Vernal Pools

Vernal pool as a study site for students of the Population Biology course. (Photo by Faith Forry)

I was recently caught in the thickets of final exams— the last finals week of my undergraduate career. I recently graduated from Clarion University with my Bachelor’s of Science in Environmental Biology. So, to commemorate my senior year and undergraduate studies, I would like to take some time to talk about the phenomenon of vernal pools and a particularly interesting species which can be found there.

In my Population Biology class this semester, our lab involved collecting population data for various species found in a vernal pool on local state game lands. Vernal, seasonal, ephemeral, and temporary are all names to describe pools of water which form from rain and snowmelt during certain times of the year but later disappear during the dry season. As they are not connected to other bodies of water, vernal pools are considered “isolated wetlands.” They can form in the floodplain of a river or stream, in association with another wetland in a low lying area, or in depressions of an upland area.

A gravid female Spotted Salamander being processed by students. (Photo by Faith Forry)

These temporary wetland pools are sensitive and relatively small habitats, making them easily disturbed or destroyed by human activity. Habitat loss and habitat fragmentation from land development has dramatically decreased the natural distribution and functioning of vernal pools. Pollution from agricultural, suburban, and urban runoff has degraded water quality, and changes to the water table have disturbed the natural hydrology. Climate change, as well as changes to vegetation and substrates in the pools, are also threats. In order to maintain the health, abundance, and ecological services of vernal pools in perpetuity, the identification and conservation of these essential wetland habitats is paramount.

Aside from being beautiful and teeming with life, vernal pools bear great health and environmental value for people and wildlife alike. Wetlands mitigate greenhouse gas emissions by sequestering atmospheric carbon dioxide. While reducing flooding and erosion from runoff, the gathering of surface water simultaneously recharges our groundwater. By filtering out pollutants like the phosphates and nitrates in runoff, wetlands purify our water. Vernal pools provide food and water for game animals such as bears, deer, and turkeys; bats and birds also feast on the abundance of insects found around these pools.

Being temporary, fish are not able to establish as a top predator in these pools; thus, they function as an essential breeding site for many amphibians. Wood Frogs, American Bullfrogs, Red-spotted Newts, Jefferson Salamanders, and Spotted Salamanders were just a few of the common passersby we saw during our time at the pool. Spotted Salamanders (Ambystoma maculatum) lay their eggs in large, gelatinous masses which they anchor to debris in the pool. Although it is helpful in protecting against predation, the thick jelly-like matrix enveloping the salamander eggs can make it difficult for oxygen to reach the embryos inside. Of course, nature has a unique solution. Next time, we’ll delve into the extraordinary mutualistic relationship between Spotted Salamander embryos and green algae. Until then.

You can find information about vernal pool species and their identification, best management practices for landowners, state and federal laws which protect vernal pools, and how to register a vernal pool at www.naturalheritage.state.pa.us/VernalPools.aspx.

Written by Faith Forry — May 12, 2021