It may look like just a puddle in the woods, but this is a very specialized wetland habitat, a habitat that is quickly disappearing from the Lower Susquehanna River Watershed. It’s a vernal pool—also known as a vernal pond or an ephemeral (lasting a short time) pool or pond.
Viable vernal pools have several traits in common…
They contain water in the spring (hence the name vernal).
They have no permanent inflow or outflow of water.
They typically dry up during part of the year—usually in late summer.
They are fish-free.
They provide breeding habitat for certain indicator species of forest-dwelling amphibians and other animals.
They are surrounded by forest habitat that supports the amphibians and other vernal pool species during the terrestrial portion of their life cycle.
To have a closer look at what is presently living in this “black leaf” vernal pool, we’re calling on the crew of the S. S. Haldeman to go down under and investigate.
Along the surface of the pool we’re seeing clusters of amphibian eggs, a sign that this pond has been visited by breeding adult frogs and/or salamanders during recent weeks.
Amphibian eggs and the white tail filaments of an invertebrate of interest, Springtime Fairy Shrimp (Eubranchipus vernalis), an endemic of vernal ponds.
Let’s take it down for a better look. Dive, all dive!
Algae provides food for the shrimp and other inhabitants of the pool. Leaf litter furnishes hiding places for the pool’s many inhabitants.
These loose clusters of eggs appears to be those of Wood Frogs, a vernal pool indicator species.
Clusters of Wood Frog eggs, the embryos within those in the center of the image less developed than those to the left.
More Wood Frog eggs. Hatching can take anywhere from two weeks to two months, depending on temperature.
Wood Frog eggs with developing larvae (tadpoles) plainly visible. The green color of the eggs is created by a symbiotic algae, Oophila amblystomatis, a species unique to vernal pools. The algae utilizes the waste produced by the developing embryos to fuel its growth and in return releases oxygen into the water during photosynthesis. Upon hatching, the tadpoles rely upon the algae as one of their principle food sources.
A zoomed-in view showing development of the larvae and what appears to be a tiny invertebrate clinging on the white egg in the upper right. White eggs don’t hatch and may be infected by a fungus.
Wood Frog eggs and Springtime Fairy Shrimp.
Wood Frog eggs and Springtime Fairy Shrimp.
Springtime Fairy Shrimp swim upside-down. Note the small, bluish clusters of eggs attached to the abdomens of these females. Springtime Fairy Shrimp live their entire lives in the vernal pool. After being deposited in the debris at the bottom of the pool, the eggs will dry out during the summer, then freeze and re-hydrate before hatching during the late winter.
A damselfly larva consuming fairy shrimp. (Visible in the margin between the uppermost lobes of the dark-colored oak leaf to the right.)
Getting in close we see A) the damselfly larva eating a Springtime Fairy Shrimp and B) one of several discarded exoskeletons of consumed shrimp near this predator.
A fishfly larva (Chauliodinae). Mosquito numbers are kept in check by the abundance of predators in these pools.
Springtime Fairy Shrimp and a Marbled Salamander (Ambystoma opacum) larva. The presence of these species confirms this small body of water is a fully-functioning vernal pool.
Springtime Fairy Shrimp and two more larval Marbled Salamanders. The salamanders’ enlarged gills are necessary to extract sufficient oxygen from the still waters of the pool.
The Marbled Salamander is one of three species of mole salamanders found in the Lower Susquehanna River Watershed. All breed in vernal pools and live their air-breathing adult lives under the leaves of the forest in subterranean tunnels where they feed on worms and other invertebrates. Photos of an adult Marbled Salamander and the other two species, Spotted Salamander (Ambystoma maculatum) and Jefferson Salamander (Ambystoma jeffersonianum), can be found by clicking the “Amphibians” tab at the top of this page.
Marbled Salamanders lay their eggs during the fall. If the bed of the pool is dry at breeding time, the adult female will remain to guard the eggs until rain floods the pool. The eggs hatch upon inundation, sometimes during the winter.
Marbled Salamanders, like all amphibians that develop in vernal pools, must complete transformation into their air-breathing terrestrial life stage before the pool dries up in the summer heat.
A larval Marbled Salamander explores the bottom of the pool.
A larval Marbled Salamander, Wood Frog eggs, and Springtime Fairy Shrimp, it’s an abundance of life in what at first glance may appear to be just a mud puddle.
We hope you enjoyed this quick look at life in a vernal pool. While the crew of the S. S. Haldeman decontaminates the vessel (we always scrub and disinfect the ship before moving between bodies of water) and prepares for its next voyage, you can learn more about vernal pools and the forest ecosystems of which they are such a vital component. Be sure to check out…
If you are a landowner or a land manager, you can find materials specifically providing guidance for protecting, restoring, and re-establishing vernal pool habitats at…
Wasted Effort-A pair of Wood Frogs mating in a dried-up vernal pool.
First there was the Nautilus. Then there was the Seaview. And who can forget the Yellow Submarine? Well, now there’s the S. S. Haldeman, and today we celebrated her shakedown cruise and maiden voyage. The Haldeman is powered by spent fuel that first saw light of day near Conewago Falls at a dismantled site that presently amounts to nothing more than an electrical substation. Though antique in appearance, the vessel discharges few emissions, provided there aren’t any burps or hiccups while underway. So, climb aboard as we take a cruise up the Susquehanna at periscope depth to have a quick look around!
Brunner Island as seen from the east channel.
Close-in approach to emergent Water Willow growing on an alluvial Island.
The approach to York Haven Dam and Conewago Falls from the west channel.
A pair of Powdered Dancers on a midriver log.
Watertight and working fine. Let’s flood the tanks and have a peek at the benthos. Dive, all dive!
American Eelgrass, also known as Tapegrass, looks to be growing well in the channels. Historically, vast mats of this plant were the primary food source for the thousands of Canvasback ducks that once visited the lower Susquehanna each autumn.
As is Water Stargrass (Heteranthera dubia). When mature, both of these native plants provide excellent cover for young fish. Note the abundance of shells from deceased Asiatic Clams (Corbicula fluminea) covering the substrate.
A three-tailed mayfly (Ephemeroptera) nymph and a several exoskeletons cling to the downstream side of a rock.
This hollowed-out stick may be a portable protective shelter belonging to a Comb-lipped Casemaker Caddisfly larva (Calamoceratidae). The larva itself appears to be extending from the end of the “case” in the upper right of the image. Heteroplectron americanum, a species known for such behavior, is a possibility.
In the Susquehanna and its tributaries, the Rusty Crayfish (Faxonius rusticus) is an introduced invasive species. It has little difficulty displacing native species due to its size and aggressiveness.
A Rusty Crayfish.
Summers with conditions that promote eelgrass and stargrass growth tend to be big years for Virginian River Horn Snails (Elimia virginica). 2022 appears to be one of those years. They’re abundant and they’re everywhere on the rocks and gravel substrate in midriver. Feeding almost incessantly on algae and detritus, these snails are an essential component of the riverine ecosystem, breaking down organic matter for final decomposition by bacteria and fungi.
Bits of debris suspended in the flowing water streak by this Virginian River Horn Snail. The spire-shaped shell is a streamlining adaptation for maneuvering and holding fast in the strong current.
A young Virginian River Horn Snail following a mature adult. Note the green algae growing among the decaying plant and animal remains that blanket the river bottom.
Two of a population that may presently include millions of Virginian River Horn Snails living downstream of Conewago Falls.
Virginian River Horn Snails with Lesser Mystery Snails (Campeloma decisum), another native species commonly encountered at Conewago Falls and in surrounding waters.
A River Snail (Leptoxis carinata), also known as a Crested Mudalia, hitching a ride on a Virginian River Horn Snail. The two species are frequently found together.
A River Snail cleaning the shell of a native freshwater Unionidae mussel, Lampsilis cariosa, commonly called the Yellow Lampmussel or Carried Lampmussel. Because of their general decline in abundance and range, all Unionidae mussels are protected in Pennsylvania.
The Banded Darter (Etheostoma zonale) is a member of the perch family (Percidae).
A Smallmouth Bass in strong current.
Along the edge of an alluvial island at midriver, Cyprinella (Spotfin or Satinfin) Shiners gather in the cover of an emergent stand of Water Willow. The closely related Spotfin Shiner (Cyprinella spiloptera) and Satinfin Shiner (Cyprinella analostanus) are nearly impossible to differentiate in the field.
A breeding condition male Cyprinella (Spotfin or Satinfin) Shiner.
A juvenile Channel Catfish.
We’re finding that a sonar “pinger” isn’t very useful while running in shallow water. Instead, we should consider bringing along a set of Pings—for the more than a dozen golf balls seen on the river bottom. It appears they’ve been here for a while, having rolled in from the links upstream during the floods. Interestingly, several aquatic species were making use of them.
River Snail cleaning a golf ball.
A golf ball used as an anchor point for silk cases woven by Net-spinning Caddisfly (Hydropsychidae) larvae to snare food from the water column.
A Creeping Ancylid (Ferrissia species), a tiny gastropod also known as a Coolie Hat Snail, River Limpet, or Brook Freshwater Limpet, inhabits the dimple on a “Top Flight”.
A closeup view of the Creeping Ancylid. The shell sits atop the snail’s body like a helmet.
We now know why your golf balls always end up in the drink, it’s where they go to have their young.
Well, it looks like the skipper’s tired and grumpy, so that’s all for now. Until next time, bon voyage!