Winter melt, spring rain create unique habitats
By Jody Heaston, IMN State Coordinator
Something magical happens every spring in many woodlands.
As the snow melts and early spring rains fall, water gathers in shallow depressions and is retained due to non-porous soils in the same area every year. The water doesn’t stay long, usually evaporating by June. These temporary aquatic habitats are called vernal pools.
Vernal pools are wetlands that fill up annually but typically dry out during part of the year. Typically found in a wooded setting, they occur in many types of depressions (natural and manmade) across the landscape. Vernal pools have varying hydrological cycles that prevent the establishment of permanent fish populations, which determine the biological community present. These shallow wetlands do not have a permanent inlet or outlet of water flow.
Vernal pools are a type of wetlands. Over 85% of Indiana’s wetlands are gone. That is upsetting considering wetlands improve water quality, hold flood waters, are an excellent educational tool, provide habitat to hundreds of species, including migratory birds, and offer the only home to many species like the fairy shrimp.
Wetlands help water quality by allowing the water to settle slow. Wetland plants take up toxins and the soil filters and removes pollutants. The water retention for wetland habitat is 1.5 million gallons of floodwater retained in one acre. That is a lot of flood control!
When walking in the woods March-April, you will often hear the chorus of frogs and spring peepers that call the vernal pools home. Many animals have adapted their life cycles to the temporary aquatic habitat. Animals that require temporary aquatic habitats for reproduction and development of their young are called vernal pool indicator species. These animals also benefit from the dry phase, because it prevents year-round water-dependent animals like fish from living in the pools. Fish prey heavily on eggs and larvae, and without seasonal pools some species would not be able to compete and reproduce.
Salamanders are an example of an animal that uses vernal pools to lay their eggs, which hatch quickly. The larval stage is then allowed to grow safely in the venal pool. Eighty-five percent of vernal pool amphibians return each year to breed in the pond where they were born. Other species, such as fairy shrimp and clam shrimp, leave eggs in the bottom of the pool that can withstand drying out in the summer and freezing in the winter. Then the eggs hatch in the spring after the water fills the depression. It is amazing all the life that is in a vernal pool when you take time to look into the waters of this wetland.
During the summer-winter seasons, one would never know there was such a magical area of life and sounds. Take advantage of spring season to hear and explore these amazing wetlands!
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