summer dormancy similar to hibernation in winter. By July and August in Maryland, all that remains are quiet, mud-caked depressions ringed by trees, shrubs and moss—until fall rains return.

All photos were taken by Mark Moody at Marshy Point Nature Center. Our thanks to Marshy Point Senior Naturalist/Director Ben Porter for his guidance and assistance.

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