Vernal Pools
Unique and diverse ecosystems…
Vernal pools are found throughout the world, and are widespread throughout the Northeast. They are also known by a variety of other names including “ephemeral wetlands”, “temporary ponds”, and “spring ponds” being amongst the most popular.
Vernal pools are unique and very important wetland ecosystems. One feature that they all have in common is they dry up at some point in the year (usually sometime during the summer) during most or all years.
Because they dry up, vernal pools aren’t able to sustain fish populations. This is their most important feature to most animals that use vernal pools. Fish are the primary predators of lots of species that depend on vernal pools, particularly with respect to a number of amphibians and lots of different aquatic invertebrates.
Vernal pools are found throughout the Northeast in a wide variety of landscape settings. This includes within forests, in open settings (such as meadows, fields, and sand dune ecosystems), and most anywhere in between. They are even found in the most densely urbanized settings as well.
Vernal pool photo by Brett Thelen
The “typical” cycle most vernal pools exhibit in the Northeast includes filling up with water sometime in late-summer or in the fall, and then continuously hold surface water until late-spring or early-summer, often drying up for some period in the summer. Though this varies widely among pools and even within a given pool among years, depending on that year’s precipitation patterns primarily.
Wood frog egg masses by Brett Thelen
A wide diversity of animals use vernal pools. Many, such as a number of amphibians and lots of aquatic invertebrates, use it as a kind of “nursery” where they lay their eggs and where their young develop in.
Barred Owl by Brett Thelen
Other animals (such as a wide range of birds and mammals) use it as a source of water for drinking from and bathing in, and also use it for finding prey in.
Spotted Salamander by Brett Thelen
Some of the more common and widespread vernal pool breeding amphibians in the Northeast include the wood frog, spotted salamander, spring peeper, and the American toads. Adults of these species migrate down to the pools during spring from the surrounding terrestrial habitats (most often woodlands/forest) on warm, rainy nights.
Mating Wood Frogs by Nicole Freidenfelds
They then breed and lay their eggs in the pool, after which time the female returns to the surrounding woodlands to spend the rest of the year. Males often remain at/in the vernal pools for at least a couple/several more weeks, in hopes of additional breeding opportunities, after which time they too will return to the surrounding woodlands to spend the remainder of the year in.
Metamorph Spotted Salamander by Brett Thelen
The eggs then will develop, the young (larvae in the case of salamanders, tadpoles in the case of frogs/toads) will hatch, and then will grow and develop in the vernal pool over the subsequent months. If the pool doesn’t dry out before young have fully-developed, the young will then transform (termed “metamorphose”) into a terrestrial form and will leave the pool and migrate into the surrounding terrestrial environment.
Fairy shrimp (including the one on the bottom carrying eggs) by vernalpool.org
A wide diversity of aquatic invertebrates use vernal pools as well. Like amphibians, many of them use vernal pools as a habitat to lay their eggs in and where their young develop.
Dragonfly nymph by Judy Gallagher
Among some of the many different invertebrates that use vernal pools include fairy shrimp, a wide diversity of predaceous diving beetles, larval dragonflies and damselflies of many species develop there, as do larval caddisflies, mayflies, midges, and much much more!
Unfortunately, because they don’t contain water all year long, vernal pools are only afforded very limited regulatory protection. In most cases they are afforded no protection at the federal level, such as via the Federal Clean Water Act.
Much, if any, protections that they are provided are at the state- or town-/city-level. These vary quite widely depending where you are.
Fortunately, here in the Northeast we have among some of the strongest vernal pool protection regulations in the nation. Though, many of these fall short of what is needed.
One of the actions you can take is to see what your town’s/city’s vernal pool protection regulations are, and to voice your support to your local Conservation Commission for maximizing protections for these vitally important ecosystems.
Wood Frog by Brett Thelen
And equally as important as protecting the vernal pool itself, is protecting the terrestrial environment surrounding the pool. Aside from the couple/few weeks per year that adult amphibians spend in the vernal pool, they spend the rest of the year in the surrounding woodlands.