Almost twenty of us braved the clouds and chill this afternoon to meet at Quinnebaug Woods in Holland, a Trustees of Reservations property, for a quick introduction to vernal pools. Jen Ohop, President of Opacum Land Trust, introduced Matt Burne, a vernal pools specialist who led us on a short walk to our study site. He waded right in
and scooped up these critters for us to admire:
Matt, Vice-President of the Vernal Pool Association, was a goldmine of information about these fascinating environments. He told us that in Massachusetts there are tens of thousands of vernal pools, many more than you might think. In 1999-2000, a state survey was conducted in order to determine just how many there are. Scientists pored over the aerial photographs taken during the survey and came up with a number close to 30,000. Early spring, before the trees leaf out, is the best time to look for these often ephemeral bodies of water from above, though of course a coniferous tree stand will distort the picture because the cameras cannot see through evergreen cover. The survey data were eventually transferred into the Massachusetts GIS system and can be studied online. According to the Mass Division of Fisheries and Wildlife website, as of January 2009, the Natural Heritage and Endangered Species program had certified around 5,024 vernal pools.
So, what are vernal pools? According to the VPA website:
A vernal pool, because of its periodic drying, does not support breeding populations of fish. Many organisms have evolved to use a temporary wetland which will dry but where they are not eaten by fish. These organisms are the “obligate” vernal pool species, so called because they must use a vernal pool for various parts of their life cycle. If the obligate species are using a body of water, then that water is a vernal pool. In New England, the easily recognizable obligate species are the fairy shrimp, the mole salamanders and the wood frog.
In our pool, we were thrilled to see signs of all three obligate species. In my photo, the fairy shrimp (Eubranchipus vernalis), the spotted salamander (Ambystoma maculatum) egg mass, and the wood frog (Rana sylvatica) egg mass are clearly visible (the other creatures in abundance in our water sample are mosquito larvae).
Matt told us that a vernal pool is ideal for studying the interdependence of species in an ecosystem. There is heavy dependence on leaf litter, and the species which populate these pools are detritivores, herbivores (frogs), and carnivores (salamanders). The salamanders have life cycles of 10-12 years, whereas the wood frogs live only between 1-2 years. The salamander eggs hatch into larvae with a month or two, then the juveniles migrate to the uplands by September; these mole salamanders live in small mammal burrows underground during their adult phase, and 90% return to their natal pools to breed in the spring. The wood frog eggs also hatch into larvae within a month, then the larvae transform within two months into adults. There is lots of predation, from the amphibians eating mosquitoes, to snakes, raccoons, and owls eating the amphibians; survival rates of any egg might be as low as 1%. Biologists have also documented symbiotic algae living in the amphibian egg masses.
I think it’s safe to say that we simply don’t yet know very much about the lives of these tiny creatures. Because of the pace of development in our state, protecting these unique habitats should become a priority.
