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A Year in the Life of Pimmit Run: Vernal Pools

Updated: Mar 28

I have a confession to make. This time of year, when it feels as if spring is taking forever to arrive, I love visiting the vernal pools that crop up here and there in small depressed areas along the Pimmit Run Stream Valley forest floor. I like to see what forms of life appear in them. They are muddy, and not everything in them is pleasant to see. But they are evidence of the cycle of life that is nature. So I can often be seen near the pools, watching and waiting.

Me iin My Muck Boots on the Edge of a Vernal Pool

Vernal pools are ephemeral wetlands. They fill up as it rains and groundwater rises. They become dry (usually) over the course of the year. And they thus provide a temporary, usually fish-free, habitat for amphibian and invertebrate species, including wood frogs and salamanders, to breed and evolve.


This stretch of middle Pimmit Run has lots of vernal pools -- on one cold day in early March I come across at least ten. Most dry out eventually, but some maintain at least some water for many months. Below are some of the vernal pools along the stream valley.


As I explore the vernal pools this time of year, I am always in search of frog and salamander egg masses. One fine March morning I was rewarded with the sight of two frog egg masses in one of the vernal pools along the stream valley. The sun was shining on them like a spotlight. And the blue sky reflected in the murky water, suggesting the expanse of the universe.

Wood Frog Egg Masses in a Vernal Pool in Early March

To actually observe frogs and salamanders is a special delight. While we often hear frogs along the stream valley, particularly on spring evenings, we don't often see them. So it was pretty special to come across a wood frog sunning itself in a vernal pool in the middle of an unusually warm day this March. Maybe it was thawing out from its winter deep freeze. It is said that a small vernal pool may have several thousand wood frogs visiting it and living within a few hundred feet of the pool. Pretty amazing that we rarely observe them. Here is the wood frog observed in early March.


As it gets warmer, the number of frog egg masses and adults multiplies daily. What was a still muddy pond a few days ago becomes a vibrant incubator and frog playground in the course of hours. Watch the video and you can see a pair of adults and hear their distinctive sounds.



Fallen leaves play an important role in vernal pools. They provide the nutrients and energy that nourish the frogs and salamanders of nearby woodlands. They also are just plain beautiful. Its easy to lose track of time watching a leaf slowly glide along in a vernal pool.


Not everything found in vernal pools is familiar or even attractive. And often there are reminders that we live in an environment filled with invasive species and pollutants. Here is a rogues gallery of vernal pool inhabitants observed on my travels: Left: most likely Trentepohlia aurea, a species of green algae that is most assuredly not green; middle: Chain tunicate, an aquatic being composed of individual parts; and Pectinatella magnificas, otherwise known as Magnificant Bryozoan, or Moss Animals. Hmm.


Wishing there was more green in this post, but that will come next month!



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